How to Size Your Tankless Water Heater Properly

We get the question a lot. It's probably the question people ask most.
You can always call us to ask about what size tankless electric water heater you need. You can also go to our website to see what tankless water heater you need by using our chart right on the miamiwaterheater.com home page.
Always give your self a cushion when sizing your tankless electric water heater and if you're unsure, you can always call us at 305-633-2656.
This video should help you determine whether you need a RHEEM RTEX 13, RHEEM RTEX-18 or RHEEM RTEX-27.
Remember that Miami Water Heater has the best prices and warranty on these units.
Water heaters is all we've done since 1949.

[@chrismack3516]

He really means it when he says, "even if you don't buy from us, call me if you need help!" I even called him about sizing a natural gas outside unit for metro Atlanta, and he is in Miami! I was going to oversize the unit and buy a 9.5 gpm unit when I only need an 8.4 gpm, and as he said, "that's plenty for a 2 full bath 4 bedroom home, unless someone wants to draw a bath on the coldest night of the winter." I am SO appreciative of your help and guidance! Many thanks to this gentleman who also took my call at 7pm on a Monday night!

[@miamiwaterheater2281]

thank you for lettimg people know that yes i will help whether you are going to buy from me or not and like Chris shared i answer after hours also

[@aledwards2363]

I just called Miami Water Heater and spoke to a gentleman who was unbelievably knowledgeable and helpful. I told him I was calling from Virginia Beach, and he still treated me like one of his customers. He stayed on the phone for about 20 minutes graciously answering all my questions and concerns. Unbelievable in this world! When I commended him for how well he was treating me, he said that's how Miami Water Heater has stayed in business for so long - great customer service. This company is a credit to their profession. I would trust Miami Water Heater for any job if I lived in their region. Thank you again for being such great, polite, knowledgeable experts.

[@miamiwaterheater2281]

Thank you for the kind words glad I could help

[@brysenkelly663]

Guys legit! Just called from Norfolk,VA! Gave me all the info with no flack at all! Really was surprised, businesses like them are extremely rare to come by!

[@AnthonyTSolano]

Fuckin love this guy!!! True legend! Coached me up, right after I watched the video while putting my 4 yr old twins to sleep, the struggle of a dad! This guy is amazing !!!

[@miamiwaterheater2281]

thank you for the kind words and taking the time to call last night. i hope i was helpful

[@Chris-vx5kp]

I live in south Texas, and the hard water is killing our water heater. I plan to replace it with a tankless water heater, and this video has been so much more helpful than all the crap out there.

[@miamiwaterheater2281]

you're welcome but the hard water will cause problems with the tankless unit eventually

[@Chris-vx5kp]

@@miamiwaterheater2281 Our hard water fucks up everything. A water softener is also on the list of things to buy. The flushing ability of a tankless just seems superior to the current tanked water heater.

[@robertn-mj9sm]

I too, called them. All my questions were answered. Highly recommend MWH.

[@vinniehamada]

CARLOS is the man. super helpful. honest and very knowledgeable. thanks for the help, carlos

[@miamiwaterheater2281]

Thank you for the kind words I'm glad i could help

[@lilpandaexpress3]

Thank you for this video! Very kind to be so helpful, you've really helped me out in California...time for a new water heater and this time we are going tankless! God Bless you!

[@miamiwaterheater2281]

We sell the Rheem tankless on our website if you are interested Miami water heater.com

[@matthewglover1784]

From Michigan. Ironically you sized the exact specs for my home. Will use your charts and my temps to verify. Thank you so much for the information.

[@miamiwaterheater2281]

my pleasure glad i could help

[@robertgoodfellow5564]

I live in michigan, I bought a 27kw . I have 1 bathroom , keeps giving me a water pressure error, don’t know what to do, too high of water pressure code I guess

[@gilbertsegovia5983]

He really means it, if your new like I am and need help give him a call he will gladly help. Coming from me. A person from Texas.

[@CARLOSSANCHEZ-vz3fp]

Thank you for letting people know that I mean it when I say I’ll help you whether you are buying from me or not

[@ThomasGerlach4Tri]

This company is genius. This is how you build a brand and generate a ton of Google juice. You should be taking notes if you are a small business owner.

[@miamiwaterheater2281]

thank you for your kind words and if you have any questions please let me know

[@raysantana7212]

You’re the best. Wishing you the best. You’re honest and that says a lot about you . Thank you 🙏 God bless you

[@miamiwaterheater2281]

thank you

[@InvestAndGrow2020]

Thank you!

[@GodsIntricateDesigns]

This was such an amazing explanation. Thank you for taking the time to make this video! 😀

[@miamiwaterheater2281]

my pleasure if you have any questions please don't hesitate to ask

[@peach200005]

Excellent info about temperature in/ out. I appreciated and I will be calling you guys. 👍👍👍👍👏👏👏👏

[@miamiwaterheater2281]

thank you

[@johnberry1107]

You do fine explaining. Just a lit bit of a fast talker. Slow down and let us absorb. Stay safe. Thank you.

[@miamiwaterheater2281]

Thanks, will do!

[@ronnavarney7318]

Thank you for information ur truly a money saver.i have 2 bathroom wth a large jacuzzi bathtub what do I need? Plus kitchen and washing machine

[@miamiwaterheater2281]

glad I could be of help

[@darthmal]

It woul'da helped if you provided the links. I went to the website and gave up looking for that information.

[@vica153]

As far as I can see, there is no real downside to the higher output units. The minimum flow rates are usually the same. They are packaged in the same box. The difference in price of the heater itself is nearly negligible compared to the whole project.

[@OpenMindedForever]

Wow! Great video! Can you answer this case scenario question: If I buy an 8-unit rental apartment that requires a minimum 80-GPM cold water (40-degree) supply from the meter for 36-Fixtures (using the UPC Chapter 6 Hunter's Curve Appendix math), how many GPM will a 300-GPH tank heater provide each of the hot water fixtures (e.g., each of the 8 non-water-conservation tub-spouts via their 10-GPM maximum flow rate Moen spec mixing valve)? Is 300-GPH limited to 5-GPM (not 10-GPM) maximum h/w flow rate per 1-hour (300/60) -- (e.g., 8-units filliing 60-gallon tubs with 30-gallons of h/w at the same time = 240 gallons @ a 6-minute 5-GPM fill rate)? Would I need a 600-GPH tank to provide the 8-Units their 10-GPM maximum Moen spec mixing valve h/w 3-minute fill rate? Yes, I know Hunter's Curve claims the odds of all 8-fixtures (or all h/w fixtures) being used a the same time is a 1% peak load chance. But I like to plan for worse case scenarios:)

[@miamiwaterheater2281]

these questions are for an engineer which I am not . with that said most manufacturers will help you size you unit and have engineers on staff. i can tell you that in miami an 8 unit apart building uses a 75 gallon 70,000 btu commercial heater and a 36 unit apartment building uses a 76 gallon 199,999 btu commercial water heater

[@IamMimi_2017]

I wish you were here in KY!

[@miamiwaterheater2281]

I'm not in KY but I'm just a phone call away if you have any questions

[@IamMimi_2017]

I was just checking out your website as you suggested in the video. I may be calling you! Thanks!

[@miamiwaterheater2281]

I'll be waiting

[@britj14]

What about using dishwasher or washing machine at the same time?

[@miamiwaterheater2281]

Doesn’t really come into affect unless you plan to use both at the same time as you use both your showers

[@keithkareiva9615]

Good video, good information, and I clicked on the link.......Great prices!!! Just wondering, I'm retiring and moving to Michigan and will be installing a soaker tub. Is it worth it to consider a tankless, should I get two, or should I go with a traditional tank water heater? Thanks for the video and info.

[@miamiwaterheater2281]

for a soaker tub i'd recommend a tank heater because a tankless would work but it would take a really long time to fill

[@ronnavarney7318]

Can u tell me my water is so high in calcium its burnt up 2 heating elements a yr will a tankless be a bad idea?

[@CARLOSSANCHEZ-vz3fp]

No the tankless will have the same problem probably even worse

[@greenis3006]

So if I'm building a b&b in Pennsylvania and the main house will have 9 showers with 6 heads each (though I will I inform guests to only use 2 spray options at a time, max 4 heads), how many Navien propane 199k btu/h would I need? Or would it be better for water pressure to break the building down into zones and have one tankless per zone? We will have a 2" line from the street at 128psi and then drop it to 75psi.

[@miamiwaterheater2281]

i would split them becasue you can be sure that the teneants will follow your instructions

[@eduardopereira4119]

I live in south florida. Do we have to calculate how many showers will be on at the same time? I have a two bathroom house, planing on installing an outdoor shower in the near future and a hook up to a camper trailer. So that will possibly be a total of 4 showers. Ive installed a 27kw ecosmart. Did i go too big? I mean, when will all the showers be on at the same time? Will i same some money on energy if i go a size smaller? Second question: now some of my lights flicker when the water heater goes on, how do i fix that?

[@eduardopereira4119]

Can i go a size smaller?

[@miamiwaterheater2281]

No you didn’t go to big for 4 showers and the lights flicker because the electric is not done properly

[@AngelWilkinsonRealtor]

Great info, thank you.

[@miamiwaterheater2281]

thank you for the review

[@sylviagm]

Thanks, great info! Does it help to know what's on site at the moment? I have a 40 gallon tank, 4,500 W and 240 V. One double pole 30 amps. Central Florida, two people, two bathrooms house, but only one shower in use, so I think an 8 or 11 will be good? Is this a whole house unit? What are the requirements? Will I need to change wires, etc? Do you happen to work in Central FL, or ship here? Thanks for any help, I've been taking cold showers for a week now, lol! Still trying to understand. Also, how about condensing and non-condensing units?🥴

[@CARLOSSANCHEZ-vz3fp]

Yes the 13 will work. You will need 240 volts 60 amp breaker. Yes you will need to change the wire to 6 gauge

[@sylviagm]

@@CARLOSSANCHEZ-vz3fp Thank you!

[@shenoyglobal]

do you install water heaters? or just sell them (this is for a new build)

[@miamiwaterheater2281]

we do install our own heaters

[@shenoyglobal]

@@miamiwaterheater2281 do you also install Rinnai

[@sbuzz5889]

gas is good electrical consider total amps = service change + $ 3500.00 100 + amps/alone try cooking @ same time w/ heater faucet and micro

[@miamiwaterheater2281]

i have no idea what you are trying to say

[@henrycruz45cal]

Why do you ask them what their incoming water temp is when you already know? You start the conversation trying to make them feel stupid?

[@miamiwaterheater2281]

We get calls from all over the United States so we ask because we don’t know where the customer is located. We are definitely not trying to make our customers feel stupid

[@eyecandylaserandwellness]

Hilarious…

[@RaiderNation86]

1 shower, avg.temp 40 to 50, what do you recommend?

[@miamiwaterheater2281]

the rtex18 would be best but you might be able to get away with the RTEX13