July 27th, 2010 by Kenric
This post is based on Another Investor’s comments in the previous solar post about my green home.
When the solar power rep was here he pulled up the stats from another home in Scottsdale. This home was a 9.8kW system producing 32kW a day in June. I would assume that this number is close to the maximum that the system could ever produce. I was told that our solar systems are limiting by our 200amp circuit breaker, so even if I had unlimited roof space I couldn’t put a 100kW in my house without upgrading to a 1000amp breaker.
So based on the 32kW a day, I took a look at my electric bill. For June I used 1200kW during 9am to 9pm peak hours. 1200 – 32×30 = 235kW. Which is really good.
But lets look at the whole bill.
Off peak I used 1544kW. Total kW usage would be 1779kW. I pay $0.14 per KW on peak and $0.02 off peak. Just in straight kW savings the solar panels saved me $134.00. But there are all sorts of other fees like delivery charge, etc… that are prorated by kW usage. Without going into the calculation details I guessitmated that I have additional savings of about $35. So total savings from the solar system is estimated at around $170.
My bill was $350 for the month of June, so solar would have cut my bill 50%. I did the same calculation for May and came up with a $158 savings on a $280 bill. Which isn’t bad. But I guess what I’m seeing is that at maximum sun my solar panels can produce or save about $170 a month.
My average bill is $220 a month, so the savings is pretty significant at $170 month. However, that assumes that every month has sufficient sunlight to produce 32kW a day which we know isn’t true.
If it was as easy as plugging $170 x 12 months = $2040 a year of savings, it would be easy to calculate your payback period. I believe that Solar City guaranteed at least 10,000kW of electric generated or they would pay you for any amount under. 10,000kW comes out to 27kW a day.
BTW, I think that a 9.8kW system could only cost $12,000-$15,000 now with all the rebates. At $12,000 we are looking at a minimum 6 year pay back.
Thanks for making me type this out. It really helps me more and I’ll looking into the cost of buying a system or building one.
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