HomeComparison: Seaward Primetest 250 vs Megger PAT150
Update (February 2026): This is a legacy comparison first published in 2016. Models, pricing and software options change over time, but the practical considerations discussed here (test capability, usability, lead nulling, PRCD testing and adjustable limits) are still relevant. For up-to-date buying advice, see our guide to choosing a PAT tester. If you’re new to PAT testing, our PAT testing courses cover correct test selection and interpreting readings.
The Seaward Primetest 250 and the Megger PAT150 are both small, battery-powered PAT testers designed for straightforward in-service testing. Both support the core tests typically used in portable appliance testing (earth continuity, insulation resistance, substitute leakage, polarity testing for leads, and mains-powered leakage/RCD testing where applicable).
Important: this comparison focuses on practical testing and usability in real-world PAT work, not just a spec sheet. If you’re new to PAT testing, it’s worth reading the guidance behind the test limits in the IET Code of Practice guide and our common PAT testing mistakes article (including why recording the measured readings matters, not just pass/fail).
The PAT150 is slightly larger and heavier than the Primetest 250, but there’s not much in it day-to-day. The PAT150 feels more rugged, with a thick rubberised bumper and a clever flip-over lid to protect the screen and keyboard. The Primetest is supplied with a soft carry case and has rubberised protection on the top/bottom edges, but doesn’t feel quite as “armoured” as the Megger.
Both testers offer simple automatic test routines for Class I and Class II equipment. The PAT150 has a dedicated extension/IEC lead test button, whereas the Primetest 250 uses the Class I button and auto-detects a lead. The PAT150’s buttons have a more positive feel; the Primetest buttons are rubberised and can feel a bit spongy. A small but surprisingly useful feature on the PAT150 is the ability to abort a test and return to the main screen; the Primetest has no easy “stop” once a sequence starts.
The available test options is where the biggest difference appears. Both support switching the insulation resistance test voltage from 500V to 250V for surge-protected equipment and older IT equipment. The Primetest also allows an adjustment to the leakage limit for Class I equipment in certain categories, but most other options are fixed.
The Megger PAT150 allows much more control over test settings: earth, insulation and leakage pass limits can be adjusted, along with test duration. It also includes a useful single-test mode (run one test without a full sequence), plus extra functions such as a point-to-point continuity test (useful for fixed equipment) and a SELV measurement.
Both instruments can carry out a trip time test for portable RCDs, but the approach differs. The Megger PAT150 can test PRCDs without tripping the main RCD in the distribution board, which is a genuine advantage on customer sites. With the Primetest 250, avoiding nuisance tripping usually means using an isolation transformer or finding a non-RCD protected circuit (often impractical).
One feature that’s always worth having is the ability to null the resistance of test leads. When you’re measuring very low earth continuity values, test lead resistance can materially influence the result. The PAT150 can null both the test lead and IEC lead; the Primetest 250 does not.
This also ties into correct earth continuity limits, which are 0.1Ω + R (where R is the resistance of the protective conductor in the supply cable). If you’re unsure how to allow for cable length/CSA, see our earth continuity limit guide and calculator.
Both testers run on AA batteries and both have a reputation for excellent battery life. The Megger PAT150 is also available in a rechargeable variant (PAT150R). In practical use, battery life is highly dependent on the type and duration of tests performed, but either model is suitable for full-day testing in typical workplaces.
The Seaward Primetest 250 is straightforward, reliable, and very quick to learn. If you want simplicity and you’re working to a tight budget, it has historically been a solid option.
However, when you factor in features like the no-trip PRCD test capability, point-to-point continuity, and test lead nulling, the Megger PAT150 is (in the context of this comparison) the more capable instrument for varied on-site work.
Quick comparison table
| Seaward | Megger | |
|---|---|---|
| Primetest 250 | PAT150 | |
| Price | £349+VAT (historic) | £399+VAT (historic) |
| Weight | 935g | 1,235g |
| Size (approx) | 11x26x6 cm | 15x20x8 cm |
| Earth Continuity Test | 200mA | 200mA |
| Insulation Test | 500V & 250V | 500V & 250V |
| IEC / Extension Polarity | Yes | Yes |
| Substitute Leakage Test | Yes | Yes |
| Leakage Test | Yes*1 | Yes*1 |
| Portable RCD Test | Yes*1 | Yes*1 & 2 |
| Power Socket Test | Yes | Yes |
| 3-Phase Leakage Test | Yes*3 | No |
| SELV Test | No | Yes |
| Fixed Equipment Earth Test | No | Yes |
| Adjustable Pass Limits | No | Yes |
| Test Lead Nulling | No | Yes |
| LCD Backlight | No | Yes |
| Calibration Certificate | No | Yes |
*1 - Mains supply required
*2 - No trip RCD test
*3 - Seaward 3-phase adaptor required
Choosing a PAT tester today
If you’re buying a PAT tester now, focus on the features that make testing faster, safer and easier:
- Displays readings (earth/insulation/leakage), not just pass/fail
- Correct test options (250V/500V insulation, appropriate leakage tests)
- Lead nulling (helpful when working close to the 0.1Ω + R limits)
- Useful extras if you need them (PRCD/RCD testing, point-to-point continuity)
For current models and accessories, see our PAT equipment shop. If you want hands-on training in correct test selection, interpreting results, and avoiding common errors, view our PAT testing courses.