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Old 07-15-13, 10:37 PM   #43
ELGo
Helper EcoRenovator
 
Join Date: Apr 2013
Location: Albuquerque
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@#25

I was curious about the $ arithmetic ...

A gallon of heating oil has about 41 kWh. Assuming about a 60% burn efficiency for the boiler (is that about right ?),a gallon will supply 24.6 kWh of heat for about $3.50, or 14 cents a kWh.

PVWatts says that a perfectly sited fixed solar collector for Boston averages 1.54 kWh a year per watt installed if the derate is 1.0 . If your tilting array is E-W you will collect another ~ 30%, or about 2 kWh/watt*year.

What did the PV setup cost ? If say $2/watt and 25 years of use then cost per kWh is 200/50 = 4 cents.

If you are only willing to track out 10 years, then the $2 buys you 20 kWh, = 10 cents a kWh.

So I would say this is not a giant $ saver, but you no doubt had fun setting it up, and it is clean energy. TWO THUMBS UP.

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It is much less obvious to me that the ASHP would be something I would add since it's annual average COP is less than 2 in Boston, and most of your energy is now supplied from PV.Moreover, the ASHP and PV are not complementary in the sense that during the cold winter when PV is down, the ASHP COP will be poor (approaching 1).

Last edited by ELGo; 07-16-13 at 12:16 AM..
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