How efficient is this Army generator? MEP-831A

[@TrackGeeks]

Some interesting discussion on the video. Here are some of my thoughts. Cost comparison vs volume comparison - I personally think a volumetric comparison is the right way to go for this type of video. Since fuel cost varies across different regions and times, you can calculate costs as they relate to you in both location and time very easily. If the video referenced only cost, the content may appear less relevant to people in other parts of the world or to someone watching the video next year when prices are different. The beauty in this approach is a quart is still a quart tomorrow as it is still a quart on either coast of the USA. The conversion from quarts to liters (or whatever volume measurement is dominant in your area) is not a hard one. Plenty of places to find the conversion equations. Maybe David could have given the both the imperial and metric volumes. I see that as improvement to make the information more universal. To the efficiency topic, the tests as being done in this series of videos bring everything down to common elements. Sure, maybe the term "efficiency" could be used in a better and in more specific context but.. Using volume of fuel converted into units of battery energy removes any discussion about the "magic" that happens between the incoming fuel and energy stored in the batteries. Discussions about volumetric efficiency of pumping systems, effects of compression ratios on engine efficiency, and energy density of fuel, are fun but do you really need them in this context? There are more than a few videos on YT already going over how IC engines work and differences in fuels used in them. The “Driving for Answers” channel is one to browse if you want to explore the details on the workings of ICEs. Lets be honest, what really matters to most of us is how much fuel goes into one side and how much energy goes into the battery on the other side. This video shows that relationship in wonderfully simple, clear, and relatable terms. Strictly my opinion.

[@DavidPozEnergy]

Exactly what I was driving at with this video, and others on my channel. Thanks.

[@Subgunman]

Today for most individuals can get a metric conversion on line by asking Google.

[@Gamer-nc8qp]

@@Subgunman its still great to have while watching the video for the continuity of things

[@the1chainsawguy]

You stole that mep. They sell @ auction for 5000$. 5 years ago a 1000$. But that is excellent info

[@mondavou9408]

You are one of my trusted sources! Thank you.

[@curmudgeinnak]

Great info. I have been looking at the 6.5kw version. We are remote in Alaska and can get the fuel cheaper than gas if we buy in bulk. I have a Yanmar L90 but the engine is slowly kicking the bucket. I need something that will run my work shops as well as charge the batteries for the house and cabin. Keep the videos coming please.

[@Desertjoe789]

Love it. Seriously considering one of these. So much better than gas generators.

[@ThePaulv12]

Bit of a long post but I have some generator findings and I'm a mechanic. I live on generator power with no battery storage. I have a generator very similar to this. Since I'm on 240v @50hz, it runs at 3000rpm. It's also enclosed, has a 22lt fuel tank with electronic control and is rated at 7kva. The fuel consumption is amazing. There's no getting away from the fact, it really is very good for the power output. The problem with these generators is engine life. You get about 3000hrs. I'm on my second engine and it's at 2900hrs. I have a load bank for setting the governor and general fault diagnosis and I can no longer get the poor thing to make rated power LOL. It now makes makes 5500w that's it. Some findings, the power is very dirty and the frequency regulation is terrible. For charging a battery bank it could be good as part of having solar panels and you use it less than 250-500hrs a year. Re charging battery banks, Jesse at Solar Solution points out generator sizing is very simple. You size the generator to the load to get the most out of your fuel. If you can take 100a into your battery bank, you need a generator capable of delivering 100a continuous (+ a bit of headroom I'd say so a generator able to make 110a continuous). It's very difficult to argue with since if you have a smaller generator using less fuel it still uses more fuel charging for longer than a generator sized correctly to the load. I will add, to get the most out of your fuel you need a good quality generator. The moment you cheap out, the generator fuel consumption rises dramatically. A 10kw 4 cylinder cheap Chinese generator with brushes might consume at full load 2 lts an hour more than a mid priced Chinese generator with a better engine and a brushless alternator. Over 10 hours that's tons more fuel. For a long life generator, I ditched the air cooled single cylinder Yanmar and got a 5kva 3 cylinder liquid cooled Mitsubishi with a brushless alternator and a proper governor. It only turns at 1500rpm. The fuel consumption is pretty good. 50hrs a week average it uses about 40-50 litres depending on the time of year, however 95% of the time it is running less than 1000w in the warmer months and in the cooler months runs at about 2500w about 70% of the time increasing the fuel consumption to a guaranteed 50lts/week. I will say this, In some ways I wish I had bought a 4 cylinder generator. The fact of the matter is if you go 4 cylinder for a similar power rating you lose in fuel consumption because you have 1 more cylinder extra in engine pumping losses to pay for in fuel - meaning fuel consumption increases at all loads. But the problem is 3 cylinder engines vibrate. The vibration is a fore aft rocking couple that can only be managed not eliminated. It way better than a single, but still pretty bad. Long term, the cabinet door latches wear out, brackets crack, bolts come loose, this sort of thing. Upside is the fuel consumption is pretty good. Battery charging and living directly off generator power are conflicting applications. There is no perfect generator for living directly, since a generator is either too big (poor fuel consumption), too small (not enough power), or just right (too much fuel consumption and not enough power when you need it). One realizes what a luxury having mains power is, as you only use what you need and if it breaks someone else fixes it. You do grow to hate generators that's for sure. Charging a battery bank you can get it pretty right, just size a mid priced generator to the load. A good mid priced generator should get you 20,000hrs life and a supply of spare parts.

[@offgridinthepacificnorthwe3210]

Greetings David. I have been using the MEP-016D diesel generator since 2015, it also has the Yanmar L70 engine. We are 100% Off Grid. I did a similar test back in 2015. Off road fuel was $1.98 I was able to make 1 kilowat for $.36 cents. The MEP-016D Is not a inverter type life yours but is very fuel efficient and robust. It will put out 4k all day though it is only rated for 3k . In my opinion the L70 Yanmar is the most fuel efficient I have come across. The BTU in diesel is higher than gas along with no road tax it is a winner for sure. I will be doing another test with a propane generator. By the way the inverter generators are only more efficient when you have variable loads. For you and I we are charging large battery banks at fixed loads. There are times when I charge our batteries using the Magnum inverter/charger and pass through AC loads to the house at the same time . In cases like this I do use a gasoline inverter generator. Nice test brother. Have a blessed night.

[@DavidPozEnergy]

Thanks for your comment. Sounds like you have a nice setup.

[@NoelBarlau]

Your content is always right up my alley, David. Well done once again, and thank you. You do the kind of testing I'd be doing if I allowed myself the time. Sigh... Maybe someday.

[@DavidPozEnergy]

Thank you.

[@sasha_kahlo]

Thanks for sharing this info!

[@stevenfrazier8939]

Glad to see another video

[@jimmurphy5355]

Interesting - that works out to a little over 50 cents per kWh. High compared to grid power prices in most of the USA, but actually a bit lower than the peak rate where I live in Northern California. In theory, it would be cheaper to run that diesel generator than be on grid during those hours.

[@rongray4118]

We are in Reno, Nevada... I was thinking the same thing.

[@D2O2]

Yeah, now compare that to the cost per kwh for a solar system.

[@hardrout17]

For an European price comparaison: army generator is 2.10 Kwh/L of diesel. As of Jan 2024 in France, gas station diesel is around 1.8€/L (Its 7.4$/gal!) without road taxes its 1.35€/L. Final price is around 0.85€/Kwh (or 0.64€/Kwh without road taxes). Electricity from the grid average price is 0.25€/Kwh. 🙃

[@sn0isle]

Don't forget maintenance on the generator.

[@alexjeffs7092]

Is that with California diesel prices? I know the prices varies greatly state to state

[@GoingOffGrid101]

that diesel generator is what my red diesel was modeled off of, it looks almost the same - the inverter. it was rated at 6.5kwh lol could do 5.5kwh but was to small for my house so I purchased a 11000w Yamaha with a 3 cylinder Kubota engine. with I could of kept that little diesel :D. great test.

[@AG4KN]

As a battery charger ONLY, it will work pretty good; if you try to power the 'whole load' with that gen, you will be disappointed. I used those things in the Army and watched them catch fire for no reason. Keep several fire extinguishers handy and place it further away from structures you don't want to burn down. Good Luck finding spare parts for this generator!

[@highdesertdrew1844]

I'm sure there were reasons, determining what those reasons were was the hard part.

[@walkertongdee]

No reason for a Yanmar to burn diesel is safe, likly you guys didn't maintain it, like many military personnel lol. If it started in an electrical fire I'd bet somebody overloaded it,.3,000 watt output isn't much.

[@anttihuttula6547]

Looking the persons in military, it is not very surprising, that everything is burning and demolished. Not the brghtest ones there.

[@marginbuu212]

@@walkertongdee sadly, this is true. There's a specialized job just for that in the army but just because you're a dedicated generator mechanic doesn't necessarily mean you're mechanically inclined or know what you're doing. Sometimes people will pick jobs just because they sound cool or it means they get to stay out of combat.

[@WiSeNhEiMeR-1369]

Thanks COOP ...

[@scubaspi]

Now imagine the efficiency during winter if you had a water cooled generator or an exhaust heat exchanger which could heat your garage, workshop, or home.

[@MoaningGit]

Interesting comment, it would be great seeing David do something like this

[@mvansumeren4313]

Cogeneration units are commercially available, but unfortunately not in the US. Honda made their MCHP (Micro Combined Heat & Power) units for the Japanese market back in ~2012. The keywords for these types of systems are cogeneration and CHP for those interested.

[@juhajuntunen7866]

There is generators for tractor pto, so it only need more pipe and plumber work to harvest every Joule from fuel.

[@elelegidosf9707]

Very interesting. Your content is like a video version of Popular Mechanics - very impressive.

[@PG-ji6vq]

In fairness to the Honda, I believe you will get much better efficiency if you run your Honda generator at its continuous rating, I think this is 5.5KW. The auto throttle improves fuel efficiency on low loads but can’t mask the overall mechanical and heat losses. The fact you can finely tune the generator load is really good. If you have chance it would be great to see a Honda rematch….

[@juhajuntunen7866]

Every engine has some rpm/load compination where it is the most energy efficient. Low load=much of mechanical waste, high load=not perfect fuel burning

[@HarryT9]

What you can’t argue about is his hair … looks so good you would think it’s fake!!!

[@braddofner]

Just found your channel. I like the no frills editing approach. Old school KZbin style. Plus, you are knowledgeable and charismatic. I can see why you have so many subscribers. Gonna subscribe and see what other cool videos you have! Thanks!

[@DavidPozEnergy]

Thank you.

[@TheWickerShireProject]

Morning Dave! ( Ok watching ) We finally hit over 2k + watts 41 amps This morning. Been burning 1 gallon of gas for the last 4 days. Too cloudy this time of year. Worst month in TN

[@DavidPozEnergy]

1 gallon over 4 days is really good.

[@TheWickerShireProject]

@@DavidPozEnergy I should word that Better. 1 gallon of gas per day. 1/2 gallon at 7 pm and 1/2 gallon at 4 am. 4 gallon fuel @ 1 gallon a day to push us through till sun power. Crazy cloudy last 4 days. 3.1 Kw Hrs since the sun came up at 7am now almost 12 Our time. Hoping to make 7Kw Hrs today

[@DavidPozEnergy]

Still pretty awesome.

[@TheWickerShireProject]

@@DavidPozEnergy What do you think? I have 3 cracked Panels ( series ) not in use. Should I stick them on their own charge controller and add them to the system? Is it ok to have 2 charge controllers? This would be set to 56.2v vs the Outbacks 56.7v ( would you add the panels on to the array?

[@DavidPozEnergy]

I don't use cracked panels and don't think they are worth the time to try to make them work. yes, you can have multiple charge controllers feeding the same battery, but they would all have the same settings.

[@toneault7499]

hi david. sorry ive been a little bisy.. as per a great job.. and the hair and beard are looking good to hope to hear from you soon. tone UK

[@timburk6097]

I own 3 of the Mep831a. Gen sets and they are a bit finicky but I like them. The older ones have inverter failure issues as well. Prefer units with inverter serial numbers higher than 9000.

[@robjohnston8632]

Another great video! I hope you will try the diesel at 80% to see if it is more efficient and also include the difference in price per gal for gas and diesel in your calculations for the comparison.

[@icey_projects]

Agree would like to see $$per kwh diesel vs petrol, curious if it would be roughly the same price wise, also nice 831A have one myself as well as an 803A :)

[@proehm]

When I was working, both of our standby generators at both sites got a consistent 11kw per gallon. The smaller one used 22 gallons per hour and the larger one 27 to 35 depending on load. Your consumption seems pretty reasonable.

[@DavidPozEnergy]

Very cool. I appreciate you sharing some more data. Do you know any specs other specs on the generators?

[@TheBeardedDog]

Very interesting comparison. Where I am at diesel is a bit more expensive than unleaded, 30% more expensive. It would seem from a cost perspective it would be a wash. The plus side for the diesel generator though is it could probably run on just about anything that will burn.

[@1978jra]

I have never bothered to find out what quart is, now I know! It is quite close to 1 litre. One gallon is (or close enough) 4 litres.

[@TheDigitalMermaid]

I've been planning of getting a 1-cyl Yanmar to drive a Balmar 100A 48v (58v) LFP aware alternator... Figured it'd be the smallest package I can get and avoids the losses of AC -> DC conversion. If your numbers are not too far off what I'd get, then my 45 usg of diesel would give me 360kwh, or an additional 163 hours at ~4 knots, or 654 nautical miles of additional range, for a total of 827 nautical miles range, purely off the starting charge and what I could generate from the diesel. Holy crap!

[@corborst4872]

Aren't balmar alternators a ton of money, and while being an alternator, not very efficient, maybe 60~ish % Better find yourself a moped or bicycle hubmotor and try to run that off an engine, put the AC through some diodes to make DC and charge your battery like that, more efficient and cheaper. The more rpm you put into a permanent magnet hubmotor the more voltage comes out, once it hits battery voltage it comes under load and becomes harder to increase rpm, it is then charging the batteries. Most hub motors run quite cool at 2/3 of their rating, cool = efficient, so DavidPoz gets 21,5% efficiency out of his diesel Genny, I get about 28% out of a 36 year old diesel engine with hub motor, I bet a modern Yanmar would even be more fuel efficient.

[@hippie-io7225]

A gallon of diesel or gasoline is roughly 33KWHrs. So a better approximation of efficiency is KWhr produced by generator / 33KWHrs. You can do that for vehicles as well. My Geo get around 40 miles per gallon. 1 gallon approx = 33KWhrs. 33,000 WHrs divided by 40 means I use 825 Watt Hours to go 1 mile in my Geo. Electric cars use about 250 to 300 WHrs to go that same mile.

[@mcarling6495]

A gallon of diesel is 43.1 kWh. A gallon of gasoline is 36.6 kWh.

[@augustedionne9014]

Hi David, Upfront I want to say I love all your videos and thanks for producing them. I can tell you certainly love this stuff by the energy you put into your videos. It seems that most times you hit what the mfg. STC Standard Test Conditions results are listed at. At least that's what I've seen you do with Schneider equipment. As for me living off grid is gratifying in some ways but a lot more work than most people would think. I know everyone has their own opinion and some folks come from the mind set that Army Equipment is built better than any thing else. IMO all I can say is "run" when ever someone offers you something built for the military. While you and some others that run these have good luck I've heard more horror stories about people buying army surplus and having nothing but heart ache. Additionally military equipment as you stated is finicky. Saying that the army spec is conservative to me holds no water at all as everything ever designed by an engineer has a safety factor built in. Anyone running any equipment over loaded constantly is only asking for premature failure. Especially electrical equipment. For me an 1800rmp water cooled diesel generator can't be beat. Add a cheap engine controller to it and you can auto start it from any of your solar components that have a programmable Aux. output. So for you it would be just two wires back to the Schneider XW6848 or your 100/600 Mppt. Just for reference CentralMainediesel.com list the specs for a lot of diesel gensets. In those specs are gals consumption at 1/2, 3/4, and full load. Based on the printed specs a Kubota 9.8kw genny consumes 0.41 gals/hour or almost 12Kw/gal. That's twice the published 0.5gal/hour for the MEP831A genset. Also I was just curious why your are running such a small generator? With your current EG4 600ah battery bank and inverter charge setting of 300amps (1/2C) you would need 300 amps at approx 54 volts or 16.2kw to achieve this setting. Your generator is only a fraction of this capacity. Is your inverter surging the load to the genset when its running? I'd assume it would constantly back off and re-engage as the incoming voltage and hz from the generator dropped. If it is I'd recommend reducing the charge settings in the inverter to match your 3kw generator and adding a engine control module to it. That would make your goal of staring your generator based on SOC much easier to accomplish. Good luck with all your off grid goals and keep up the great work on your videos.

[@DavidPozEnergy]

I own several generators. I like working on them, fixing them up, and building them. I also own an 1800RPM liquid cooled diesel and it's also my favorite. I like the MEP831A for it's own reasons. 0.5C rate is the maximum recommended by EG4 for charging. However, the batteries can be charged at less C-rate. If I charge a 600Ah battery at 50A, that's under 0.1C rate, but it will still charge. I don't run my generators directly through my inverters. Instead, I use a "Chargeverter" (link in description). This way, the generator charges batteries, but the inverters power the loads. I have another video on testing the pass-through, and "generator support" functions in the Schneider: kzbin.info/www/bejne/aWerZ4aYZ656lc0si=pzBOiGOJS9YHh18K

[@bbariceo]

Great video. I found one of these generators on Market Place with an asking price of $1200, in running condition with very low hours. Unfortunately I didn't know what I was looking at and while doing some research it sold. I like the idea of using diesel fuel over gas because diesel stays stable much longer than gas and has more btu per gallon. That being said, if l'd of seen this video before I'd have that generator.

[@DavidPozEnergy]

I have a couple for sale in Massachusetts, but the ones I have are not running yet. I still have to go through them. Or, I have a friend in North Carolina that has some too.

[@bbariceo]

@DavidPozEnergy What part of North Carolina is your friend in? I live right near the border In Virginia.

[@DavidPozEnergy]

Contact information for Chris, if you want to buy a military generator: [e-mail]

[@tomstdenis]

Nitpick: Diesel is more energy dense than gasoline per volume. So you should convert all of them to Joules and then see how many Joules of fossil fuels per kWh of charge. For instance, 2.35 gal of diesel is about 318.4MJ of energy and you put 67.3 MJ into your battery or about 21.13% efficiency. Whereas a gallon of gas has 121.9MJ of energy and 5.9kWh is 21.24MJ of energy, an efficiency of 17.42%. So yes, the diesel is more efficient.

[@adistezar]

You could try to engine swap the alternator generator with a 168F diesel engine. That could get the efficiency higher, closer to the MEP and over the Honda.

[@operator8014]

There's one of these auctioning on ebay right now, local pickup only in Georgetown. Should be able to get a hell of a deal on it if you're local to that area.

[@inothome]

LOL, the shunt says "minus" instead of negative. High quality there.... lol

[@Sylvan_dB]

Diesel always has more energy per gallon than gasoline, because chemistry. I'm glad that generator was able to extract it. The simplicity of old diesel engines might make the aggravation of dealing with a second fuel source worthwhile (if you don't already keep diesel). I have a small diesel tractor, but I'm still not convinced a small diesel generator is for me. I think a 15kw or so PTO driven alternator for direct D.C. charging might be just the ticket if I can find one at a reasonable price. Until then probably a cheap (not Honda) inverter generator will have to do. So cheap, so obtainable. And so far plenty reliable for the price.

[@2point..0]

I would like the Military style generator, because its a beast and built tough!!! But I was lucky enough to get a Hoomy Depot Glitch a few month for $279.00 it a PULSAR4,500-Watt/3,700-Watt Dual Fuel with Recoil, Remote and Push Button Start Portable Inverter Generator with CO Alert and its much smaller and it hopefully use that much Propane... I have not started it yet!!! Liked#138 N Subscribed!!!

[@DavidPozEnergy]

Good deal. I hope it starts well for you.

[@bruceleonard81]

I used to have a semi and I had a rig master 4000 watt generator with a 3 cylinder diesel engine. This was an economical way to have a heater or a/c on the truck and have power to run a microwave and tv. Those little generators ran on like a quart of diesel an hour full out running. All I am saying is, you might find an older one cheap and check it out.

[@DavidPozEnergy]

Thanks for the tip. I'll see if any show up on the used market

[@mvansumeren4313]

If I did my math correctly, the diesel generator was just over %21.4 efficient and the gasoline Honda managed %17.5. Not bad for portable units!

[@biglog5112]

I find a couple of issues with your comparison: First, diesel has more energy than gasoline and costs 20% or higher more than gasoline. Second, the comparison of the Honda which is 5500 watts and the miltary is 3000 watts. I find that the larger the generator the more fuel it consumes at lower loads. So it would be better to compare another 3000 watt inverter generator to the military. On my 3000 watt Champion I usually could get around six hours on 1.5 gallons a gas using a 13,500 btu rooftop ac.

[@WimPrest]

Except it's not about comparing diesel to gas. It's about comparing multiple types of generators to each other. Fuel in. Electricity out. Everybody's choices are different. What's most important to you, fuel type? Maybe size? Maybe noise? What about price? There are way too many considerations to just pick one characteristic and die on that hill when you're helping a few hundred thousand people.

[@apex007]

Are you off grid yet? An update on how close you are would be nice. Would be good to know how much it cost too.

[@northidahodreaming5657]

Thanks for doing this. I'm off grid winter charging batteries with gasoline generators. I keep looking at diesel generators (new) which are many times more expensive than gasoline open frame units. I'd like to know the ins and out of locating a military diesel generator.

[@DavidPozEnergy]

Your welcome. There are a ton of options out there, it's nice fun to compare a few.

[@NeverTakeNoShortcuts]

I have a lot of generators. Nothing beats, however an 1800 RPM liquid cooled prime diesel generator. Both for longevity and for efficiency, as well as being much much quieter. These smaller generators in particularly the Honda gas generators have are standby generators, and not meant for prime use, so if you want to run these for days and days on end they will not last very long

[@erikj9962]

I would be interested in an effecency vs load test. For gas you want high load, but for diesel I think closer to 50% load is better.

[@CNCElectric1988]

hi, this is zoe from CNC Electric, how can we access to for details about cooperations, sir

[@affordabledcgenerators1607]

Very cool video 👍

[@jakealmaguenther4366]

I’ve been watching your channel for years, especially the generating projects. Have you ever considered using a brushed dc motor as a generator and connecting to the pv input on the inverter.?

[@DavidPozEnergy]

I did that with my treadmill project. The treadmill motor is brushed.

[@kennethalmond8922]

Good one. I must say I'm surprised at the (hi) 8kwh/gal! but of course, there's nothing like actual tests to get data :)

[@ndudman8]

so thats about 21% efficient :) as theirs 10 kwh energy in 1 litre of diesel ? which is what the internet tells ya if you search I think.

[@michim162]

Und hier der Grund warum: Sie sind traditionell 20 bis 30 Prozent sparsamer im Verbrauch, weil Diesel über eine höhere Energiedichte verfügt und Dieselmotoren das Luft-Kraftstoff-Gemisch wesentlich stärker verdichten. Diese bessere thermische Ausnutzung der Energie im Kraftstoff erhöht den Wirkungsgrad

[@K0nst4nt1n96]

You should find a way to scavange the exhaust heat to heat your home.

[@Pogeyjames]

Should try to make an alternator with an electric motor. Free energy

[@amsoiladam]

I really curious where you find the military diesel generator. I use a harbor freight predator 3500 with my RV. However, my RV is diesel powered and I would rather have something on board that I did not need a separate fuel supply for. I just want to tap into my 200 gallon fuel tanks. It’s very difficult to find a diesel generator. And I don’t need a really large one. Just something to charge batteries in the case that my off grid system doesn’t get enough sun.

[@sstreet9436]

I was curious on the actual cost per kWh, thus using @DavidPozEnergy 's measurements and the current fuel cost averages for North America. Both the MP-831A and the Honda generators will cost about $0.53 per kWh. Not surprising they are the same as they both are producing the same amount of work in the end. What is the real difference is run time between refueling (the larger military gen's tank runs like 8hrs at rated loads, while the Honda will probably run 5hrs at the same load). Additionally, you need to factor in maintenance and repairs; the diesel engine requires more expensive maintenance parts (oil, oil filters, fuel filters, etc), while the gasoline engines have much less expensive (and perhaps more readily available) maintenance items and repair parts. Though, admittedly; running surplus military equipment does up the "cool" factor and keeps a piece of perfectly good, over-built, equipment from the landfill/crusher. Thank you David for your continued experiments and observations; look forward to the next video.

[@alexsimmons1803]

Nice test. By volume automotive diesel is ~15% more energy dense than gasoline/petrol, so that accounts for about half of the "efficiency" you are reporting. Your numbers are really "economy" values than efficiency (similar to mpg used for cars). Efficiency (as you know) measures the ratio of energy out to energy in, and for that you need to use the specific volumetric energy density of the fuel used. So I'd say the military generator is ~15-20% more efficient than the Honda, but has 35% higher fuel economy. No idea what your diesel vs gasoline prices are like there. Here (Australia) diesel is typically 10-15% more expensive, although it can vary. All our petroleum is imported. I'm just about finished with the need for using a generator as a backup charger for our off-grid system. Rarely use it anyway. We have a battery electric vehicle now and the vehicle to load (V2L) function will enable me to put a steady 2kW into the battery via a spare AC to DC charge controller I have (a spare all in one inverter) - using it like just the Chargeverter you have (Chargeverter is a bit more convenient but functionally I can set the charge voltage and current in 10A increments, so 40 A ~ 2kW. With some tweaking I think I can up the V2L 3kW but 2kW is ample for that steady supplemental recharge, even 1kW or 1.5kW would be plenty for us. Our Winter PV production will be much better than yours, our latitude is ~ 30.5° from equator (south). The EV can comfortable supply a spare 35 kWh (given it's typically sitting at ~ 80% SOC), and with planning it can be closer to 45 kWh available while still having ample capacity for local driving or to reach a DC charger in another district. Normally it is charged from our grid-tied PV array but I can slow charge from off-grid if needed (especially when I add the extra off-grid PV this year).

[@DavidPozEnergy]

Thank you.

[@greg227]

Love the video, convinced this is one thing I need here living off-grid. One thing I wonder is if I could use black diesel with it?. However, there seems to be a flaw in the way you did the test. I would have done the test differently for more accurate results. I first would have measured out the diesel into a portable tank. Then I would have put a fuel line from the fuel pump inlet to the tank inside the unit. This would allow a more accurate measurement of consumption. It would not have mattered if it was 2 gallons or 10, the numbers would have been the same in the end.

[@DavidPozEnergy]

There are several ways to get there. I admit that there is some margin of error in my method. My goal is to get the big picture between the different generators I have available.

[@raymondfrank9202]

good one

[@mannfamilyMI]

Great video David! Could you let us know what happened to your yellow SMA inverters? I’ve been looking through all of your videos but I can find any mention once you switched to grow watt.

[@DavidPozEnergy]

I sold the SMA in order to afford the Schneider.

[@rayherriott6517]

One factor which affects an efficiency comparison in terms of fuel consumption is the fuel itself. Diesel has approx. 137,000 BTU/Gal and gasoline has approx 125,000 BTU/Gal

[@D2O2]

When you compare $ of fuel/kwh, the diesel generator is only 2% cheaper per kwh based on fuel prices in my area compared to the gas Honda.

[@WimPrest]

That is only true today. The cost and the ratio between them changes all the time. This is more a comparison and exposure to different types of generators so that people can make an informed buying choice.

[@joehomer4421]

Please keep the area around fuel fill neck clean and free of debris. Contaminated fuel is a big problem with diesel engines.

[@arturmarcio630]

nice but not so precise efficiency comparison, you can't compare gasoline with diesel using only volume parameter, it's much more complex, but thanks for the video, it's great! I would like to know about thermal integration, using the heat from generator to warm water or something else, greetings from Brazil!

[@av1204]

I used my tractor pto generator and can get pretty good kwh per gallon. I tried measuring it once and think it was a little under 10.

[@rongray4118]

I am looking into the same platform for a Unimog 406 pto driven generator. I am interested in hearing what kind of battery system you are charging. We are going off grid 48 volt system.

[@vmoutsop]

Quick search shows these are listed between 2000-$3000, so $1k at auction seems like an exceptional price.

[@DavidPozEnergy]

That's because when I bought mine, it wasn't running.

[@vmoutsop]

@@DavidPozEnergy ah yes, you did mention that. My bad.

[@ThePaulv12]

Beware however, The engine life for making rated power tops out at around 3000hrs. I've got one and one engine expired before 500hrs, the second brand new engine now can't make rated power at 3500hrs on the hour meter. It makes only about 75% of rated. No governor adjustment makes any difference. It's still useful as a backup. Always had regular oil changes.

[@TrackGeeks]

@@ThePaulv12 Have you pulled the fuel injector? They have a service life of 1,500 hrs on that engine. Any oil consumption?

[@joecummings1260]

Those automotive alternators are not very efficient, and they need to spin like 6000 RPM for full output. I wonder how a brushed dc generator would do. You can find a lot of lower voltage DC motors in old forklifts and pallet jacks. You want to find one with a shunt field. They work perfectly as generators. What is the voltage of your storage batteries?

[@mattharvey8712]

Bravo.......u can run propane good for cold......mix.......both......or.....diesel only.......bio fuel stuff.....cheers

[@drewcress]

Sorry to be 'that guy' but there is about 12% more BTUs in diesel than gasoline, so comparing them on a per-gallon basis will not accurately convey efficiency. On a BTU per watts basis, this places the Military generator at 5.8 and the Honda at roughly 5. That is a difference of 14% in favor of the Military generator once the fuel difference is accounted for. A more accurate number, but not a partially important one. The 35% number originally given is actually much more useful to determine run cost .... you just have to include the cost difference of the fuel. Let's assume you are running regular in the Honda. Ballparking AAA numbers for the USA gives us a very rough ~$3 for gas and somewhere between ~$3.75 to $4 for diesel. The break even point (with gas at $3) is $4.05 so the question of which is cheaper to run may very well come down to the cost of the fuels where you are at and on that particular day. Given these very general prices, diesel does still come out ahead, but it is 1 to 10% cheaper to run as a rule of thumb. I'm sure the above rings a bit more accurate deep down, but I also know '35% more efficient' sounds really nice to someone who just put a good chunk of time and money into the project! It happens to us all. If you want to go a bit dipper into this, you might want to convert the DIY version to propane for further comparison. Propane has the advantage of not going bad in the tank and fouling out when you most need the standby power. It also doesn't need the extra heat (usually via electric) to start up in the cold that a bigger diesel does. To dive off the deep in, start making your own biogas (methane) via anaerobic composting. Could be some fun videos!

[@WimPrest]

Hey "that guy" while everything you said might be mathematically accurate, the video is just fine. He compares a generator to another generator. He didn't get it wrong. He gave people a starting place to be able to make an informed decision about buying a generator based on what's most important to them. Your fuel cost estimates are only valid for this week they were wildly different 3 years ago and different 3 years before that. Most people buy a generator and hang on to it for a very long time so relative fuel costs at a point in time are completely irrelevant

[@realvanman1]

That works out to just about 20% efficient, fuel energy to DC to the battery. Pretty low for a diesel, but there were the extra conversion steps. An engine direct driving a good 50 volt DC generator (not just an automotive “alternator”) would be a better way to go. Regardless, it exemplifies why off grid generator sets should always focus on heat recovery, as that’s where most of the fuel ends up. The electricity generated is but a small fraction of the total energy purchased in the fuel.

[@paillart527]

Hi David. Thanks for your videos. So, the result is 8Kwh/gal so in metric 2.1Kwh/liter. One liter of fuel is 10Kwh energy. So this old army generator has an overall efficiency by 21%. Sound like low. Maybe with modern ICE it would be better but not proved by the Honda result....surprising! Anyway finally, the generator can provide 24Kwh with a tank full and it is the most important to know in case of emergency.

[@DavidPozEnergy]

Not exactly. Remember, I'm measuring the energy being put into the battery bank. All the electricity is going through the charger (yellow box on floor). The charger is about 90% efficient.

[@paillart527]

@@DavidPozEnergy : Yep I forgot the charger. So, efficiency raises to roughly at 23,4%. Thanks for the note. Regards.

[@annaplojharova1400]

Inverter generator is not that much efficient at full load, the main point of that complexity is the efficiency (so fuel consumption) mainly at partial or mainly light load, something you will get from rather normal home when no batteries are involved. The point of the inverter is to allow to operate the engine at rpm most optimal for the given load, so gain mainly at light load, when it uses to spend most of the time (without batteries). Having batteries indeed allows to operate the generator at its peak efficiency all the time it is running, but then you won't need the inverter complexity and related losses in it anymore. Your comparison mainly shows differences between energy density in fuels and general efficiency difference between diesel vs gasoline engines.

[@mcarling6495]

The other point of an inverter generator is a much cleaner sine wave (less harmonic distortion).

[@victorcarreras2499]

Good generator,i just to fix those in the army

[@ChatterontheWire]

military = diesel, civilian = gas, what is the difference on cost in your area between fuel types?

[@corborst4872]

That is about 21,5% efficiënt, there is 37.1 kWh in one gallon of diesel fuel. I made myself a permanent magnet battery charger from a hubmotor and a 36 yo Hatz 1 cylinder diesel engine, I run this to charge my 48 volt battery bank directly without inverters or electronics, I only run the AC output through some diodes to get DC for the battery, this increases the efficiency even more, i calculated mine at 28%

[@jontscott]

How much of the efficiency gain do you think is diesel vs gasoline?

[@TheWickerShireProject]

Diesel fuel is said to have between 10% to 15% more power as a fuel source. Vehicle engines are said to have a 25 to 30% gain. Dave shows the comparison in this comprehensive video. Diesel wins!

[@jontscott]

@@TheWickerShireProject So how close could the DIY generator get if it was diesel? 4.85kw +30% gives maybe 6.3kw... I guess the military generator still wins.

[@Zorlig]

​@@jontscott the military one looks to have efficiency in line with a larger higher end propane generator. Either way, the problem with it is that it's so small that you'd rack up the hours quickly when you needed it. Get yourself a 30 kwh propane generator and you'll have the best performance, no refilling the tank and only gave to run it for an hour a day to fill the battery rather than 10.

[@genegardner5060]

Something important to remember is that diesel could be about 20-35% more efficient per gallon than gas since its energy density is higher and burning characteristics are better for efficiency so that may be the reason its testing more efficiently than the gas generator. A better comparison would be cost per Kwh since you need to take into account the added cost of diesel over gas. so in reality the honda might cost you less per Kwh if you calculate in cost per gallon.

[@patrickday4206]

If you ever need to buy another generator buy a military welder it will already have dc around 48 volts at about 200amps your mppt charge controller can handle them my old one could do 500 amps with adjustable amperage dial with a very efficient perkins deisel i payed 1100 for it

[@DavidPozEnergy]

Thanks for the tip

[@MrButuz]

Good vid - most of that 35% is likely just deezil v gas difference. It would be interesting to test the military gen against a commodity deezil gen like one of those hyundi 5kw deezil gensets??

[@USA-GreedyMenOfNoIntegrity]

If you buy enough solar panels and batteries, you will rarely need a generator. Off grid for nearly two years. Less than 25 hrs on the LP powered 10kW Generac. Most time contributed to monthly testing.

[@offgridwanabe]

Up here in Ontario Canada that is still close to 1 dollar per kwh which is great for an emergency

[@D2O2]

Only 43 cents USD where I live in the US.

[@DAH-ss1nu]

I would have liked to see a efficiency comparison calculating the two different fuels: how much potential power in the volume of diesel used vs delivered energy compared to how much potential power in the volume of the gasoline used vs delivered energy. That would have given a true apples-to-apples efficiency comparison. Then you could have gone into cost per KWH into the battery bank. Would have presented a much more nuanced picture and made for a useful video.

[@WimPrest]

Those might be technically interesting, but it doesn't really change what matters: how much electricity can I get out of a gallon of fuel? A person may not have diesel readily available, or the space for a diesel generator. This is all about finding the best possible machine for your individual use case

[@charlesdavis8250]

David, have you ever thought about using a small 48-volt wind turbine? By the way your channel is sweet... great information

[@DavidPozEnergy]

I think it would be fun to try a cheap wind turbine. However, my location is terrible for wind. Low average wind speed. I don't have enough room to set up a large tower. Lots of trees on neighbors property.

[@charlesdavis8250]

@DavidPozEnergy My set up has similar issues. When I get everything assembled on my new building I would like to try one on the roof of my shop. Living in South Dakota the winter is short days. Love all the information you have provided on your channel!!

[@charlesdavis8250]

@@DavidPozEnergy Have you picked out a wind turbine? I have not found one that I was impressed with.

[@DavidPozEnergy]

No, I have not picked out a turbine. I would need a very low-speed start-up.

[@JGnLAU8OAWF6]

I wonder how (in-)efficient is charging from alternator of idling car compared to real generators.

[@casemodder89]

i also like that question. the problem is: cars in idle turn the alternator at like 1500-2000 rpm. and thatvis the lowest end of producing current at all. so a 100A alt would put out like 28A in idle. at 14V. that is Nu-Thin if you need to run a homestead off that.

[@manoo422]

This works out to be a total efficiency of 21% which is really not a very good return on the cost of fuel. Perhaps a more 'combined heat and power' strategy would be worth considering for off grid use. Nearly all of the 79% was heat...70kWh of it. That would heat a metric ton of water from 10 to 70 deg C.

[@joeerskine3920]

Mep-952b is 28 volt dc 5 kw. Even more efficient and simple. Don't know if there's a 48 volt model.

[@lunatik9696]

I have the Westinghouse i2200 (1700W; 1.3 gal) and i4500 (3700W; 3.4 gal). I have EG4 24V charger (900W/ ~1250W) and a Victron (300W/ ~450W) The chargers have a pF = ~0.7 ! (output/ input) Generator output = charger input. 450+1250 = ~1700W input so it is right at max running power. The i2200 is more efficient running full load. I get about 4.5 to 5/5 hours at full load. EG4 + Victron It will run close to 12 hours running just the Victron. (overnight) The i4500 has more capacity and a longer runtime. It will run all night connected to 1 EG4 charger. The i2200 can run (01) EG4 24V 30A charger AND a Victron Blue 24V 12A smart charger. The i4500 can run (02) EG4 24V 30A charger AND a Victron Blue 24V 12A smart charger. I think the smaller engine has less friction, etc so the fuel not used directly for charging is less.

[@AntoineGrondin]

It would be awesome if you can do the same experiment with the Honda EU3200 which is rated for the same continuous load. I would love to know its kWh/liter rating.

[@DavidPozEnergy]

Yeah, that would be a good comparison. I've never tested the EU3200. However, I have tested the smaller EU2200 model in a past video: kzbin.info/www/bejne/h3LSoKWcmceYnNEsi=VcdNABj1cQaecr08 That might give you some idea.

[@AntoineGrondin]

@@DavidPozEnergy yeah but the 2200 is carburated and with an older engine, not the new direct fuel injection engine. I assume the fuel efficiency in terms of kWh/kg or kWh/liter will be better, but I'm not sure how much. There's basically no one looking at the fuel efficiency like this, it's pretty annoying. Aside from you, that is! Although another idea for you: these engines are most efficient at different load %. Maybe try to find how they perform at various % load? I.e. if a diesel genset is rated 5kW, compute the fuel efficiency at 1kW, 2kW, 3kW, 4kW, 5kW. I believe there's large differences.

[@DavidPozEnergy]

I agree that it's pretty annoying that this type of real-world fuel testing is not being shown. I'm trying to change that with what I have available. I'm always willing to test more generators if anyone is around me and willing to loan me theirs. I made a video comparing different % on my Honda: kzbin.info/www/bejne/oYK3d4ODeaqSfJYsi=9_q4Ks81ErQ45fh0

[@renoflames]

How many dollars per hour to operate the Army Generator. How many gallons per 24 hour period. Just curious.

[@DavidPozEnergy]

Hmm... Not sure. I've never ran it for 24 hours straight. I use it to supplement my off grid solar system at times I don't have enough solar energy. The most I've ran it is 8 hours straight. Just did a little math. If I ran it for 24 hours, it would consume 9.4 gallons of fuel. The going rate is about $4/gal right now for diesel in my area, which is $37.60/day.

[@KD2HJP]

I say this nearly every year to you, but I am available for adoption or even short term rental..

[@TheWickerShireProject]

He's like a brother. Dave is an Amazing person! One of those Gems you get to meet if lucky. Always bring a notebook.

[@MrTonyPiscatelle]

I have a 7500 Generac that only consumes a gallon of gas per hour under load. 100% load ? no I never operate it at 100% but 75 to 80% yes. The fuel being gas is less expensive that diesel as well. My Generac will go a whole shift as you said civilian generators won't do. Not to mention it makes a ton more power than the one you showed in the video and also to boot has a smaller foot print.

[@AH-li7ef]

Here in Finland, diesel and gasoline are roughly the same price, approx. 1.8€/l, tax-free diesel approx. 1.4€/l (11.8kwh/l). I heat with "free" wood 4kwh/kg, my electricity usage is low, I just received the electricity bill for the end of the year 143kwh/2 months energy price 1.3€😂 I have a stock exchange electricity contract, (electricity is priced hourly) and the Norwegian electricity seller made a mistake and the price of electricity for 9 hours was -0.5€/kwh, normally 0-0.3€/kwh, they had to pay to me use electricity during those hours. The monthly payment for the electricity contract is also €5/month and the very expensive electricity transfer fee is €40/month +€0.07/kwh. In ten years, almost €5,000 will be spent on fixed payments, which would probably get some kind of solar power system, but there are at least three major obstacles to that, November, December and January😢 I guess that 15% is still lost when converting from the batteries back to mains electricity?

[@580guru]

@DavidPoz Missing your videos. Hope you and family are doing well❤

[@DavidPozEnergy]

Thanks

[@flotsamike]

Diesel has about 10% more energy in it per gallon than gasoline. Some sources say it's 15% more energy dense. Still the diesel generator is ~25-30% more efficient.

[@MrGots2sail]

FYI the "Battle Short" switch will defeat the built in safeties.

[@DavidPozEnergy]

Everything except the low-fuel shutoff.

[@chrisloving6647]

Can you bypass the inverter in the gen and just use the 3000w straight in to a charge controller? I feel like all the heat lost in the inverter and yellow charger is at least a kw.

[@DavidPozEnergy]

I'm working on it. It's far more complicated then it appears on the surface. But, I'm recording myself as I work through the issues. At some point I'll have a video on it.

[@kchiem]

Not really a direct comparison with the Honda since they're using different fuels.

[@WimPrest]

It really is a direct comparison. Generator versus generator. If fuel is critical to you as a consumer, you make that choice

[@CdoGtheGreat]

How about anther calculation with fuel cost. Diesel typically costs more than gas. Also some of the Honda generators are multi fuel. You could expand on that as well. Propane, natural gas, and gasoline. I bet your military unit is still the cheapest to run but it might be a little closer.

[@DavidPozEnergy]

Thanks for the comment. You are correct, that because diesel is more expensive, there is very little cost savings between my Honda and this. The Honda has been great, and is a good choice for plenty of people.

[@PaulHigginbothamSr]

David: On a diesel genset if ya'll turbocharge ya'll will lower the amount by nearly 1/2. But that would be at around 20lbs boost.

[@DavidPozEnergy]

I'd love to try adding a turbo. Any suggestions for a small enough one for this little engine?

[@beachboardfan9544]

Forget the genny, what are you doing to make your hair look so good!?!

[@niktak1114]

He runs a bit of diesel through it in the morning

[@schwinnminibike]

I would assert that the improved fuel economy of the military generator has everything to do with the improved fuel ability ... diesel vs gasoline. 35% sounds about right in the difference without doing the calculation. .. good video David .... good stuff!

[@chrislewis9345]

Hey David quick question... I have eg4 3000 at my cabin and getting shocked if I touch metal appliances and tools I'm using from it. It's worse if I'm wet.... aka concrete mixer lol. It's not earth grounded nor is any part of this temporary setup. It has a place for it on the chasis so I'm wondering if that's the issue? I haven't experienced this with my growatt 5000 at my house and they are not grounded but the house has the original ground from the main load panel. Any thots??thanks

[@DavidPozEnergy]

Grounding is never a bad thing, and I recommend grounding if possible. Note, I've never tested the EG43000 inverter, so I can't speak to that model. In general, if I was to get shocked by an inverter, I'd first check that all my connections look good. I'd check there are no loose wires, or fine strands of copper, that might be making a short to the housing. If I can't find something like that, then I'd either scrap the inverter, or if it's under warranty, get a refund.

[@buixote]

I like whisperwatt generators, cause they're so quiet... The Chargeverter must be connected in the correct "polarity"... I'm running mine through an Intermatic timer... Initially it would deliver no current. In reversed the brown & blue wires and voilá! Signature had no explanation...:-(

[@norsk54472]

what? you mean swap L1 and L2 - again what?

[@Subgunman]

Forgot to ask, I know of several generators like this but they have a tag on the outside marked "DE MILLED". ANY IDEA as to how Uncle Sam demils these units?

[@dryice-tech]

Hey D, diesel has more power than gas, perhaps better comparing prices per KWh instead

[@WimPrest]

Who cares which fuel has the most energy? This is comparing generators