On Jan 12, 2015, at 8:35 PM, Robert Bruninga bruni...@usna.edu wrote:
Compare the 60% efficiency of the PV/Heatpump water heater to the 50% losses
half the year of the 70% thermal panels and higher cost and the PV panels
with heatpump water heating win hands down.
I hadn't heard of heat pump water heaters before this discussion. Something
like that could, indeed, tip the balance.
What happens to the cold side of the heat pump? Can that be used to reduce air
conditioning load in summer?
As of a few years ago, the return on investment, the payback time, for solar
hot water was better than that of PV -- and that included maintenance every few
years, electricity to heat the water on cloudy days (though much less
electricity since you still get a substantial amount of warming), and so on.
But it's obviously a rapidly-evolving field. If heat pumps really are coming to
water heaters, that's huge not just for PV adopters but energy efficiency
across the spectrum.
If my own system lasts a few more years -- and there's no reason it shouldn't
last a few times a few more years -- then it'll have paid for itself. Be nice
to make a sizable profit off of it by getting it to last that few times a few
more years, but, if it dies prematurely, I suppose an all-electric replacement
will have to be on the short list as well as a drop-in equivalent replacement.
b
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