Electric (PV) water heat vs Gas vs Solar heat
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Electric (PV) water heat vs Gas vs Solar heatPosted by jhleung at June 29. 2008
Re: Electric (PV) water heat vs Gas vs Solar heatPosted by Peter Smith at July 01. 2008
I am building a new house and your math, which seems fine, is very relevant to what I have been considering.
Isn't the other key variable the actual price of electricity given your PV plans? For my SoCal location my electricity costs are projected to be zero so that seems to be make the electric water heater a no brainer.
Plus it invests in equipment where the power source -- PV provided electricity -- is predictable in terms of supply and cost, while the gas choice ties me to less predictable source, particularly in terms of cost.
In your case, in foggy SF, you would need to get comfortable with your PV projections. One tool that may help is this calculator at
Re: Electric (PV) water heat vs Gas vs Solar heatPosted by Antony Tersol at September 17. 2008
If you switch to a time-of-use rate, you can get paid a high rate during some of the time the PV is producing (especially 12-6pm M-F, summer) and pay a low rate off-peak. Since heat is more needed at night and winter (off-peak) you can effectively reduce the cost per kwh produced.
Also, there is a system that combines PV and thermal (taking heat off the PV modules) for a modest increase in cost - see http://www.pvtsolar.com
It at least doubles the energy captured - but the additional is as thermal energy. We've installed 3 of these so far, and about to install our 4th. All well proven components, just used in a novel way.
Being on the west side, you will see 10-15% less energy produced on an annual basis than on the east side. The calculators probably won't show that difference as they don't have that level of discrimination. The impact comes in particular during the fog times - June, July, Aug, and sometimes Sep.