723 Spring Street just completed the first twelve months of solar photovoltaic energy generation. The home is LEED Platinum Certified and was constructed to be extremely energy efficient with a geothermal ground source heat pump and engineered wall and roof systems. The SunPower 8.64 kW system generated 12,711 kWhs over the first year of production and provided 44% of the of the total annual energy usage. Based on BTU’s per square foot, 723 Spring Street uses 50% of similarly sized homes. This annual energy reduction is the equivalent of 8 tons of carbon offset or 200 trees. The net cost of the system was $57, 375 (invoice cost) – 15,552 (utility rebate) – $23,547 (federal tax credit) = $29,276 (net cost) or $3.39/watt.
The house also takes advantage of favorable electric usage rates for the geothermal ground source heat pump. Total annual savings were $2,036 and the first year total utility cost was ($62). Based on the solar PV production and electrical usage, the simple payback on the solar system was 11.3 years and the annual ROI equals 9%.