The grid-tied 12.9 kW solar-electric system was predicted to provide 91% of the facility’s electrical needs, based on a comprehensive load analysis performed by Solar Design Associates. Accounting for day-to-day demands was fairly straightforward—eight staff members working five, eight-hour days per week and running at least four computers, various lights, and other appliances at any given time. Operational loads were fairly predictable as well—exterior porch lights, parking lot lights, an Energy Star refrigerator, a dishwasher, and a washer and dryer.
It was the unpredictable higher-than-normal demand for special events, meetings, and various classes that complicated the system sizing. While the annual electrical load was estimated to be 15,457 kWh and the PV system was estimated to generate 14,127 kWh per year, it turns out that these estimates were slightly conservative. In its first year of production, the PV system actually generated 19,000 kWh, while the building consumed 18,000 kWh, showing the potential for a slight surplus of energy for some years.