Frequently asked questions

Multiply your room's square footage by 10 watts, then adjust for insulation (0.8 to 1.5) and ceiling height (your height divided by 8). A 150 sq ft bedroom needs about 1,500 W. Use the calculator.

About 150 sq ft in an average heated room — 188 sq ft if it is well insulated, 120 in a drafty one, and about 100 in an unheated garage. The full table.

5,118 BTU per hour. One watt is 3.412142 BTU/h. Any 1,500 W heater advertising substantially more than 5,120 BTU/h is not quoting heat output.

No. A 1,500 W heater covers roughly 150 sq ft. A 1,500 sq ft house would need about 15,000 W — ten heaters, and far more current than a residential panel supplies to general-purpose circuits. Why.

Yes, proportionally. The square-foot rule assumes an 8-foot ceiling, so a 12-foot ceiling means multiplying the wattage by 1.5. It is the most common reason a correctly sized heater still underperforms.

A 1,500 W heater costs about 27.5 cents an hour at the U.S. average residential rate of 18.34¢/kWh. The formula is kilowatts × hours × your rate. Calculate yours.

About $198 a month for a 1,500 W unit at full output and the U.S. average rate. Continuous running usually means the heater is under-sized for the room rather than that continuous running is necessary. The monthly table.

There isn't one. Every electric resistance heater is about 100% efficient, so at the same wattage they all cost the same. Savings come from lower wattage, an accurate thermostat and less runtime. The full correction.

Only if you turn the central system down and heat one room. Per unit of heat, natural gas usually costs two to five times less than electric resistance, so the saving comes from heating less space. The per-BTU comparison.

Not per kilowatt-hour — all electric heaters are about 100% efficient. They can consume less because radiant heat makes you comfortable without raising the whole room's air temperature, so you may run them lower or for less time.

The U.S. Fire Administration advises turning space heaters off when you go to bed. A unit with a programmable timer that warms the room and then shuts itself off is the practical alternative. The data behind that guidance.

An annual average of 1,100 portable heater fires in residential buildings, causing 65 deaths, 150 injuries and $51 million in property loss (U.S. Fire Administration, 2017–2019). The full figures.

You should not. A 1,500 W heater draws 12.5 A continuously, which exceeds most household cords' ratings and adds two connectors that heat under sustained load. Why the connectors are the problem.

It will run without tripping, but 12.5 A exceeds the 12 A continuous limit a 15 A circuit gets under the 125% sizing rule. Do not share that circuit with other significant loads. The arithmetic.

Both are OSHA-recognized testing laboratories, and for a portable room heater both test to the same standard, UL 1278. Neither mark is superior to the other. How to verify a listing.

Three feet, in every direction. The leading factor contributing to ignition in residential heating fires is a heat source too close to combustibles, and no safety feature on any heater prevents that.

Neither in general. Infrared warms you and nearby surfaces almost instantly and suits large, drafty or high-ceilinged spaces. Ceramic warms the air evenly and suits enclosed rooms. The comparison.

An oil-filled radiator or a micathermic panel — neither has a fan. Every ceramic and fan-forced heater makes noise by design, because moving air is how it distributes heat. Quiet picks.

Not for heat. Every plug-in heater is capped at 1,500 W and costs the same per hour. A premium price buys control precision, build quality, quietness, warranty and sometimes a second appliance — never more warmth.

For an actual garage, a hardwired 240 V unit heater — a two-car garage needs 6,000–9,000 W and an outlet delivers 1,500. For spot heating at a bench, a radiant infrared unit. Why.

No, and every page says so. We compile published manufacturer specifications, compute the electrical load, room coverage and running cost from the rated wattage, and check the safety listing. The full method.

A numeric score implies an evaluation. We have not evaluated these units in a room, so a score would be a number we made up. The computed figures and the explicit 'not for' paragraph carry the judgment instead.

Because we never write a price into a page. Prices render from a live data layer with a check date attached, and that service is not yet provisioned for this site — so rather than show you a number we cannot date, we link you to the listing.

Affiliate commission on links to Amazon, at no extra cost to you. No sponsored placements, no paid rankings, no free products. Picks are selected before links are attached. Full disclosure.