Portable appliance testing keeps workplaces and rental properties safe across the UK, but the results can leave many people scratching their heads. Numbers on a screen, pass or fail indicators, readings in ohms and megaohms — it is easy to feel uncertain about whether you are looking at a good result or a problem waiting to happen. Understanding what a good score on the PAT test actually means is essential for anyone responsible for electrical safety compliance.
PAT testing, formally known as in-service inspection and testing of electrical equipment, produces specific numerical readings rather than a single percentage score. Each test measures something different, and the thresholds for passing or failing vary accordingly. Getting to grips with these figures is not just about satisfying a checklist; it is about genuinely knowing that the equipment people use every day is safe.
What Is the Average Score for a PAT Test?
There is no single average PAT test score because the results span multiple individual tests, each with its own unit of measurement and acceptable range. The two most significant electrical readings are earth continuity resistance and insulation resistance, and they work on entirely different scales.
For earth continuity (also called the earth bond test), a typical result on a short-lead appliance falls somewhere between 0.01Ω and 0.10Ω. Insulation resistance readings, on the other hand, tend to be many magnitudes higher, with most healthy appliances returning values well above the minimum 1MΩ threshold. Comparing these two sets of numbers directly would be meaningless, which is why PAT testing is best understood test by test rather than as a single aggregate figure.afe for continued use in the workplace.mains electrical risk.
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What Is an Acceptable Reading for a PAT Test?
The acceptable readings for a PAT test are defined by the IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment, now in its fifth edition. These figures give testers a clear reference point for determining whether an appliance is safe to return to service.
For Class I appliances (those with an earth wire), the earth continuity reading must come in below the formula (0.1 + R) ohms, where R represents the resistance of the supply cable. For a standard short lead, this effectively means staying under 0.1Ω. Insulation resistance must register above 1MΩ for Class I appliances when tested at 500V DC, and above 2MΩ for Class II (double-insulated) appliances. Anything below these thresholds is a fail.
| PAT Test Type | Pass Threshold | Notes |
|---|---|---|
| Earth Continuity (Class I) | Below (0.1 + R) Ω | R = cable resistance; short leads typically under 0.1Ω |
| Insulation Resistance (Class I) | Above 1 MΩ at 500V DC | Use 250V DC for IT equipment with surge protection |
| Insulation Resistance (Class II) | Above 2 MΩ at 500V DC | Double-insulated appliances; no earth test required |
| Leakage Current (IET 5th Ed.) | Below 5 mA | Applies to both Class I and Class II equipment |
| Earth Continuity (extension leads) | Below (0.1 + R) Ω | Longer leads have higher R values, raising the ceiling |
Is a Score of 20 on the PAT a Good Result? Understanding Earth Continuity Readings
When people ask whether a score of 20 is good on a PAT test, the answer depends entirely on the unit being displayed. If your PAT tester is showing 20 milliohms (0.02Ω) for earth continuity, that is an excellent result and well within safe limits. It indicates a solid, low-resistance connection between the earth pin and the appliance casing.
If, however, a reading of 20 appears alongside an insulation resistance result measured in megaohms, the context shifts completely. A reading of 20MΩ for insulation resistance is considerably higher than the minimum 1MΩ threshold, making it a strong pass. Always check the unit displayed on your PAT tester before drawing conclusions, as misreading the scale is one of the most common sources of confusion for those new to testing.
Is 450 on the PAT Test a Good Reading? Making Sense of High Insulation Values
A result of 450 in the context of PAT testing almost certainly refers to insulation resistance measured in megaohms. If so, 450MΩ is an exceptionally good reading, sitting far above the minimum requirement of 1MΩ for Class I appliances. It suggests the insulation is in excellent condition with very little leakage current making its way through to earth.
In practice, many modern appliances in good working order return insulation resistance figures ranging from a few megaohms up to several hundred megaohms. The higher the reading, the better the insulation quality, though any result above the minimum threshold is considered a pass. What matters most is that the reading does not fall below 1MΩ, because that is where the risk of electrical shock or fire begins to increase substantially.
The Health and Safety Executive provides guidance on maintaining electrical equipment safety in the workplace, and employers can refer to HSE advice on electrical safety at work for a broader understanding of legal obligations under the Electricity at Work Regulations 1989.
| Insulation Resistance Value | What It Indicates |
|---|---|
| Below 1 MΩ | Fail: Unsafe for use, remove from service immediately |
| 1 MΩ to 9 MΩ | Borderline pass: Monitor closely, may indicate ageing insulation |
| 10 MΩ to 99 MΩ | Good: Insulation in acceptable condition |
| 100 MΩ to 499 MΩ | Very good: Healthy insulation with minimal leakage |
| 500 MΩ and above | Excellent: Insulation integrity is high |
Who Can Carry Out PAT Testing and Record the Results?
A frequently misunderstood aspect of PAT testing is who is actually permitted to do it. In the UK, there is no legal requirement for a person to hold a formal qualification before carrying out PAT testing, but they must be deemed competent. The Electricity at Work Regulations 1989 place the responsibility on employers to ensure testing is conducted by someone with sufficient knowledge and understanding to interpret the results correctly.
In practice, it has become widely accepted for individuals carrying out PAT testing professionally to hold the City and Guilds 2377-77 qualification, which is based on the IET Code of Practice 5th Edition. This open-book exam assesses a candidate’s ability to apply the code’s guidance in real testing scenarios. The Gov.uk guidance on electrical safety in the workplace outlines how employers should approach their legal duties under health and safety legislation, and it is worth reading before setting up any formal testing programme.g electrical risks in the workplace, and their resources are a useful starting point for any business developing or reviewing its electrical safety policy. Guidance is available directly from the Health and Safety Executive’s electrical safety pages.
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What a Good Score on the PAT Test Really Means for Electrical Safety
Understanding what constitutes a good score on the PAT test goes beyond memorising a handful of numbers. It is about recognising that PAT testing exists to protect people, and that every reading, whether it is an earth continuity figure of 0.05Ω or an insulation resistance result of 300MΩ, tells part of a larger safety story. A pass is not simply a bureaucratic tick-box; it is evidence that an appliance has been checked against established safety criteria and found to pose no unacceptable risk.
It is also worth remembering that the visual inspection component of PAT testing catches up to 95% of appliance failures before any electrical test is even run. Frayed cables, damaged plugs, cracked casings, and signs of burning are all caught at this stage, meaning the numerical readings that follow are only one layer of a multi-stage process. Taking the visual inspection seriously is just as important as understanding whether your ohm reading is above or below the acceptable threshold.
For anyone managing PAT testing programmes across multiple sites or appliance types, investing in proper training and calibrated equipment pays dividends. Misinterpreting a result, such as treating a reading in milliohms as if it were in ohms, can lead to either unnecessary failures or, worse, passing equipment that should be removed from service.
What Is a Good Score on the PAT Test: Frequently Asked Questions
A PAT test does not produce a single score but rather a series of individual readings from different tests, including earth continuity, insulation resistance, and leakage current. Each reading is assessed against its own pass/fail threshold as defined by the IET Code of Practice. For a comprehensive overview, the Wikipedia page on portable appliance testing offers a useful introduction to the process and its background.
For Class I appliances tested at 500V DC, the minimum acceptable insulation resistance is 1MΩ; for Class II appliances, the minimum rises to 2MΩ. Any reading below these thresholds is classified as a fail, and the appliance should be removed from service immediately.
The earth continuity resistance must be below (0.1 + R) ohms, where R is the calculated resistance of the supply cable. For a short-lead appliance, this generally means a reading below 0.1Ω is required to pass.
Yes, a higher insulation resistance reading is always preferable as it indicates less electrical leakage through the insulation. A result of 450MΩ, for instance, reflects excellent insulation health and is significantly above the minimum threshold of 1MΩ.
Under the IET Code of Practice 5th Edition, borderline earth continuity readings within the tolerance of the test instrument should not automatically be recorded as a fail. For older appliances, readings slightly above the standard limit may be considered acceptable provided the increase is not due to deterioration.
No, Class II (double-insulated) appliances do not have an earth conductor, so the earth continuity test is not applicable. They are subject to insulation resistance testing and a thorough visual inspection instead.
The IET Code of Practice 5th Edition recommends a maximum leakage current of 5mA for both Class I and Class II appliances. This limit was increased from the previous edition to avoid unnecessarily failing equipment with slightly elevated but safe leakage levels.
Yes, a formal visual inspection is the first stage of the PAT testing process and can identify up to 95% of appliance faults. Visible damage such as frayed cables, cracked plugs, or burn marks would cause an appliance to fail before any electrical readings are taken.
There is no fixed legal frequency; the recommended interval depends on the type of equipment, its environment, and the level of risk. The HSE and IET Code of Practice both provide guidance on appropriate testing frequencies, ranging from three months for high-risk environments to several years for low-risk office equipment.
No, there is no legal requirement for a PAT tester to be a qualified electrician. The Electricity at Work Regulations 1989 require only that the person is competent, and in practice this means holding relevant training such as the City and Guilds 2377-77 qualification. Further guidance on workplace electrical safety obligations is available via HSE’s electricity at work pages.
A reading of 0.00Ω represents a theoretically perfect earth connection with no measurable resistance. In practice, most appliances return readings slightly above this due to cable length and connection resistance, but 0.00Ω is still a valid and excellent result.
A failed appliance should be labelled clearly, removed from service, and either repaired by a competent person or safely disposed of. It should not be returned to use until it has been retested and confirmed as safe.
No; whilst 500V DC is standard for most Class I appliances, IT equipment containing surge protection devices or voltage-limiting components should be tested at 250V DC to avoid triggering the protection circuitry and producing a misleading fail result.
Yes, most modern PAT testers allow the user to select between Class I and Class II testing modes, adjusting the test procedure and applicable limits accordingly. Advanced instruments will display detailed readings in ohms and megaohms, whereas simpler pass/fail devices indicate only the final outcome.