Insulation resistance

Also known as IR test

Insulation resistance is a measured electrical resistance value used to check how well conductors are insulated from each other and from earth.

Insulation resistance is the measured resistance of insulation between live conductors, and between live conductors and earth or the protective conductor path, during electrical inspection and testing. IET (Institution of Engineering and Technology) model Electrical Installation Certificate and EICR (Electrical Installation Condition Report) forms record insulation-resistance test voltage and results in MΩ (megohms) for live-live and live-earth paths. An IR test, or insulation-resistance test, is shorthand for this check. In home energy work the term can appear in circuit test schedules, handover packs and checks around solar PV systems, batteries, EV chargepoints and heat-pump electrical supplies.