Every space heater gets a score from 0 to 100% built from six factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Heaters are grouped by type, fan, radiator or radiant, and each group has its own price scale.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per kilowatt of heat | 25% |
| Safety | safety listing, tip-over and overheat shutoff | 25% |
| Thermostat | whether it holds a set temperature | 15% |
| Warranty | warranty length | 15% |
| Controls | eco mode, timer, remote, app | 10% |
| Low setting | how gently it can heat a small room | 10% |
Where the numbers come from
Wattage, controls, safety features, safety listing and warranty come from the maker’s product page, manual or warranty page, or the maker’s own copy on its Amazon listing. Noise and power draw measured by independent testers are shown on product pages where they’ve been published.
Why heat output isn’t scored
A plug-in electric heater turns every watt it draws into heat, so two heaters on the same setting give the same heat, whatever their element or claims about heating “faster” or “more efficiently”. Most top out at 1,500 W, the limit for a standard 15 A outlet. Wattage still goes into value, since a 500 W desk heater gives a third of the heat of a 1,500 W one.
The factors
Value is the current price divided by the heater’s highest setting in kilowatts, on a log scale for each group, so going from $40 to $20 a kilowatt counts as much as going from $100 to $50.
| Group | Scores 0 | Full marks |
|---|---|---|
| Fan heaters | $100 per kW | $20 per kW |
| Radiators | $130 per kW | $40 per kW |
| Radiant heaters | $100 per kW | $20 per kW |
Safety adds up three things:
| Feature | Share of the factor |
|---|---|
| A safety listing from a recognized lab (UL, ETL, CSA) | 40% |
| Switches off if knocked over | 30% |
| Switches off if it overheats | 30% |
A listing means a lab such as UL or Intertek (ETL) has tested the heater to the safety standard for portable heaters, UL 1278, and keeps checking the factory. Many heaters sold online don’t say whether they’re listed, so a heater whose maker publishes no listing gets no credit for it. Our safety listing study shows how many state one, by brand and price. A shutoff the maker doesn’t state either way gets half credit.
Thermostat is full marks for a heater you set to a temperature, which then turns itself up and down to hold it; 60% for an adjustable thermostat dial with no set temperature; and zero for one that only has fixed heat levels and runs until you switch it off.
Warranty: 1 year scores zero and 5 years full marks.
Controls gives a quarter each for an eco or auto mode that picks the heat level for you, a timer, a remote and a phone app. A feature the maker doesn’t state either way gets half credit.
Low setting is the lowest heat setting, which decides whether a heater can keep a small room or office comfortable without cycling between too hot and off: 1,000 W scores zero and 400 W full marks.
What isn’t scored
Noise, oscillation, size, weight, cord length and looks are listed but not scored. Independent tests are listed where they exist, but there are too few to score.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. The safety listing is the exception: a listing has to be stated to count.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.