The following graphs illustrate baseline production PV data for regions across Massachusetts for the years: 2003, 2004, 2005 and 2006. Many of our customers report their annual production to us and some their monthly production. We selected 14 monthly reporting installations which typify our averages for all customers. The notes below each graph provide further detail on the selections. These PV systems range in size from 1.kW up to 31 kW; capacity is represented as if all were 1.2 kW DC capacity systems or nominal 1 kW systems. All data represents the usable electricity customers receive from their PV systems from their “Revenue Grade” Solar kWh meters.

These tables represent a portion of the PV Production Analysis Project completed brilliantly by Rebecca Knights, a senior Environmental Science Major at Massachusetts College of Liberal Arts (MCLA) as part of her internship with BPVS. Chris Kilfoyle and Bryan Waryjasz of BPVS provided guidance; Bryan prepared the web page. Please cite BPVS when using this data.

Capacity Factor | AC kWh Production of a 1 kW system | Massachusetts Customer Annual Average Customer VS. Customer production

Capacity Factor is an indicator of the reliability of electric generating plants. Some coal fired and nuclear power plants will have a capacity factor in the high 90s’ percentile. PV is an intermittent resource. If these PV systems produced their rated capacity every hour (8760 hours –all year, night and day) they would have a 100% capacity factor. The data shown is from our sample. The annual capacity factor from annual production data of seventy customers results in an average of 13.9%. Outliers are 8% and 17%. These Towns are all in Massachusetts. Tilt angles of the arrays are given for comparison. Note the four Williamstown sites with differing array tilt angles.

BPVS Installed systems AC kWh production vs Estimated production

This graph shows the actual monthly production averages for fourteen sample customers over the last three years compared to our 1998 -2004 sample of 11 customers and to the predicted production based on National Renewable Energy Tables for Boston- 20 year meteorological data(NREL Estimate) and the predicted production base on the Massachusetts Technology Collaborative Estimating software.Both NREL and MTC use Boston weather data; our sample of customers actual production is biased toward western MA. The annual variation in production is significant however the rule of thumb that every watt of capacity will produce 1 kWh of production is sound.

Average Annual Customer KWh Production

Note the annual production range for various tilt angles and orientation to south. The variation is not wide. System (L) (Howden Farm ) is a pole mounted array whose tilt angle is seasonally adjusted in Spring and Fall.

These two graphs show the annual production data from two customers with identical PV systems. The 2.4 kW(DC-STC) systems at the SENIE Residence in Bolton, MA and the PIASECKI System approximately 100 miles west in the Berkshire County town of West Stockbridge, MA . Both systems are on identically pitched roofs and at the same azimuth of 180 degrees (true south)orientation.