3 ms·

A pv at 25% efficiency attached to a heat pump with a COP above 4 is still above 100% so still beats thermal. And yes you can have both, but the cost to have th

A pv at 25% efficiency attached to a heat pump with a COP above 4 is still above 100% so still beats thermal. And yes you can have both, but the cost to have the installers add a few extra KW of pv is less than getting other installers out to do an entire solar thermal system, so what's the point? Payoff as in if you buy a pv system it will pay for itself quicker than a thermal system. Electricity is more expensive and valuable than 'heat' (read gas substitute) so even if the pv system is more expensive, the savings are greater, which offsets the higher purchase price. Hey if you want to shower under a black bucket, go for it :)

droithomme 8y ago
> A pv at 25% efficiency attached to a heat pump with a COP above 4 is still above 100%... Could you name the particular brands and models of PVs you are using that produce 25% in the field? 15% under ideal conditions is more typical and your 25% is above current state of the art available for home installation. Also interested in your heat pumps above 3. Are these geothermal? If not, who makes them? Normal set up is going to be 15% max on the PV and 3 on the heatpump, for 45% max, but more typically 25% as the PV is seldom set up to capture ideally.
- benj111 8y ago
  I was quoting my parent on the 25% efficiency figure. "The COP for heat pumps range from 3.2 to 4.5 for air source heat pumps to 4.2 to 5.2 for ground source heat pumps" https://en.m.wikipedia.org/wiki/Heat_pump https://en.m.wikipedia.org/wiki/Heat_pump
caf 8y ago
The COP of a heat pump hot water heater is strongly dependent on the ambient and current water temperature. You get the best COP heating from cold, but it's not often that you have to reheat an entire tank of cold water. The actual achieved COP in normal use is more like 2-2.5.
supermatt 8y ago
Sometimes all you need is a black bucket. If you want to throw an 8KW solar array and a $3000+ heat pump at a shower then go for it! :D

droithomme 8y ago

> A pv at 25% efficiency attached to a heat pump with a COP above 4 is still above 100%... Could you name the particular brands and models of PVs you are using that produce 25% in the field? 15% under ideal conditions is more typical and your 25% is above current state of the art available for home installation. Also interested in your heat pumps above 3. Are these geothermal? If not, who makes them? Normal set up is going to be 15% max on the PV and 3 on the heatpump, for 45% max, but more typically 25% as the PV is seldom set up to capture ideally.

benj111 8y ago
I was quoting my parent on the 25% efficiency figure. "The COP for heat pumps range from 3.2 to 4.5 for air source heat pumps to 4.2 to 5.2 for ground source heat pumps" https://en.m.wikipedia.org/wiki/Heat_pump https://en.m.wikipedia.org/wiki/Heat_pump

caf 8y ago

The COP of a heat pump hot water heater is strongly dependent on the ambient and current water temperature. You get the best COP heating from cold, but it's not often that you have to reheat an entire tank of cold water. The actual achieved COP in normal use is more like 2-2.5.

supermatt 8y ago

Sometimes all you need is a black bucket. If you want to throw an 8KW solar array and a $3000+ heat pump at a shower then go for it! :D