Our methodology
We don't test generators hands-on. We compare them on verifiable data, with the same method for every model. This page explains how, and what our scores don't tell you.
1. Selection
Our catalogue covers 174 portable generators (inverter, gas open frame, dual fuel and tri fuel) sold and in stock on Amazon.com at the time of our check (November 2026). We leave out battery power stations, home standby units, parts and accessories. A model that is no longer available is removed from the rankings.
2. The data
Each spec is cross-checked against the manufacturer's official US product page, spec sheet or manual. Amazon listings, often incomplete or inflated (starting watts sold as running watts), are only used for availability and typical price. When a manufacturer doesn't publish a spec, we mark it "not published" instead of guessing, and the review page says so.
3. The six criteria
| Criterion | What we measure | Weight |
|---|---|---|
| Power | Running (continuous) watts on gasoline | 20% |
| Runtime | Hours on a full tank at half load (estimated from the quarter-load figure when only that one is published) | 15% |
| Noise | Manufacturer noise rating in dB(A), lower is better | 15% |
| Features | Start type, CO shutoff sensor, inverter power, propane or natural gas, 240 V transfer-switch outlet, RV outlet, parallel capability, USB, warranty length | 15% |
| Portability | Running watts per pound (W/lb) | 10% |
| Watts per dollar | Running watts you get per dollar, at the typical price | 25% |
4. How scores are calculated
Scores are relative: on each criterion, a model is ranked among all the others, and its position is mapped to a 4-to-10 scale. The last model in the catalogue isn't a bad product; it just ranks lower on that criterion. When a manufacturer doesn't publish a spec (often the noise level on open frames), the criterion gets 5/10: we'd rather penalize missing information than ignore it.
Inverters and open frames are scored on the same scale: inverters tend to win on noise and portability, open frames on power and watts per dollar. That is why we also publish rankings by type and by use.
5. Prices
We show typical price ranges observed during our check, never an exact price: prices change often on Amazon. The price that applies is the one shown on Amazon at the time of purchase.
6. Limits
- Our scores don't measure long-term reliability, ease of starting in the cold, customer service quality or real-world noise.
- Noise figures and runtimes come from the manufacturers, measured under their own conditions (usually 23 feet and a light load for noise).
- The "will it run?" tables on review pages use typical appliance wattages: check the labels of your own appliances.
- A highly rated model may not fit your use: that's why we publish rankings by use case.
7. How we make money
As an Amazon Associate we earn from qualifying purchases. When you buy after clicking one of our links, we may earn a commission at no extra cost to you. No brand pays to appear in the rankings or to improve its position.