Capacity factor gives the ratio of the actual output of an energy production technology over a period of time as against its output if it had operated at full its full nameplate capacity constantly. Capacity factor is calculated by dividing the full capacity figure by the actual production. Capacity factors vary greatly between various energy technologies. Biogas has a high capacity factor of about 80%, whereas wind turbines have low capacity factors of about 20%. This is because the performance of the former does not depend on unreliable inputs like the available wind speed limited range of the latter. Capacity Factor is an essential bookkeeping ingredient when comparing the capital and maintenance costs of different technologies.