A 10% efficient PV system will generate up to 180 kilowatt-hours per square meter. A PV system rated at 1 kilowatt will produce up to 1800 kilowatt-hours a year. Allowing for a loss of efficiency of less than 1% per annum. Such a PV system could generate close to 36,000 kilowatt-hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30 years. This means that a 1Kw PV system generates more than US $10,000 worth of electricity over 30 years. In many countries, preferential rates are paid for solar-generated electricity and various other grants and tax incentives are available that improve the economics of PV.