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Solar Photovoltaic Performance Report

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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.


Description of the Two Systems
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







Performance of the Two Systems
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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