Numbers, numbers, and more numbers. There is so much to know and consider when you install photovoltaic panels to produce your own electricity. This article will report the numbers for two installations, one in Rexford (Southern Saratoga County) and one in Saratoga Springs. Both are producing electricity for private residences. Both systems are tied to the grid.
Before we get lost in the numbers, the most important consideration is that your roof or ground mount system will produce clean, green energy for at least 25 years. This is a tremendous contribution to your own energy use, but also eases the strain on the grid. Conservation stills plays a big part in keeping your energy use low, and hopefully within the bounds of your own production.
A few things I have learned that were unexpected. When you produce all your electricity you pay a delivery charge (<$17/month), but no supply charge. The panels are not as efficient in the heat. Long hot days do not produce more than cooler shorter days. Snow less than 3 inches deep will slow production, but does not stop it. Snow is slow to go off of the roof panels when there is little sun. On a very cloudy, dark, rainy day, the panels will still produce 1-3 kWh. Battery back-up works seamlessly, not even interrupting a phone call.
| Property | Rexford, NY | Saratoga Springs, NY |
|---|---|---|
| Roof Mounted | yes | yes |
| Number of Panels | 24 | 16 |
| Production of each panel | 190 Watts | 215 Watts |
| Total (DC) | 4.56 kW | 3.44 kW |
| Tilt (in degrees) | 30 | 33 |
| Battery Back-up | yes | no |
| Panel Manufacturer | Evergreen | SunPower |
| Inverter | Sunny Boy | SunPower SPR 3000m |
| Property | Rexford, NY | Saratoga Springs, NY |
|---|---|---|
| First day of operation | 12/15/2008 | 3/20/2010 |
| Calculations as of | 9/8/2011 | 9/6/2011 |
| Total Production | 14,027 kWh | 5,961 kWh |
| Daily average over life | 14.8 kWh per day | 11.1 kWh per day |
| Highest daily production | 30 kWh | 21 kWh |
| C02 Saved | 23,800 pounds | 10,090 pounds |
| Percent of household need | 70% | > 100% |
| Summer daily use | 13 kWh | 9 kWh |
| Winter daily use | 22 kWh | 12 kWh |
Nancy is a retired secondary teacher. She built and lives in an active and passive solar, high thermal mass home. She is an avid gardener and helps others to learn how to garden.













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