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Old 11-13-16, 03:46 AM   #9
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
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Oilpan,

I have used a tankless propane water heater (CEC 170 VP) for over 25 years (no natural gas available), but am considering the use of a tankless electric for a client.

Didn't know the real world kWhr consumption of an electric unit in terms of family use.

Based on your inputs (all reasonable for my area), each gallon requires about 1/12 kWhr ($0.01) to bring from 60 to 110 F. Is 50 gallons per day of hot water reasonable (family of four)?

That 50 gallons would be ~ 4 kWhrs per day.

This client is considering a 80 G (320 L) preheat tank where the water temp is brought up by a variety of means to 90 degrees F or so. This would be several hot water solar panels as well as the desuperheater from a geothermal heat pump.

Obviously, the higher the pre-heat temperature, the lower the hot water kWhr needs . . . .

Am also assuming that the tankless units control output water temp and do not just boost water temp by 60 degrees F.


Steve
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consulting on geothermal heating/cooling & rational energy use since 1990

Last edited by stevehull; 11-13-16 at 04:42 AM..
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