Comparing standard recommendations with site-specific measurements for sizing residential alternative energy applications

Alternative energy supplies, specifically photovoltaics, are reaching the point where they are truly cost-competitive options with respect to the local supply. However, they remain capital intensive on the front-end of the installation. The major up-front costs are for the panels, the electronics and controls, and the energy storage elements. Standard assumption sets exist for determination of the required panel area and energy storage capability, and these determinations drive the specifications for the electronics and controls. Given the (relatively) large initial costs of photovoltaic projects, it is necessary for the assumption sets, which ultimately drive the cost, to be as accurate as possible. In this paper, measurements of both available solar energy and actual energy consumption for selected residences in the United States are presented and used to demonstrate more accurate procedures for specifying photovoltaic equipment including appropriate battery energy storage devices.