Tuesday, November 10, 2009

Solar System Size


For us the choice of system size was easy, others can choose as they wish. We are going to partake in a program offered by NC Green Power. Initially this group appears to be a government subsidy to encourage sustainable energy development.

With our local utility company it appears the only metering choice is a buy all, sell all agreement. We continue to buy from them at current rates of what we were told is twelve cents per kilowatt-hour. We sell what our system produces to them for five cents per kwh, and then receive payment from NC GreenPower in the amount of fifteen cents per kwh. This yields potential profit of 8 cents per kwh. Some people design a solar system large enough to breakeven considering this subsidized price. Our fear is that this potential subsidy could change (it has already decreased in amount at least once), so we wanted to design a system that would supply us with all our current needs and be expandable in the event that electric cars become more popular.

There are some websites that would allow one to figure out the figures on our own, but we just sent Joe Sheffield our electric usage over the past year. He told us based on the following data that we would need a 5kw system.


Units are in KWH

Month Usage Amount Billed
(excluding state taxes)
Nov, 2008 579.00 $ 79.71
Dec, 2008 482.00 $ 67.29
Jan, 2009 679.00 $ 84.79
Feb, 2009 861.00 $ 105.17
Mar, 2009 688.00 $ 85.80
Apr, 2009 545.00 $ 70.80
May, 2009 453.00 $ 64.26
Jun, 2009 435.00 $ 62.06
Jul, 2009 776.00 $ 103.85
Aug, 2009 935.00 $ 123.34
Sep, 2009 1014.00 $ 133.03
Oct, 2009 537.00 $ 74.94
Nov, 2009 385.00 $ 57.50

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