Tankless Electric Water Heater

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Old 01-21-19, 03:26 PM
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Tankless Electric Water Heater

I plan to add a detached unit in California Bay Area home. I only plan to feed electricity to this unit, so that heating and water heater need to be powered by electricity. The unit is 700sf with 3 person live inside in California Bay Area which has mild weather. However, I heard bad review on electric tankless water heater. Not sure if tankless water heat would provide enough warm water for 3 person comfortable living.
 
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Old 01-21-19, 05:19 PM
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It can but you're going to be very surprised at how much electricity it requires.
No chance of using a gas heater instead?
 
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Old 01-22-19, 04:46 AM
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Straight electric resistance heating is probably the most expensive way to make heat. It's generally acceptable when doing it just for hot water but if you'll also be using it to heat the house/cottage then it will be very expensive to operate. You might consider a mini-split heat pump to handle the heating and cooling and just let the water heater heat water for sinks and showers.
 
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Old 01-22-19, 08:55 AM
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Mini split AC's in heat pump mode provide 3 times BTU output of electric resistance heaters at same KW input.

Look for ratings of COE = Coefficient of Efficiency and COP = Coefficient of Performance.
 
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Old 01-22-19, 12:06 PM
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COE 0f 3.0 is 3 X 1 KW (3,412.14 Btu/h) = 10,236.14 Watts
 
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Old 01-22-19, 01:07 PM
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You are correct. The heating and cooling will be with slip A/C unit be run by electricity. The tankless water heater for hot water only, meaning shower and kitchen usage. Can this one heat enough hot water for 3 adult usage?
https://www.amazon.com/Stiebel-Eltro...s%2C193&sr=1-2
 
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Old 01-22-19, 02:02 PM
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The page you linked includes a chart to help determine it's suitability. Whether or not it will work depends on how you will use it and the water temperature coming into your home. It's all about how much hot water you use at one time. Showers in a row one after the other would be no problem. Where you really need to study is if you intend to do laundry, run the dishwasher and have two or three hot showers going all at the same time.
 
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Old 01-23-19, 10:56 AM
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Thanks @Pilot Dane for your input. Do you have practical experience of using this type water heater? How good is it? By looking at the chart and google the internet, I felt the chart is kind of off from what I found from the internet. The chart says, a shower head is 1.5 GPM while internet says typical shower head is 2.5 GPM. And also, I asked around the contractors in the Bay Area of California, they indicate that electric tankless isn't good for use, not just flow rate, but also it is possible hard to pass title 24 building code. This had me concern whether it is practical to install the electric tankless water heater. This was the reason I post the question here to seek advice.
 
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Old 01-23-19, 01:53 PM
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Sizing of mini splits to match actual design load is very important. Here is good article on subject:


https://www.contractormag.com/hydron...ight-equipment
 
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