What is PAT testing?
By Azzeddine Kebbi, NAPIT-registered electrician and director of Kebbi Electrical Services · Updated 10 November 2026
PAT testing (portable appliance testing) is the inspection and testing of electrical appliances that plug in, such as kettles, heaters, power tools and extension leads, to check they are safe. Each item is checked by eye, tested with a PAT tester and labelled.
What is checked
Visual inspection
Damage to the plug, cable and casing, the right fuse, and signs of overheating.
Earth continuity
For Class I (earthed) appliances, proves the earth works.
Insulation resistance
Checks the insulation between live parts and the casing.
Leads and extension leads
Checked for polarity and damage too.
Is it a legal requirement?
There is no law that says “you must PAT test”. But employers and landlords have a legal duty to keep the electrical equipment they provide safe. PAT testing, with records, is the usual way to show you have done that.
How often?
It depends on the type of equipment and how it is used. Items that are moved around a lot, or used on building sites, need checking more often than a computer in an office. The IET Code of Practice gives guidance on frequencies, and your tester can advise.
Common questions
Who needs PAT testing?
Businesses, landlords who supply appliances, HMOs, schools, shops and offices commonly use PAT testing to show their equipment is safe.
Do landlords need PAT testing?
Landlords must make sure appliances they supply are safe. PAT testing is the usual way to prove it, and HMO licences often ask for it. It is separate from the EICR landlords need.
What is the difference between Class I and Class II appliances?
Class I appliances rely on an earth connection and have a three-core cable. Class II appliances are double insulated, marked with a square inside a square, and need no earth.
What happens if an appliance fails?
It is labelled as failed and should be taken out of use until it is repaired and retested, or replaced.