What Size Inverter for a Microwave?

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Not sure what size inverter you need for your microwave? In this video, I'll walk you through everything you need to know to make sure you're sizing your inverter correctly, whether you're setting up in an RV, off-grid, or just want to understand your microwave’s power demands better.
We'll start by breaking down the power ratings on your microwave. I'll show you how to interpret the numbers you see on the label and what they really mean. I'll even test my own microwave to reveal its true power consumption-spoiler alert: it’s not always what the label says! This test will give you a clear idea of why you should always estimate your inverter needs at nearly double the microwave's advertised power.
Next, we'll explore the common misconception that using a lower power setting can help you get away with a smaller inverter. I'll test this theory by running my microwave on a low setting and showing you why it still pulls the same amount of power. If you're considering an inverter microwave, I’ll explain how these differ and whether they could be a better option for your setup.
Surge power is a major factor for many appliances, but not microwaves. I’ll break down why you don’t need to worry about surge power with microwaves and how my 2,000-watt inverter handles everything, even without surge capacity.
Then, we’ll dive into battery sizing and wiring. I'll show you the exact setup I use, including how to calculate the required battery size and how to wire everything safely. I’ll walk you through two detailed diagrams, covering wire and fuse sizes, so you can confidently set up your system. Whether you're using a single battery or planning a larger setup, I’ll explain how to calculate the amperage, choose the right cables, and size your fuses properly.
Finally, I’ll wrap things up by discussing the importance of using the correct insulation temperature for your cables and when you might need to double up on cables to handle higher current loads. I’ll also touch on NEC regulations and why they matter for your setup.

[@frans_d7989]

I bought a cheap microwave for AU$49 (about us$30) for camping. It has an efficiency of 58%. Better quality microwave ovens are about 65%. That is it draws 1200watts and has an output of 700watt. The problem is I had was that in the campervan I have has a Victron 1200W/24V inverter which will run the microwave at most for about 30 seconds before closing down. I tried a couple of different method to reduce the power, 1st being reducing the magnetron heater voltage which proved to be too unstable. Next was to use a PWM is a triac. This also proved to be too unstable. The last method worked well, that is using a variac and that worked. By dropping the voltage to 206V I am drawing about 900W which is fine for cooking continuously on my Victron 1200W/24V inverter and down to 400w at 190V. Maybe an inverter microwave is the way to go but no one makes a 20 litre or less sized microwave or get a bigger inverter

[@cleversolarpower]

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[@murraymadness4674]

If you are going to run a microwave from battery, you should get an inverter microwave, it does not use a big transformer, but has a dc-dc converter that converts AC into DC and the boosts the DC to 2000v. It has adjustable power levels, so it can consume much less power. and it also weighs much less, good for a camper.

[@cleversolarpower]

Indeed.

[@johndoe-eg7le]

I think you are the only one that shows the actual numbers and calculations !

[@carlosesquivel1314]

you are the he best I’ve seen so far got a question. I have a Toyota Prius I got an extra 12 v battery I want to use microwave and electric grill what size of inverter do I need the spare battery is 572 crank I’ll be connecting that battery to the existing car battery with fuse and cables and cut off switches

[@owolabiadeteye5919]

Great job, thanks for uploading this great lecture.

[@bothecat1966]

Thank you, what a brilliant video, I actually understood all of that.

[@cleversolarpower]

Great!

[@RichardBarleyphoto]

Thank you for the video, your videos are in depth. I am a bit confused should that mega fuse be a class T fuse

[@curioussand1339]

When choosing cables I somehow feel that when using the higher temperature rated cables at 105 degrees, you are designing a system with a higher than desirable voltage drop than necessary. The smaller cable dimension, which the higher temperature rating allows, also leads to a higher voltage drop. Sometimes it could maybe be desirable to go for the bigger cables with a smaller temperature rating but lower voltage drop? The price difference is maybe not too big, but of cause it's more cable and cable weight added.

[@cleversolarpower]

You can use a voltage drop calculator (or check my video). But if the length is not long, this doesn't really matter.

[@danielrodding8522]

The inverter needs to be so highly dimensioned that sufficient reactive power can be supplied. Here in Germany, transformers, inverters and such things are specified in VA (volt-ampere), and not in Watts. While the rating in Watt means it is for the used (or typically usable) current, the VA ratings include reactive power.

[@paraguard60]

Great info! Thanks for the upload.

[@Mmmmmmmiwish]

lov all the video's.. you give out great info for us all... can i ask a question .. if i hav a 3000w heater 220-240 v how much would it use in 2mins.. so 3000/60*2=100w then 100w/240v=0.416amps

[@benedalati1527]

At the minute 3:43 you used 1360 Watt in calculation. Is this the wattage rating of the microwave? Thanks

[@cleversolarpower]

Yes, this is the amount of power it draws when running it on 800W.

[@evensilset5522]

So there is no chance that a cheap 700w microwave will run of a victron 1200va 12v inverter??😢

[@BaderB-l9g]

Great info! I appreciate thank you.

[@jimbaggett1233]

Hi Nick, do you explain how you set up or the parts you use in your AC side power meter? Since most inverter wattage display meters are inaccurate I think a lot of people would like to set up something accurate like your setup. I've watched a lot of your videos and I apologize if you did cover this previously and I missed it, just point me to the correct video.

[@cleversolarpower]

The AC meter is this one: amzn.to/4cWsPpu

[@jimbaggett1233]

@@cleversolarpower Thank Nick!

[@trevortrevortsr2]

I have a 900watt Microwave and run it off my 1.5KW (3kw) peak soft start full sinewave inverter - it draws 93amp when the microwave is on full about 1200watts - my BMS is rated at 120a continuous my battery is 310ah lithium - we have one item on at a time rule in our RV for all big consumers like kettle, toaster and coffee maker - items like lights, TV and water pump run direct from the 12v

[@cleversolarpower]

That sounds about right.

[@ilanozana9652]

Generally the rate off power of equipment is power out .not power in.wich is p out times efficency.

[@retrozmachine1189]

Most ovens have the RF power and the actual draw from the outlet listed on the label.

[@cleversolarpower]

As you saw in the video it wasn't correct. 1150W was listed and it pulled 1400W.

[@retrozmachine1189]

@@cleversolarpower Panasonic NN-ST342W 800W RF (IEC-60705) 1270W, measured 1290W/0.99PF with professional equipment, 1300W with amateur equipment.

[@curioussand1339]

I understand the idea behind using two smaller cables instead of one big, but what happens if for some reason one of the cables is shorted to ground, then that one cable will draw almost double it's capacity (worst case) until the fuse blows. Question is if it can be guaranteed that the cable will not catch fire before the fuse blows. I assume likely the fuse will blow before enough heat has built up? But an even worse scenario would be if the second cable is somehow cut / disconnected without shorting, leaving the remaining cable with the task of carrying all the current. In this case the fuse will not blow and the remaining cable will overheat and eventually lead to a fire. But maybe that scenario is far fetched and will never happen (or has never happened) in real life? Likely the NEC rule ensures that the double cables are of a minimum dimension that will minimize the likelihood of an accidental fatal cut / disconnection.

[@cleversolarpower]

You need to fuse every cable. So if you have two parallel cables, you need two fuses. You can only split the cables up if they will be larger than 1/0 (55mm²).

[@ianjaeger4178]

im welding on my 3.6 kva 24 v off solar wind power here in the jungle west africa mig and arc

[@esmailalkassir1565]

Is wiring 2* 1,5 wires instead of bigger wire for 4000 W can cause issues?

[@namelesswarrior4760]

What do I need to run grow lights for 2-3 plants for 18hrs daily please?

[@jimsmith7212]

I just found your channel. (Algorithmic) Thank you and subscribed!

[@cleversolarpower]

Welcome aboard!

[@kennethchance431]

Hi thank you for sharing your video can you assist me with this I have a 24v/5,000W inverter I want to used it for my kitchen appliances also TV/washing machine etc what size cable / Fuse ? do I have to used Thanks in Advance.

[@jimmy_Ross]

dam thanks for sharing love to see videos like this

[@cleversolarpower]

Glad you liked it!

[@buggyduggy2431]

How about doing this using your car and the inverter set up. What size inverter can a car run?What is needed for a 1000w coffee maker? Can a car power a microwave. I want cheap & easy. Mostly I want to be able to make coffee in the morning when the power is out. Being able to run the micro for a few minutes would be nice too.

[@cleversolarpower]

Car batteries are not made for inverters. The batteries won't last long because they are designed to deliver high current for a short amount of time. Not to run loads. Check my video: how many batteries for a 1000W inverter.

[@benedalati1527]

How did you get 1360 watt? Thanks

[@cleversolarpower]

Thats what the microwave draws from the socket when i use the 800W mode on the microwave.

[@kevinswinyer3176]

I have a few questions. I live in a Vintage Class C Motorhome, that has a Microwave Oven, and there is a Converter in the Coach for a 30 Amp Service, but because of where I am parked on the property, my power Cable is not long enough to reach the power supply back at the main house, so I have purchased a 2000 watt inverter, and I am planning on having a battery bank of 4 12 Volt Deep Cycle Lead Acid Marine Batteries, hooked together in Parallel with each other, and eventually Solar. My Question is will my 2,000 watt inverter be large enough to power the RV Microwave, or will I need a larger inverter ?

[@cleversolarpower]

Depends on the power consumption of your microwave. Check the back for it's two power rating as shown in the video. I recommend getting lithium batteries. No need to wire in parallel and it will be cheaper. Check my recommended 12V 200ah lithium battery in the description.

[@kevinswinyer3176]

@@cleversolarpower I have checked the cost of lithium, and for me, it's cheaper to go with Lead Acid Batteries at this Stage of the game.

[@d.rayowens422]

Lithium has really come down in price to near the lead acid. They also give true output, you need half the amount. Also, last much linger with less degredation. You may want to do some research. Lead acid makes no sense currently​@kevinswinyer3176

[@NickSharpe]

@@kevinswinyer3176 you might have to rethink your cost benefit ratio. 4 FLAs? thats nutz! and so not necessary. Dont know where you been shopping , but a good 200 AH LFP is about 400 US and each of your FLA have to be over 100 ea. Study more to find the actual cost benefit

[@mikenagy938]

Nevermind the inverter, just make sure the microwave is on it's own circuit or you will blow the breaker every time. Also, they use a ton of power, so be ready to charge up your batteries.

[@louf7178]

What do gas dryer ignitors draw? I think it's hot surface type. I have a gas dryer that overloaded my 2000 W(3000 W peak) inverter. Thx.

[@cleversolarpower]

I don't have one so i really don't know. Maybe you can check the manual, it's should be in there. If it's a high frequency inverter, it doesn't have a peak surge even though it says so.

[@viyusavery248]

What about if the microwave itself is an inverter type??

[@cleversolarpower]

Inverter type microwaves are better as they don't have a surge power. If you set the microwave to 400W of power, than the microwave will draw 400W.

[@viyusavery248]

@cleversolarpower ok thanks, can I ask one other question I'm trying to make my own DIY solar system but I'm confused as to why some persons uses these dedicated bus bar strips Vs others not why should bus bars be considered or not

[@glennj6465]

Iv got a 650 x12v truck micro with 1000w renogy pure sign inverter with a 300 amp lithium batteries all with 35mm cables ( only less than 1m lengths )

[@sunny3560-e6y]

Out of curiosity, does anyone know why the actual power draw is such higher than the rated power? I recently found same issue on a new microwave, rated input is 1250w, output is 1000w, however the power draw is actually about 1600w.

[@ConciergeMed]

Hi. Can you help me please. I have a motorhome professionally fitted out with electrics. This allows me to charge both the starter battery and leisure battery when hooked up to mains electricity. (I do not have solar panels or use lithium batteries) My question is, can i hook up to mains electricity to charge my leisure battery as above but at the same time, plug in my portable 2400W power station inside my motorhome socket to charge it up when the mains hook up is still connected? Hope you can help, thank you.

[@cleversolarpower]

Yes, it will be a little more inefficient, but will work. Because: AC (mains)->DC (battery charger)->AC (inverter)-DC(battery charger) instead of AC(mains)->DC(battery charger)

[@ConciergeMed]

@@cleversolarpower Thank you!

[@jimnunya1253]

Where the information come from that says we shouldn't double up wires under zero gauge or whatever? 1 + 1 = 2 2 + 2 = 4 8 + 8 = 16 I don't see how the math breaks down to any sort of an unsafe level. I'd say it depends on what you're using the wires for and how much juice is going through there and if you need a bigger wire add more wire as long as the numbers match in the end. I typically will run doubled-up or even quadrupled-up 12 gauge copper wire for my stereo amplifier to speaker and it works great at no additional costs of specialized sizes with specialized prices. As long as your lengths are fairly even and the total mass of cables becomes equal to the wire gauge needed, all is good. Maybe it doesn't look quite as neat but the electrical flow will be nearly identical as well as heat generated in the cable. I braid mine. I believe the cable jackets are actually cooler on a braid than a single mass wire with thin skin jacket, especially when airflow is present. You're single fat cable can build up heat and actually trap it and it will continue to build up as you run power through that wire. Cooler wires transport electricity more efficiently than hotter wires.

[@cleversolarpower]

It's in the nec (national electric code) handbook.

[@muhammadshafiq6634]

Dear, i appreciate your's efforts. I am from pakistan, can you guide how many books are you written and how can i get these books in pakistan, and i do not have any bank account. Please send me your entire books name. Thank you so much.

[@cleversolarpower]

You can get it on my website as well.

[@FreedomFrederick-p9x]

Many electrical and electronic products have a very high start up surge current that lasts for a microsecond and more ..this is almost never on the label about power use ..

[@cleversolarpower]

Indeed.

[@LindsayHindle-v9f]

When you are calculating amps based on 90% inverter loss shouldn't you multiply the 166 amps by 0.9 rather than divide.

[@cleversolarpower]

No, to take the efficiency factor in mind you have to divide. Otherwise you will end up with a current lower than 166A, while in fact it needs to be higher. Input power of inverter is greater than output power, hence 90% efficiency.

[@curtchase3730]

So, an inverter microwave will actually run with reduced output power when you dial down the power? I know standard units just pulse on and off from full power to zero and back. I hate that. The only microwave oven we had that tried hard to overcome that on/off cycling was our old Amana beast from the 1970's. It had a really cool duty cycle where it really pulsed the power, not like the modern junk units do. Example, set power to 50% on the old Amana and would actually cycle the magnatron ON for 1 second, off for 1 second! The food could heat without boiling and sputtering as much. I would love a microwave that actually REDUCED the output power without that stupid pulse on/off stuff.

[@cleversolarpower]

Yes, inverter microwaves keep their input power the same. There are some video's online showing it. Normal microwaves turn on and off.

[@retrozmachine1189]

Inverter microwaves do actually cycle the magnetron on and off since that's more or less the only way to control themr but they do it at a much much higher rate than the old heavy transformer types. Add in the design of the AC > DC in the oven and it basically smooths the draw from the wall out completely.

[@curtchase3730]

@@retrozmachine1189 Awesome! Thx for input!

[@craftymulligar]

Got microwave think 700 watts it's like 1200 or 1400 watt used. Says it use 1100 watts guess that the efficiency.

[@cleversolarpower]

is really bad... true.

[@trondhansen9896]

your setup uses close to 170amps, your wires are way too thin.

[@cleversolarpower]

121A as calculated in the video. I'm using 4AWG cables rated at 105°C, so they are sufficient.