What you say about setting water temp to 145 (so you use less) is true for a resistanve hot water heater where every BTU costs the same) but very very counter productive for a heatpump water heater! Heat pump efficiency is inversly proportional to temperature.
I set my heat pump water heater temperature to 105 degrees where it's efficiency is near 3 to 1. Yes a shower uses almosst 95% hot water and a dash of cold to get the right temperature. But I run the output of the 50 gallon HP water heater into the old 80 gallon resistance tank (super insulated) so that I have 130 gallons a day of storage. That covers demand. I DO have the top coil of the old 80 gallon tank set to 115 so that the resistance BTU's are only rasing the temp 10 degrees! That is 6.5 times less electric than using resistance heat trying to raise from 50F to 115F directly! Bob On Sat, Jan 25, 2020 at 9:18 PM Peter VanDerWal via EV <[email protected]> wrote: > My calculations suggest that not only is an off-grid system about triple > the > price of solar grid-tie, you also have maintenance issues for life AND you > have a two-to-one lifestyle change twice a year. You either DOUBLE your > investment to get enough energy for winter living, and then throw away the > double excess power you have in the summer, or you build for the summer and > then have to live at half power in the winter. AND it cost 3 times as much > for this discomfort than a GT system. > > Dumb (if you have the grid). If you don?t have the grid and they want > $30,000 to bring it in, then of course off grid is good. > > Bob > I guess it depends on where you live. Where I live in Southern Arizona, > we get a monsoon season during the summer a usually fairly clear weather > during the winter. With clear skies and colder temps, my solar array tends > to produce more energy in the month of February than it does in July, and > that includes having 10% fewer days in February. > > I'm still collecting data but so far it looks like I'll need a similar > size array for winter heating as I need for summer cooling. Spring and > Fall is when I'll end up with surplus, however that is also when I tend to > spend the most time working on projects (wood working, metal working, etc) > so I can probably put the surplus to good use. However, solar panels are > cheap these days, so if I end up throwing some energy away, then so be it. > As for the guy on YouTube, I think he discounter heatpump water heaters > too quickly. Yeah that unit may only come with an 80 gallon tank, but that > doesn't mean that you can only store 80 gallons of hot water. You could > easily circulate hot water from that to an external tank. And if you > increase the water temperature, and use a mixing valve, you can increase > your stored BTUs without increasing tank size. > My heatpump water heater is an add on unit, so I can use any size tank I > want. Currently I have a 60 gallon tank, but I added insulation to it and > keep it at 145 degrees, which means to get a comfortable shower temp it's > roughly 50% hot water and 50% cold. In my house we average around 10 > gallons of water per shower (my wife uses a bit more, I use a bit less) So > theoretically that is around 10-12 showers per tank, that could last us at > least 3 days with the HP turned off. > Hot water is what I consider a "want" not a "need", in a pinch we could > live without it for quite a while. Besides, the HPWH only uses about 1kwh > per day. > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20200126/99b9eef0/attachment.html > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/index.html > INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20200126/e66e66fb/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
