Community Renewable Energy

Resource Assessment

Solar energy is a widely available resource, but there are limitations. Solar energy is not available at night, is less available in winter months than summer, and operates at less than maximum capacity in cloudy conditions. For these reasons, solar energy systems typically work at a capacity factor of 10-20%, compared to wind’s capacity factor of up to 35%, or fossil fuel power plants with capacity factors of more than 50%. A more useful characterization of annual energy production is described as kilowatt-hours produced per year, per kilowatt of installed capacity. For example, every 1 kW of PV installed in Portland, OR can be expected to produce 1100 kWh of energy per year.

Other climate zones in the region have their own capacity factors, as the availability of solar energy varies by geography. The effects of climate and latitude on solar energy production can be seen on any solar resource map, or by using one of the many solar energy production calculators available, such as PV Watts or RETScreen. The University of Oregon offers more accurate figures and maps for solar energy production within Oregon’s climate zones.

Despite the importance of resource availability on energy production, other policy and financial factors actually contribute as much, or more, to the cost-effectiveness of a solar energy system. This is why solar energy in Germany, for example, is widely popular and is more cost-effective than in places like New Mexico. The lower average energy production of a solar energy system in Germany (or New Jersey) compared to New Mexico, is far outweighed by the policies and financial drivers in place that increase the value of solar energy in Germany.