How to choose a space heater

Why the order is the whole technique

Most heater shopping starts at step six — a shape that looks right — and works backwards, which is how people end up with a tower heater that cannot warm the room it was bought for. The six decisions below are not equally important and they are not independent. Each one narrows what the next can be, and the first narrows it hardest.

None of this is about finding a better heater. Every plug-in heater sold in the United States is capped at 1,500 W, which means they all produce the same heat and cost the same per hour to run. What varies is fit — and fit is a property of your room, not of the product.

1. Size the room, in watts

The rule is 10 watts per square foot for a room with average insulation and an 8-foot ceiling. Multiply by 1.25 for a drafty or single-glazed room, by 1.5 for a space outside the heated envelope — a garage, an uninsulated basement, a sunroom — and by the ceiling height over eight feet, because heating is a volume problem that a floor-area rule hides.

Then compare the answer with 1,500 W, because that is the ceiling and it is not negotiable: a 120 V, 15 A branch circuit may not carry more as a continuous load. If your room needs more than about 1,500 W, no plug-in heater will heat it, and the choice is a 240 V hardwired unit, more than one circuit, or accepting a supplement to your central heat rather than a replacement for it. The sizing calculator does this for your room; the rule and its corrections explains where the 10 comes from.

2. Decide whether you are heating the room or the person

This is the decision with the largest spread in cost and the one most buyers never consider. If the complaint is "my legs are cold at my desk for six hours a day", heating 3,000 cubic feet of air to fix it is the expensive way round.

A tenth of the running cost and a tenth of the current, for the only outcome you asked for. The trade is real and absolute: a 150 W panel will not raise a room's air temperature at all, so this only works where the problem is a stationary person rather than a cold room. Desk and under-desk heaters is the full version of that argument.

3. Choose the type, which is really a noise decision

At equal wattage the types produce identical heat and cost identical money. What differs is how fast the heat arrives, where it goes, and whether you can hear it — and the single cleanest test is whether the unit has a fan.

Two rules fall out of that table. If the heater is going in a bedroom, buy a fanless type — the noise is the thing that makes people stop using a heater, and it is the one property you cannot fix later. If the room is leaky or you only occupy it for twenty minutes at a time, buy radiant — convection spends its first twenty minutes heating air that is on its way outside.

4. Insist on a thermostat with numbers on it

Once the room is sized and the type is chosen, the thermostat is the only remaining lever on your bill, because the only variable left is hours. A heater you can set to 68°F cycles off and stays off. A dial marked low-to-high gets set too high, overshoots, and gets switched off by hand an hour later than it should have been.

Only 7 of the 29 purchasable heaters we track publish a thermostat range in degrees. That is the single most useful filter in this entire guide, and it is nearly free to apply: if the listing cannot tell you what temperatures the thermostat covers, the thermostat is a knob. A published low wattage is the companion specification — "three heat settings" with no wattages gives you one costable number out of three, while a published 750 W step is exactly half the running cost of 1,500 W with no efficiency penalty.

A timer is the third control worth paying for, and it is the honest answer to overnight running: the U.S. Fire Administration's guidance is to switch a heater off when you go to bed, and a unit that warms the room and then shuts itself off lets you comply without being cold. Running a heater overnight has the arithmetic — two timed hours at bedtime is about 55 cents against $2.20 for a full night.

5. Check the cutoffs, and the lock if it is relevant

Two cutoffs are close to universal in this registry and both should be published, not assumed: an overheat cutoff that opens when airflow is restricted, and a tip-over switch that kills the element when the unit is not upright. How each one works.

• A child lock is rare and it is not the same thing as a tip-over switch. If a toddler can reach the controls, this is the specification to filter on — and most listings do not have it. Nursery picks and pet-safe picks are built on exactly this.
• Cool-touch housings are a ceramic-type advantage, because a self-limiting PTC element makes a genuinely cool exterior easier to achieve. A radiator or a mica panel is hot by design — that is not a defect, it is how it radiates.
• A named safety listing beats a reassuring photograph. UL and ETL both test portable room heaters to the same standard, UL 1278, so neither mark is superior and a unit with either is listed. What the marks mean.
• Nothing goes on an extension cord or a power strip. A 1,500 W heater is a 12.5 A continuous load, and this is the most common way a heater starts a fire. Why cords fail.

6. Only now choose a shape

Shape is last because it is the constraint that is easiest to satisfy once everything above is fixed, and the one most likely to override a correct decision if you let it go first.

• Tower — a tall footprint in little floor area, oscillating, and the shape most likely to be knocked over by a dog or a vacuum cleaner. Tower picks.
• Tabletop — fits a desk or a shelf, puts the cord where it gets stepped on.
• Radiator on castors — heavy, silent, steady, and it stays where you put it. Oil-filled picks.
• Wall-mounted — removes the tip-over failure mode entirely rather than mitigating it, and frees the floor. It is a mounting job. Wall-mounted picks.
• Hardwired 240 V — the only route past 1,500 W, and an electrician's job with a permit attached. 240 V unit heaters.

And check the circuit the shape implies. A 1,500 W heater is 12.5 A against the 12 A a 15 A circuit may carry continuously, which means one heater per circuit and nothing else significant on it:

What not to decide on

• Brand. What separates the brands in our registry is how much each one publishes, not how warm it gets — the brand disclosure table is the honest version of a brand ranking.
• BTU claims. 1 W is 3.412142 BTU/h exactly, so a 1,500 W heater is 5,118 BTU/h and nothing can exceed it. A plug-in heater advertising 10,000 BTU is the clearest signal in this category that nothing else on the listing is reliable either.
• Coverage claims. Most are 10 W per square foot computed backwards, which is correct for a room inside the house and optimistic for anywhere else. Size the room yourself and compare.
• "Energy efficient" and "eco". Every electric resistance heater is essentially 100% efficient, which is why there is no ENERGY STAR category for them. What genuinely lowers consumption is a lower wattage setting, an accurate thermostat and fewer hours — the honest version.
• Price as a proxy for heat. The cheapest heater in our registry and the most expensive one both produce 5,118 BTU/h for about 27.5 cents an hour. The premium buys control, build, silence and warranty. It does not buy warmth.

Five answers, one per decision path

These are not ranked against each other, because they answer different sets of answers to the six questions. Find the line that describes your room and the pick is the one beside it.

Quick picks

Ranked for fit, not for hype. Coverage and current draw are computed from each unit’s published wattage. Tap a row for the full write-up, or go straight to the listing.

#	Product	Best for	Covers	Draw	Price
1	Dreo Solaris 718The rare heater whose published coverage claim survives the arithmetic: 1,500 W is a genuine 300 sq ft at 10 W/sq ft, and Dreo publishes that number rather than implying more.	A whole living room	150 sq ft	12.5 A	$129.99 · Check on Amazon
2	De'Longhi TRD40615TNo fan, so no noise and no moving dust — and the sealed oil keeps radiating after the element cuts out, which is why an oil-filled unit feels steadier than a ceramic one at the same wattage.	Silence, and a bedroom	150 sq ft	12.5 A	$159.95 · Check on Amazon
3	Heat Storm HS-1500-PHXWall-mounted, which removes the entire tip-over failure mode rather than mitigating it — and Wi-Fi scheduling means it can heat a bathroom before you get in it.	Getting the heater off the floor	150 sq ft	12.5 A	$149.99 · Check on Amazon
4	Cozy Legs CLA 150 W radiant panel that does one job — warm the legs in a footwell — and is the only heater in this registry whose maker publishes a zero-clearance safety listing on its own page.	The cheapest real under-desk panel	15 sq ft	1.3 A	$49.99 · Check on Amazon
5	Comfort Zone CZ230ER7,500 W with a digital thermostat, a remote and a 12-hour timer for less than the 5,000 W units cost — and its manual specifies the 40 A breaker and 8 AWG wire the load actually needs.	A cold two-car garage	750 sq ft	31.3 A	$144.97 · Check on Amazon

Coverage computed at 10 W/sq ft, average insulation, 8 ft ceiling. Draw computed as watts ÷ volts. Neither figure is a manufacturer claim.

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Top pick · A whole living room

Dreo Solaris 718 Oscillating Tower Heater (30 in)

The rare heater whose published coverage claim survives the arithmetic: 1,500 W is a genuine 300 sq ft at 10 W/sq ft, and Dreo publishes that number rather than implying more.

Rated power

1,500 W

Covers (computed)

150 sq ft

Draw (computed)

12.5 A at 120 V

Cost per hour

27.5¢

Coverage at 10 W/sq ft, average insulation, 8 ft ceiling = 5,118 BTU/h. Cost at 18.34¢/kWh; an eight-hour night at full output is $2.20. Exceeds the 12 A continuous limit of a 15 A circuit — check what else shares the breaker.

What works

• A digital thermostat with numbers on it — you can set 68°F rather than guess at a dial
• The published 300 sq ft claim matches the standard sizing rule instead of exceeding it
• 8 lb and 8 inches square: it moves room to room without a project

What does not

• 1,500 W is 1,500 W — nothing here heats faster than any other 1,500 W heater
• Dreo does not publish a noise figure in decibels on the product page
• Tall and narrow, which is a tipping profile: the tip-over cutoff matters more here

Published specification
Rated power	1,500 W at 120 V
Maker's coverage claim	300 sq ft
Thermostat	41–95°F digital, 1°F increments
Oscillation	30° / 60° / 90° / 120°
Dimensions	7.9" D x 7.9" W x 29.7" H, 8 lb
Safety	Tip-over cutoff, overheat cutoff, child lock, thermal cutoff
Heat type	Ceramic (PTC)
Maker’s coverage claim	300 sq ft
Safety listing	ETL listed (stated by Dreo on the product page)

Who it is for

A living room, bedroom or den at or under 300 sq ft with average insulation and an 8-foot ceiling, where you want to set a temperature and stop thinking about it.

What it is not for

A garage, an uninsulated basement, or anything over about 300 sq ft. It is not under-powered — 1,500 W is the plug-in ceiling — the room is simply too big for one outlet.

$129.99 · Check on Amazon

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Sources for this entry

• Amazon listing — published title, features and availability
• Dreo — Tower Heater 718 product page (published specifications)

2 · Silence, and a bedroom

De'Longhi TRD40615T Oil-Filled Radiator Heater

No fan, so no noise and no moving dust — and the sealed oil keeps radiating after the element cuts out, which is why an oil-filled unit feels steadier than a ceramic one at the same wattage.

Rated power

1,500 W

Covers (computed)

150 sq ft

Draw (computed)

12.5 A at 120 V

Cost per hour

27.5¢

Coverage at 10 W/sq ft, average insulation, 8 ft ceiling = 5,118 BTU/h. Cost at 18.34¢/kWh; an eight-hour night at full output is $2.20. Exceeds the 12 A continuous limit of a 15 A circuit — check what else shares the breaker.

What works

• Genuinely silent: there is no fan to hear at 3 a.m.
• The oil holds heat, so the room temperature swings less between thermostat cycles
• Nothing blows air, so nothing stirs up dust in a bedroom

What does not

• Slow. It takes 20–30 minutes to feel like it is doing anything
• Heavy — the wheels are not a courtesy, they are a requirement
• The surface gets genuinely hot; this is a radiator, not a cool-touch case

Published specification
Rated power	1,500 W at 120 V
Controls	Mechanical, with a programmable 24-hour timer
Fluid	Permanently sealed diathermic oil — never needs refilling
Maker's claim	Up to 75% more radiant surface area
Mobility	Front and rear handles, snap-on wheels
Heat type	Oil-filled
Maker’s coverage claim	None published — the coverage figure above is ours
Safety listing	No listing mark published in the listing text; verify the UL or ETL mark on the rating plate.

Who it is for

A bedroom, a nursery at a safe distance, or anywhere the fan noise of a ceramic heater is the actual problem you are trying to solve.

What it is not for

Fast heat, and not a room you only occupy for twenty minutes. It also should never be tucked beside a bed or curtain — hot surface, 3-foot rule.

$159.95 · Check on Amazon

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Sources for this entry

• Amazon listing — published title, wattage, timer and availability
• De'Longhi — oil-filled radiator range

3 · Getting the heater off the floor

Heat Storm HS-1500-PHX-WIFI Wall-Mounted Infrared Heater

Wall-mounted, which removes the entire tip-over failure mode rather than mitigating it — and Wi-Fi scheduling means it can heat a bathroom before you get in it.

Rated power

1,500 W

Covers (computed)

150 sq ft

Draw (computed)

12.5 A at 120 V

Cost per hour

27.5¢

Coverage at 10 W/sq ft, average insulation, 8 ft ceiling = 5,118 BTU/h. Cost at 18.34¢/kWh; an eight-hour night at full output is $2.20. Exceeds the 12 A continuous limit of a 15 A circuit — check what else shares the breaker.

What works

• On a wall it cannot be tipped, and it cannot be crowded by a curtain that moved
• Scheduling from the app is the practical answer to bathroom and workshop use
• The published 5,200 BTU/h figure matches 1,500 W exactly — no inflated claim

What does not

• It is a mounting job, not an unbox-and-plug — and it needs an outlet where you mount it
• Wi-Fi adds a failure mode a knob does not have
• Wall-mounted radiant heat is directional; you feel it where it points

Published specification
Rated power	1,500 W at 120 V
Published output	5,200 BTU/h
Mounting	Wall-mounted
Control	Wi-Fi app, remote scheduling
Element	Infrared quartz
Heat type	Infrared quartz
Maker’s coverage claim	None published — the coverage figure above is ours
Safety listing	No listing mark published in the listing text; check the rating plate for the UL or ETL mark.

Who it is for

A bathroom, a small bedroom, a workshop corner — anywhere floor space is gone and a heater on the ground is a hazard.

What it is not for

Renters who cannot drill, and rooms where you want the heater to move with you.

$149.99 · Check on Amazon

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Sources for this entry

• Amazon listing — published wattage, 5,200 BTU/h, wall mounting, Wi-Fi

4 · The cheapest real under-desk panel

Cozy Products Cozy Legs CL Flat Panel Heater

A 150 W radiant panel that does one job — warm the legs in a footwell — and is the only heater in this registry whose maker publishes a zero-clearance safety listing on its own page.

Rated power

150 W

Covers (computed)

15 sq ft

Draw (computed)

1.3 A at 120 V

Cost per hour

2.8¢

Coverage at 10 W/sq ft, average insulation, 8 ft ceiling = 512 BTU/h. Cost at 18.34¢/kWh; an eight-hour night at full output is $0.22. Fits a 15 A circuit as a continuous load.

What works

• 150 W is 1.25 A — about a tenth of a 1,500 W room heater, so it will not trouble a desk circuit already carrying a computer and two monitors
• Silent by construction: a radiant panel has no fan and no moving parts at all
• The maker publishes an ETL zero-clearance listing — a rarity in this registry, and the reason the panel can sit flat against a desk modesty board or a wall

What does not

• No set-point. The thermostat is built in and no range is published, so there is nothing to dial and no timer — it runs until the in-cord switch goes off
• Cozy Products publishes no coverage figure, no warranty terms and no panel dimensions on the product page, so none of the three can be checked
• 150 W warms your legs and nothing else. It is not a small room heater and it will not raise the air temperature of an office

Published specification
Rated power	150 W at 120 V, 60 Hz (Cozy Products' published figures)
Current draw	1.25 A (150 ÷ 120) — our figure. Cozy Products' page prints 1.3 A, which is the same draw rounded
Element	Radiant panel — no fan, no moving parts
Thermostat	Built-in; Cozy Products publishes no set-point range, so there is no temperature to choose
Controls	An in-cord roller switch
Size	Cozy Products publishes the shipping box at 25 x 20 x 2 inches and the weight at 8 lb, but not the panel's own dimensions — so we do not print a panel size
Surface temperature	Approximately 130°F (Cozy Products' published figure)
Safety	ETL Certified Zero-Clearance — no clearance required, which the maker states on its own page
Heat type	Radiant panel
Maker’s coverage claim	None published — the coverage figure above is ours
Safety listing	Cozy Products publishes an ETL Certified Zero-Clearance rating on its own product page, which is why the panel may sit against a wall or other combustible surface.

Who it is for

A footwell where the complaint is cold legs, the circuit is already busy, and you want the lowest-draw honest answer rather than a 1,500 W heater in a small box.

What it is not for

Heating a room, or anywhere you need the heater to switch itself off. Without a timer or a set-point it is on until you switch it off at the cord, which makes the [unattended-heater guidance](/safety/overnight) matter more, not less.

$49.99 · Check on Amazon

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Sources for this entry

• Amazon listing — published 150 W flat panel heater, model CL
• Cozy Products — Cozy Legs product page, SKU CL-RETAIL (150 W, 1.3 A, 120 V/60 Hz, built-in thermostat, in-cord roller switch, approximately 130°F operating temperature, no clearance required, ETL Certified Zero-Clearance, 8 lb)
• Cozy Products — safety information (ETL Certified and Zero-Clearance explained)

5 · A cold two-car garage

Comfort Zone CZ230ER Digital Hard-Wired Ceiling-Mount Garage Heater

7,500 W with a digital thermostat, a remote and a 12-hour timer for less than the 5,000 W units cost — and its manual specifies the 40 A breaker and 8 AWG wire the load actually needs.

Rated power

7,500 W / 6,250 W low

Covers (computed)

750 sq ft

Draw (computed)

31.3 A at 240 V

Cost per hour

137.6¢

Coverage at 10 W/sq ft, average insulation, 8 ft ceiling = 25,591 BTU/h. Cost at 18.34¢/kWh; an eight-hour night at full output is $11.00. Hardwired 240 V: this is an electrician's installation, not a plug-in appliance.

What works

• The most heat here by half again, and it costs less than either 5,000 W pick
• Its manual gets the hard part right: 31.3 A of draw, 40 A of breaker, 8 AWG of wire, stated as three separate specifications
• A 12-hour timer with auto shut-off, which on a load this size is the feature that protects the bill
• Fan-only mode makes it useful in summer, which no other pick here offers

What does not

• 40 A of two-pole capacity is a serious allocation — this is the pick most likely to run into a full panel
• $1.38 an hour at full output, the highest running cost on this site
• No certification mark published anywhere we could find, in the listing or the manual
• Sold under two near-identical listings whose prices and stock move independently — on 2026-10-17 the CZ230ER listing was the cheaper one and in stock while the CZ230ERBK one was a few dollars more on a two-to-four-week lead time. Open both
• The digital thermostat has no published set-point range, so the LED shows the room temperature rather than a target you chose

Published specification
Rated power	7,500 W high (default) / 6,250 W low at 208–240 V
Current draw (maker's figures)	31.3 A high / 26 A low — matches 7,500 ÷ 240 = 31.3 A
Recommended circuit breaker	40 A or larger, per the manual — the draw grossed up by the NEC continuous-load rule is 39.1 A
Recommended wire	8 AWG copper only, rated 167°F/75°C or larger, per the manual
Published output	25,590 BTU/h high / 21,240 BTU/h low
Horizontal air throw	18 ft (approximate), per the manual
Controls	Digital thermostat with an LED ambient-temperature display, remote, 12-hour timer with auto shut-off, fan-only mode. No set-point scale published
Weight	25–30 lb (approximate), per the manual
Warranty	One year against defects in quality or workmanship (World and Main)
Installation	Hardwired, ceiling- or wall-mounted. No plug, and extension cords are prohibited
Heat type	Fan-forced
Maker’s coverage claim	None published — the coverage figure above is ours
Safety listing	Neither the listing nor the CZ230ER Series manual names a certification mark. On a hardwired 240 V unit the rating plate is what the installer works from.

Who it is for

A two-car garage, a shop or an outbuilding of roughly 400–600 sq ft where you want it genuinely warm, and you have 40 A of two-pole space in the panel.

What it is not for

A single-car garage or a panel that is already full — 7,500 W is more heat than a small space needs and more current than a tight panel can give.

$144.97 · Check on Amazon

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Sources for this entry

• Amazon listing (the one we pin) — published 7,500 W / 240 V, fan-forced, overheat protection, digital thermostat, 12-hour timer, remote, model CZ230ER. In stock, and the cheaper of the two listings, when checked on 2026-10-17
• Second Amazon listing for the same heater — model CZ230ERBK, priced independently; a few dollars more and on a two-to-four-week lead time when checked on 2026-10-17
• CZ230ER Series manual (World and Main, comfortzoneproducts.com) — specification table: 7,500 W at 31.3 A and 25,590 BTU/h, 6,250 W at 26 A and 21,240 BTU/h, 40 A breaker, 8 AWG copper, 18 ft air throw, 25–30 lb, one-year warranty

If you remember one thing

Size the room before you look at a single product. Everything else on this page is a preference you can live with being wrong about; the sizing arithmetic is the one that decides whether the heater you buy can do the job at all. The calculator takes about thirty seconds.