Roundup · Sunroom
A glass room loses heat the way an uninsulated one does. The arithmetic says a single plug-in heater runs out at about 100 square feet.
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A sunroom needs about 15 watts per square foot, not the usual 10, because it is mostly glazing and usually outside the main heating system. At the 1,500 W plug-in ceiling that is roughly 100 square feet. Above that, one heater cannot keep up and radiant heat aimed at people beats warming all the air.
This site's standard rule is 10 watts per square foot, for a room with average insulation and an 8-foot ceiling. It carries two published corrections: multiply by 1.25 for a drafty room and by 1.5 for an unheated one. A sunroom is the clearest case in the house for the second correction and often deserves it twice over.
Two things make it different from the room next door. It is glazed on two or three sides, and glazing loses heat far faster than an insulated wall does. And it is usually a later addition that the house's heating system was never extended into — which is exactly what "unheated envelope" means. Neither of those is a defect; they are what makes the room pleasant in April. They are also why it is unusable in January without help.
| Room size | Watts needed | BTU/h | Plug-in heaters |
|---|---|---|---|
| 100 sq ft | 1,500 W | 5,118 | 1 |
| 150 sq ft | 2,250 W | 7,677 | 2 (different circuits) |
| 200 sq ft | 3,000 W | 10,236 | 2 (different circuits) |
Computed as square feet x 10 W x insulation factor x (ceiling / 8 ft), for an unheated space (garage, unfinished basement) — 15 W/sq ft, 8 ft ceiling. Heater count assumes the 1,500 W plug-in ceiling.
That table has the unheated correction already applied, which is why the wattages are higher than the ones on the rest of this site. Read your sunroom's floor area across and the figure you get is what the room actually wants.
In a well-sealed room, a convection heater warms the air and the air stays put long enough to warm you. In a sunroom, the air is being cooled continuously by several square feet of cold glass, so heating all of it is a treadmill — you are paying to warm air that is losing its heat through the windows as fast as you add it.
Radiant heat skips the air. An infrared heater warms the people and surfaces in its line of sight directly, so the glass can keep doing what glass does and you are still warm. That is the same reasoning that makes infrared the right answer in a garage, applied to a milder version of the same problem. The trade-off is the usual one for radiant: it warms what it can see, so placement matters and stepping out of its path ends the effect. Convection versus radiant, in full.
Sunrooms tend to be furnished densely — chairs, plants, a table — on a tile or stone floor, with less clear space than the three feet of clearance a portable heater wants on every side. A wall-mounted unit removes the floor-space problem, the tipping problem and the cord-routing problem in one decision, and in a room with a lot of glass it also frees up the wall area that is not window.
The obvious caveat: mounting is a drill and a decision, and in a rented property it is usually not permitted. If that rules it out, the portable picks below are ordered to be useful anyway.
| Wattage | Per hour | 4 h | 8 h |
|---|---|---|---|
| 1,500 W | 27.5¢ | $1.10 | $2.20 |
Computed at 18.34¢/kWh — the U.S. residential average for June 2026 (EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026). Your rate is on your own bill; substitute it and the arithmetic still holds. Figures assume full output for the whole period.
A single heater at full output is about 27.5 cents an hour, or $2.20 for an eight-hour day. The thing to notice for a sunroom specifically is that a heater in an under-sized room never cycles off — so unlike a correctly sized heater in a sealed room, you should expect to pay the full-output figure for every hour it is on rather than some fraction of it. Two heaters on two circuits doubles that.
The rate behind every figure on this site
18.34¢per kilowatt-hour
U.S. residential average for June 2026. EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026.
This is the most recent month EIA has published. Residential rates move seasonally and vary enormously by state — from roughly a dime per kilowatt-hour in parts of the South to more than 40¢ in Hawaii — so treat it as a national reference point, not as your rate.
And if you are thinking of two heaters: they need to be on different circuits. Two 1,500 W units draw 25 A between them, which no residential 15 or 20 A circuit will carry. The circuit arithmetic.
Radiant first, because that is the reasoning above; then the wall-mounted option; then a convection unit for a small, well-sealed sunroom; then the silent choice for a room you sit and read in.
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 |  Dr Infrared DR-968The one listing in this category that publishes its amp draw and its noise level, which is exactly the arithmetic everyone else leaves you to do — 12.5 A and 39 dB, both stated. | The published numbers | 150 sq ft | 12.5 A | $112.99 · Check on Amazon−10% |
| 2 |  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 |
| 3 |  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 |
| 4 |  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 | $162.28 · 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.
Top pick · The published numbers
The one listing in this category that publishes its amp draw and its noise level, which is exactly the arithmetic everyone else leaves you to do — 12.5 A and 39 dB, both stated.
| Published specification | |
|---|---|
| Rated power | 1,500 W at 120 V |
| Current draw | 12.5 A (published) |
| Noise | 39 dB (published) |
| Element | Infrared quartz tube plus PTC |
| Thermostat | Electronic, 50–85°F |
| Other | 12-hour auto-off timer, IR remote, caster wheels, 19 lb |
| 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 cabinet's rating plate for the UL or ETL mark. |
Who it is for
A reader who wants to compute the load rather than trust a claim: the published amp draw and decibel figure make it the easiest unit on this site to check.
What it is not for
A 15 A circuit shared with anything else, and not a small room where a 19 lb cabinet on wheels is in the way.
2 · Getting the heater off the floor
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.
| 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.
Sources for this entry
3 · A whole living room
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.
| 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.
4 · Silence, and a bedroom
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.
| 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.
And what we did not do: we have not tested these units, owned them, measured them or run them in a room. Everything above is compiled from published manufacturer specifications and live retail listings, with the electrical load, room coverage and running cost computed by us from the published wattage. The full method.
Every roundup on this site names something to skip. It costs us nothing to publish and it is the fastest way to tell whether a buying guide was written for you or for its commission.
One 1,500 W heater for a sunroom much over 100 sq ft
Here is the arithmetic the listings never do. The standard rule is 10 W per square foot; an unheated envelope needs 1.5x that, so a sunroom wants roughly 15 W per square foot. At 1,500 W — the ceiling for any U.S. outlet — that is 100 square feet. A 150 sq ft sunroom wants about 2,250 W and a 200 sq ft one about 3,000 W. A single heater in those rooms is not undersized by a little; it is delivering two-thirds or half of what the space needs, and it will run continuously without ever cycling.
A patio or outdoor heater brought inside for the job
Outdoor patio heaters are a different product class with different safety assumptions, and the propane ones are combustion appliances that have no business in an enclosed room — a sunroom is enclosed, whatever it feels like. Everything on this site is electric and indoor-rated. If the space is genuinely unenclosed, it is outside this site's scope and the honest answer is that no indoor heater is designed for it.
About 15 watts per square foot — the standard 10 W/sq ft rule with the 1.5x unheated-envelope correction applied, because a sunroom is mostly glazing and usually outside the main heating system. A 100 sq ft sunroom wants about 1,500 W, a 150 sq ft one about 2,250 W.
Up to about 100 square feet, yes. Above that a single 1,500 W heater is delivering well under what the room needs and will run continuously without cycling. The options then are a second heater on a separate circuit, radiant heat aimed at people rather than the room, or treating it as a three-season space.
Infrared or radiant, in most cases. A sunroom's air is cooled continuously by cold glass, so warming all of it is an uphill battle, while radiant heat warms people and surfaces directly and is unaffected by the air temperature. A convection heater suits only a small, well-sealed sunroom.
They cost the same per hour as any other electric heater — about 27.5 cents at 1,500 W — but they run for more of those hours. A heater in an under-sized room never reaches its set point, so it does not cycle off, and you should budget for full output the whole time it is on.
No. Outdoor patio heaters are a different product class, and propane models are combustion appliances that should never run in an enclosed space — and a sunroom is enclosed. Everything on this site is electric and indoor-rated.
The four units that get closest to a 300 sq ft room — and the two-heater arithmetic nobody publishes.
Heats you, not the air — which is why it wins in drafty rooms and loses behind the sofa.
Where the 10 W/sq ft rule comes from, when it breaks, and the exact watt-to-BTU conversion.
Mounting deletes tipping, floor clearance, cord routing and child reach. Plug-in panels and one hardwired unit.
Heating the air versus heating the things in it — the distinction under every other comparison.
12.5 A against a 12 A continuous limit — the arithmetic nobody publishes, and what to do about it.