Pulls air in at the bottom and lets it rise out the top, holding a steady background temperature.
also: panel heater, convector heater
The basics
What to know about space heaters
One room, while it runs
A space heater warms one room while it runs, and does nothing for the rest of the house. Every portable electric model works the same way. Current passes through a resistance element, the element gets hot, and that heat reaches you either as moving warm air or as infrared radiation crossing the room. Nothing burns inside, so there is no flue, no fuel and no carbon monoxide from the appliance itself. In exchange you accept a hard ceiling on output. A standard US wall outlet on a 120 volt, 15 amp circuit supports 1,500 watts of continuous heat. This is 5,118 BTU per hour, the BTU being the unit furnaces are rated in, against 40,000 for a modest gas furnace. Nothing plugged into a normal socket beats 1,500 watts, and a listing promising more describes a 240 volt appliance an electrician has to wire in.
How the heat leaves the box
How the heat leaves the box decides how the room feels. Convection warms air, which rises, circulates and lifts the whole room a few degrees over 20 to 40 minutes, then leaves with that air the moment a door opens. Radiant heat skips the air entirely and lands on skin, floors and furniture. You feel it in under a minute, but only within line of sight. Elements differ just as much. Bare nichrome coil wire glows near 1,300 degrees F and scorches the dust floating past it. This is the smell of a heater's first run each winter. Ceramic elements use a positive temperature coefficient material. That means resistance that climbs as it heats, so the element limits its own temperature and never glows. Sealed oil, quartz tubes and mica sheets hold and release that same heat on their own schedules.
Match it to how you use the room
Match the format to how you actually use the room. A Ceramic Heater makes a cold 150 square foot office usable in about five minutes, at the price of roughly 45 decibels of fan noise. An Oil-Filled Radiator needs half an hour to matter, then keeps giving heat back for 15 to 20 minutes after you switch it off. It suits a bedroom warmed before bed. Aim an Infrared Heater at a workbench, a reading chair or a garage corner, where warming all the air is hopeless and warming the person is not. A Fan-Forced Heater is the cheap, fast answer for a bathroom you stand in for ten minutes. A Micathermic Heater sits between the silent options, with no fan and no oil to preheat. If one room needs heat all day every winter, none of these is the right purchase: that job belongs to a Ductless Mini-Split, which delivers close to three units of heat per unit of electricity instead of one.
Two costs behind every one
Two costs sit behind every one of these. Money is the visible one. Electric resistance turns essentially all the electricity it draws into heat, so 1,500 watts consumes 1.5 kilowatt hours every hour at full output. At 17 cents per kilowatt hour that is about 26 cents an hour, near 2 dollars for an 8 hour evening and roughly 60 dollars across a month of daily use. Heating a whole house this way costs about three times what a heat pump costs for the same warmth. Fire is the second, and not a small risk. US fire investigators trace a large majority of home heating fire deaths to portable heaters, and the leading factor never changes: something combustible sitting too close. Keep three feet clear on every side, above and in front, counting bedding, curtains, laundry, paper, furniture and pet beds. Plug the heater straight into a wall outlet, because an extension cord, a power strip, a surge protector or an outlet adapter cannot carry 12.5 continuous amps safely, and melted cords are how these fires start.
Look for the safety mark
Judge one on evidence and controls. Look first for a UL, ETL or CSA mark, which shows the design was tested against the portable heater safety standard, since a heater with no recognizable certification mark has nothing behind its claimed cutouts. Then try the tip-over switch yourself: tilt a running unit about ten degrees and it should die before it leaves your hand. Price shows honestly in the thermostat. A bimetal dial swings 5 to 10 degrees F, so the room goes hot and then chilly. Meanwhile, a digital thermostat holds within 1 to 2 degrees and shuts the element off between cycles. This is the only real way one of these lowers a bill. Inspect the cord where it enters the housing, since 16 gauge or heavier is normal at 1,500 watts and a thin flexible lead is a warning. For a bedroom, check the stated noise figure.
Dust and attention
Keeping one alive is mostly dust and attention. Vacuum the grilles monthly through the season, because a felt of dust insulates the element, drives internal temperature up and eventually trips the thermal cutout permanently. Fifteen minutes into a run, touch the plug and the wall plate. Warm is expected, hot means a worn outlet that needs replacing before you use it for a heater again. Each autumn, run the cord through your fingers looking for stiffness, cracks or a discolored plug, and retire the heater if you find any. Above all, switch it off when you leave the room and before you sleep. No timer, no cutout and no certification mark substitutes for someone awake.
Buyer checklist
Before you buy space heaters
A major appliance must fit the space, the utilities and the service network. Running cost and repair access belong in the first comparison.
01
Measure the full installation
Include doors, handles, hoses, vents, clearance, service access and the delivery path, not only the cabinet opening.
02
Confirm every utility
Check voltage, circuit, plug, water, drain, gas and ventilation requirements against the exact model and local rules.
03
Compare ongoing use
Use the local energy or water label and include filters, detergent, bags and other consumables.
04
Check parts and service
Look for local technicians, realistic warranty coverage and the availability and price of common replacement parts.
Budget 10 watts per square foot in an insulated room with an 8 foot ceiling, so 1,500 watts really covers about 150 square feet. Cut that to 75 or 100 square feet for single pane windows, a floor over an unheated crawl space or a garage. A claim of 1,000 square feet describes air the fan can stir, not heat the element can add.
Measure three feet out from every face of the heater, including the top and the front, and clear it rather than eyeball it. A couch arm 18 inches from a radiant grille climbs to scorching temperature over a few hours, and heat too close to something combustible is the leading cause of these fires.
Nearly every cord is 6 feet or shorter and has to reach a wall outlet with no help. Position the heater by where an outlet already is, not where the room looks tidy. Never run the cord under a rug, across a doorway or behind furniture that pinches it.
One 1,500 watt heater draws 12.5 amps, leaving about 2.5 amps on a 15 amp circuit. Work out what else shares that breaker, because a kettle, a microwave, a hair dryer or a second heater will trip it. On a 230 volt supply outside the US the same 13 amps carries 2,000 to 3,000 watts. That means the ceiling is higher and local plug rules differ.
Only a heater marked by its maker for bathroom use belongs in a bathroom. It must run from a GFCI protected outlet, a device that cuts power within milliseconds if current leaks to ground. Nothing goes where a person in a tub or shower can reach it.
For a garage, workshop or addition, a 240 volt hardwired heater does what no plug-in unit can, at 3,000 to 5,000 watts. That is licensed electrician work: a new circuit, a disconnect and a permit in most places, with requirements that vary by country and municipality.
Care
Caring for space heaters
Vacuum the intake and outlet grilles once a month through the season, cold and unplugged. Dust felted onto an element insulates it, drives the internal temperature up and eventually trips the thermal cutout permanently. This is how most working heaters actually die.
Test the tip-over switch on the first cold day each year: run the heater, tilt it about ten degrees, and it should cut out before it leaves your hand. A switch that does not respond makes the whole unit scrap, because on carpet that is the protection doing the most work.
Fifteen minutes into a run, put a hand on the plug and the wall plate. Warm is normal and hot is not, since a hot outlet means worn contacts or a loose connection that an electrician should replace before you plug a heater in there again.
On an oil filled radiator, brush between the fins before each season and never drill, open or try to top up the reservoir. The oil is sealed for life and acts as a heat store rather than a fuel. A column that starts leaking cannot be repaired.
Keep connected models updated and recheck the schedule after every firmware update, because an update that restores factory settings can leave a heater running in an empty room. Never run one through a smart plug or mechanical timer unless that accessory is rated for 15 amps of resistive load.
Store it upright and dry at the end of winter with the cord coiled loosely instead of wound tight around the body, since repeated tight wrapping cracks the insulation right where the cord enters the housing. That is exactly where heater cords fail.
Questions
Common questions
How big a room will a 1,500 watt heater actually warm?
About 150 square feet, working from 10 watts per square foot in an insulated room with an 8 foot ceiling. Drop to 75 or 100 square feet for single pane windows, a room above an unheated space, or a garage. Listings that promise 1,000 square feet are describing air the fan can move, not heat the element can supply.
What does one cost to run?
At full output, 1.5 kilowatt hours every hour. Multiply by your rate: at 17 cents that is roughly 26 cents an hour, 2 dollars for an 8 hour evening and near 60 dollars over a month of daily use. A working thermostat cuts that by around a third once the room is warm, because the element stops instead of running.
Which type is cheapest to run?
None of them, and this is where marketing does the most damage. Every electric resistance heater turns essentially all the power it draws into heat, so 1,500 watts costs the same per hour whether the element is ceramic, quartz, oil warmed or bare wire. Your bill moves on the thermostat, the wattage setting and how long you leave it on.
Can I plug it into an extension cord or a power strip?
No. A 1,500 watt heater pulls 12.5 amps continuously, which overheats the light gauge wire inside household extension cords and the internal contacts of power strips and surge protectors. Melted cords are a leading ignition source in these fires. Plug it into a wall outlet directly, and if the outlet sits in the wrong place, move the heater or have an electrician add one.
Is it safe to leave one running while I sleep?
No, and no feature changes that. Tip-over switches and overheat cutouts back up a mistake you are present to catch, not your absence, and heating fire deaths cluster overnight because nobody is awake to smell smoke. Warm the room for an hour, switch the heater off before you get in, and let a slow cooling design carry the next 20 minutes.
Why does my heater keep tripping the breaker?
Because 12.5 amps leaves only 2.5 spare on a 15 amp circuit. Find what shares that breaker, since a microwave, kettle, hair dryer or second heater pushes it over. Switching to the 900 watt setting frees about 5 amps. If it trips with nothing else running, the breaker or the wiring needs an electrician rather than a different heater.
Ceramic or oil filled for a bedroom?
Oil filled, if you warm the room before bed and switch it off. It makes no noise, stirs no dust and hands heat back for 15 to 20 minutes after shutdown. Choose ceramic when you need the room usable in five minutes and will be awake in it, and accept roughly 45 decibels of fan noise on every cycle.
Why does it smell like burning the first time each winter?
Dust that settled on the element over summer is scorching off, and it should clear within 10 to 20 minutes with a window cracked. Vacuum the grilles first and it barely happens at all. A smell that lasts past half an hour, smells of hot plastic or arrives with a warm plug is different: unplug it and check the cord and outlet.
