We first installed an
18 panel 220w Sunpower system in a near optimized south facing line in August of 2008. This initial install was set as AWNINGS with about 40" of each panel OFF the roof and providing shade for all of our exposed second story windows. I brought in about a dozen PV contractors but only 3 would actually give me a bid on the awning format I demanded. We are most pleased with this installation, as even in full Sacramento Valley midsummer all of our upstairs windows get full shade from the PV panels ! At that same time we also installed a solar hot water system above the PV panels on the east end of the roof area.
From that initial install, we totally wiped out our actual electricity use billing (we still pay a connect fee of about $13/month to Pacific Gas and Electric), and we reduced our annual natural gas bill by about 50%.
We have a new house with pretty much state of the art insulation, etc. But since we are in a brand new development there are NO trees of any size to compromise solar input to the panels.
Anticipating replacing both of our Toyota hybrids (Prius and Camry) with the Chevy Volt (already now in the garage) and the LEAF (delivery in February), I further added a second 7 panel Sunpower 220w system with a second inverter (our original inverter was maxed, so we had to have the second) in October of 2009. These 7 panels are placed in a conventional format actually ON west end of the roof above the earlier awning format install.
With the double PV system, last year we generated 1200kW MORE than we used and we had a "credit" with PG&E of $438 on our annualized bill for electricity (though PG&E will not be paying us that credit, since they don't have to for 2009-10, as the required payback law only became effective onward from January 2011 apparently). Anyway, with time of use billing and charging our EVs during that midnight to 7 am period and also on the more open low rate weekend times, I project that we will still have ZERO annual electricity use costs even with both of the EVs getting their power mostly at home and also be cutting our annual vehicle upkeep (fuel and service) costs from around $2300 per year to around $300 per year.
Our max solar PV production runs around 36kW/day in the peak periods, and our baseline house USE tends to be around 16-18kW/day; we try to avoid actually using significant power draw in peak periods and with the insulation quality of the home, we don't need our AC unless we have summer temperatures above around 98 degrees. We do our washer and dryer loads in off-peak times, even using the delay timer on the machines themselves to optimize that negative impact on our bill. Further we did have PG&E switch us to the E9 rate (for EV owners), so that gives us an off-peak cost of around $0.06/kW and a PEAK cost of around $ 0.30/kW. Hence we generate excess and get credit at $ 0.30/kW and use most heavily at the off-peak rate of $ 0.06/kW.
We also have, through Sunpower online monitoring of our system with graphic summaries of hourly, daily and monthly output through their online site.
Life seems good!