Domestic Energy Assessors inspect homes to produce Energy Performance Certificates (EPCs), which show a property's energy efficiency and typical energy costs. They gather information such as the building's age, layout and construction, measure relevant areas, and record features including insulation, windows, heating systems, hot water controls and lighting. The assessment is generally visual and non-invasive; assessors may ask for evidence of improvements or heating-system details where these are available. Using the information collected, an assessor calculates an energy-efficiency rating and prepares recommendations for potential improvements, such as upgrading insulation or heating controls. EPCs are commonly needed when a home is sold or rented, subject to the applicable rules and exemptions. In the UK, domestic EPCs must be produced by assessors who are members of an approved accreditation scheme, and certificates are lodged on the relevant national register.