Space Heater Cost Calculator — Free Online Calculator
Calculate how much a space heater costs to run per hour, day, and month based on wattage and electricity rate.
How to Use This Calculator
Select heater wattage, enter daily usage hours and electricity rate.
The Formula Explained
Cost per hour = Watts / 1000 × Rate. A 1500W heater at $0.15/kWh costs $0.225 per hour.
Space Heater Economics: Hot Spot Math
Space heaters are often marketed as money-saving devices that let you avoid central heating costs. The truth is more nuanced: space heaters only save money in specific circumstances, and used incorrectly they can actually increase your electric bill dramatically. The economics hinge on a simple tradeoff: electric resistance heating costs 3-5 times more per BTU than natural gas, but heating only the room you use can avoid wasting heat on unoccupied areas.
The calculation is straightforward. A 1,500W space heater consumes 1.5 kWh per hour of full-power operation. At 16 cents per kWh, that is 24 cents per hour, or 1.92 USD for 8 hours, or 58 USD per month of daily 8-hour use. For whole-house heating with gas, the same 12 kWh of heat costs about 12 cents per hour (gas at 1.10 USD per therm delivering 100,000 BTU, 4x more heat per dollar than electric). A space heater running 8 hours per day can add 30-60 USD per month to your electric bill during winter.
Worked Example: Home Office Heating
A 200 sq ft home office where someone works 8 hours per day, 5 days per week. Option A: turn up the whole-house thermostat from 65°F to 72°F for those 8 hours. Option B: keep the house at 65°F and run a 1,500W space heater in the office.
Option A (gas central heat): Raising 2,000 sq ft home by 7 degrees for 8 hours requires roughly 30,000 BTU/hr additional heating for that duration. Total: 240,000 BTU × 40 hours per week = 9.6 million BTU per month. At 80% furnace efficiency: 12 million BTU gas input. At 1.10 USD per therm (100,000 BTU): 132 USD per month extra heating cost.
Option B (electric space heater): 1,500W × 8 hours × 22 workdays = 264 kWh per month. At 16 cents: 42.24 USD per month. Winner: space heater, by about 90 USD per month.
Flip the scenario: someone working from home 12 hours per day in multiple rooms, or a household with multiple occupants spread across rooms. Multiple space heaters running across different rooms quickly exceed central heating cost, because the whole-house system gains efficiency through scale.
Worked Example: Heat Pump Comparison
A modern cold-climate heat pump (COP 3.0 at 30°F outdoor temperature) delivers 3 units of heat for each unit of electrical input. For 1,500W of electrical input, the heat pump delivers 4,500W of heat equivalent — equivalent to three 1,500W space heaters running at once.
Heating cost comparison per BTU delivered: Space heater: 1 BTU per watt-hour of input, at 16 cents per kWh = 0.0469 cents per 1,000 BTU. Heat pump at COP 3.0: 3 BTU per watt-hour, same rate = 0.0156 cents per 1,000 BTU. Natural gas at 80% efficient furnace, 1.10 USD/therm: 0.0138 cents per 1,000 BTU.
So a modern heat pump is nearly as cheap as gas heating and 3x cheaper than space heaters. This is why heat pumps are rapidly replacing both gas furnaces (in warming regions) and electric resistance heating (in cold regions with cheap electricity). Space heaters remain useful for short-duration spot heating but are terrible as primary heat sources.
Space Heater Mistakes
1. Leaving them running in unoccupied rooms. The point of a space heater is to heat only where you are. Auto-shutoff timers and occupancy sensors prevent waste.
2. Running them to supplement central heat. If you are running both, you are paying for heat twice. Either lower central heat and rely on space heaters, or run central heat and skip space heaters.
3. Using them on overloaded circuits. A 1,500W heater is 12.5A on a 15A circuit. Add any other device and you exceed the circuit. Use dedicated outlets for space heaters; do not share with computers, lights, or other electronics.
4. Underestimating fire risk. Space heaters are a leading cause of residential fires. Keep 3 feet clear on all sides, never leave them running when sleeping or leaving, and never on extension cords.
5. Choosing based on "efficiency" claims. All electric resistance heaters are 100% efficient. Marketing claims of "90% heating efficiency improvement" are misleading. The real comparison is with heat pumps or gas heat, not between space heater models.
Operating Cost Quick Reference
At 16 cents per kWh:
500W heater, 8 hours/day: 19 USD/month.
750W heater, 8 hours/day: 29 USD/month.
1,000W heater, 8 hours/day: 38 USD/month.
1,500W heater, 8 hours/day: 58 USD/month.
1,500W heater, 24 hours/day: 173 USD/month.
1,500W heater, season (5 months, 8 hr/day): 288 USD.
Comparisons:
Whole-home gas heat (2,000 sq ft, mild climate): 80-150 USD/month winter.
Whole-home gas heat (3,000 sq ft, cold climate): 150-300 USD/month winter.
Whole-home heat pump (modern, efficient): 40-80 USD/month mild climate.
Electric baseboard heat (whole home, 2,000 sq ft): 300-600 USD/month winter.
Safety Standards
Space heaters sold in the US must carry UL or ETL listing (UL 1278 for fan-forced heaters, UL 2021 for other portable electric heaters). Modern heaters include tip-over shutoff, overheat protection, cool-touch housings, and GFCI plugs for bathroom units. Never use heaters without these features.
NFPA data: portable heaters cause about 1,700 residential fires per year in the US, with 80% attributed to combustibles too close to the heater and 20% to electrical faults. Keep 3-foot clearance from bedding, furniture, curtains, and paper. Never use extension cords — they overheat and start cord fires.
Space heater cost: resistance heat math and when it makes sense
A space heater is the simplest electrical load: nearly 100 percent of input power becomes heat. The cost is just watts times hours times rate. What makes space heaters expensive is not the per-hour cost, it is that they run a lot if used as primary heat. They are best as supplemental heat in one occupied room while the main system runs lower, or for short-duration spot heating.
The formula and what it does
Same as electricity cost for any resistive load. A typical "1500 W" space heater on high pulls 1,500 W and produces 1,500 W of heat (about 5,118 BTU/hr). On low (often 750 W), produces half that. Modern heaters with thermostats cycle on/off based on room temp.
Worked example
Scenario: 1500 W space heater on high for 8 hours/day, 90 cold-weather days, in three different states.
Daily kWh: 1.5 x 8 = 12 kWh. Annual season: 12 x 90 = 1,080 kWh. Cost at Texas 14.3 cents: 54.44. At US avg 16.4 cents: 77.12. At Mass 29.4 cents: $317.52. Now compare a mini-split heat pump heating the same room: COP 3.0 in moderate winter conditions, so same 5,118 BTU/hr requires only 500 W of input. Same hours: 360 kWh per season. Texas cost: $51.48 (saves 03). California cost: 10.88 (saves $206). Heat pump wins everywhere, especially in expensive-power states.
US residential electricity rates (April 2026, top + bottom states)
| State | Avg rate (c/kWh) | Monthly bill, 900 kWh |
|---|---|---|
| Hawaii | 41.2 | $371 |
| California | 30.8 | $277 |
| Massachusetts | 29.4 | $265 |
| Connecticut | 28.6 | $257 |
| New York | 23.1 | $208 |
| US average | 16.4 | 48 |
| Texas | 14.3 | 29 |
| Florida | 13.7 | 23 |
| Washington | 11.2 | 01 |
| Idaho | 10.6 | $95 |
| North Dakota | 10.4 | $94 |
Source: US Energy Information Administration (EIA) Electric Power Monthly, April 2026 release. Rates are residential class average including delivery and supply charges.
Common mistakes to avoid
undefinedFrequently asked questions
Are oil-filled and ceramic heaters more efficient than coil?
No. All electric-resistance heaters are 100 percent efficient at converting electricity to heat. Differences are in heat distribution pattern, surface temperature (safety), and noise. Per BTU output, all cost the same to run.
What about "energy-saving" infrared heaters?
Marketing. Infrared heaters are still 100 percent efficient electric resistance. The "energy saving" claim comes from heating people directly via radiation rather than warming room air, which is valid for targeted use in a large cold space but not magic efficiency.
Is a space heater cheaper than running central heat?
Sometimes. If you can cool down the whole house and use a space heater in one occupied room, yes. If you run the space heater alongside central heat, no, you just added load. The economics depend on whether you actually turn down the main system.
Is electric heating ever cheaper than gas?
For resistance heat: very rarely. Gas at .20/therm provides 100,000 BTU for .20. Electric resistance at 16 cents/kWh provides 100,000 BTU for $4.69. For heat pumps with COP 3+: yes, in moderate climates, heat pump beats gas at most rates.
How much heat does 1500 W produce?
1500 W = 5,118 BTU/hr. Enough to heat a well-insulated 150-200 sq-ft room. For larger spaces or poorly insulated rooms, multiple heaters or a different solution.
Can my house circuit handle a 1500 W heater?
Yes on a dedicated 15 A or 20 A circuit. The heater pulls 12.5 A on 120 V. Avoid sharing the circuit with other heavy loads (extension cords are particularly risky here). Never daisy-chain space heaters on power strips.