A typical 1,500-watt space heater costs about $0.16-$0.32 per hour to run, while a gas furnace’s fuel cost is often about $0.05-$0.10 per hour for each 10,000 BTU of heat output at common U.S. gas prices. The actual space heater vs. gas heat cost depends mainly on electricity and natural gas rates, heater or furnace efficiency, and how much of the home needs heating.
| Item | Low | Average | High | Notes |
|---|---|---|---|---|
| 1,500-watt space heater | $0.16/hour | $0.24/hour | $0.32/hour | Based on electricity at $0.11-$0.21 per kWh |
| Gas furnace fuel per 10,000 BTU delivered | $0.04 | $0.06 | $0.10 | Varies by gas price and furnace efficiency |
| Space heater for 8 hours daily, 30 days | $38 | $58 | $77 | At 1,500 watts and the electricity rates above |
| Gas furnace for 8 hours daily, 30 days | $10 | $17 | $29 | Illustrative 60,000-BTU input furnace at $1-$2 per therm |
Assumptions: 1,500-watt electric heater, 60,000-BTU-per-hour gas furnace input, and stated residential utility-rate ranges; fixed monthly utility fees are excluded.
Typical hourly and monthly costs for room heat
A resistance space heater uses electricity at its rated wattage while its heating element is on. At 1,500 watts, it consumes 1.5 kWh per hour. Multiply that use by the household’s electricity rate: at $0.16 per kWh, the heater costs about $0.24 per operating hour, or $58 for eight hours a day over 30 days.
Gas heat is often cheaper per unit of delivered heat, but the furnace serves a larger area and cycles to maintain the thermostat setting. As an example, a furnace using 60,000 BTU of gas per hour consumes 0.6 therm per hour. At $1.50 per therm, its fuel costs $0.90 per hour while firing, before accounting for its useful heat output and duty cycle.
For one occupied room, a space heater can cost less overall by avoiding heat in empty rooms; for equal heat output, a gas furnace usually has the lower fuel cost. Actual monthly bills depend on run time, insulation, outdoor temperature, and whether the furnace would have run anyway.
Electricity, gas, and furnace efficiency in the quote
There is usually no installation quote for a portable space heater, but its operating expense is controlled by electricity rates and watts. A central gas system’s cost includes fuel, furnace efficiency, blower electricity, and maintenance. The table compares useful heat cost rather than the total household bill.
| Cost component | Space heater | Gas furnace | What changes the amount |
|---|---|---|---|
| Energy input | $0.11-$0.21 per kWh | $1.00-$2.00 per therm | Utility, plan, and location |
| Useful heat per input | About 3,412 BTU per kWh | About 80%-98% of fuel heat | Furnace age and efficiency rating |
| Delivered heat cost | About $0.032-$0.062 per 1,000 BTU | About $0.035-$0.085 per 1,000 BTU | Energy rate and equipment performance |
| Maintenance and equipment | $25-$100 purchase price; usually no service | $100-$300 annual tune-up; repairs extra | Equipment condition and service needs |
To estimate heater expense, use . A 1.5-kW heater running 6 hours daily at $0.18 per kWh costs 1.5 × 6 × $0.18, or $1.62 per day. Gas cost can be estimated as therms used multiplied by the gas rate; one therm contains about 100,000 BTU.
Compare the cost of delivered heat, not just the hourly bill: a furnace’s higher hourly total reflects substantially more heat capacity. Fixed customer charges and taxes can make the actual bill higher than these marginal-use estimates.
How electricity rates and gas prices change the break-even point
With resistance heat, each kWh becomes roughly 3,412 BTU of heat. At $0.16 per kWh, that heat costs about $0.047 per 1,000 BTU. A gas furnace operating at 90% efficiency costs about $0.057 per 1,000 BTU when gas is $1.50 per therm. Under those assumptions, electric resistance heat is slightly cheaper per delivered BTU, though rates can reverse the result.
At $0.21 per kWh, resistance heat costs about $0.062 per 1,000 BTU. Gas at $1.00 per therm and 95% efficiency is about $0.035 per 1,000 BTU, making furnace heat considerably less expensive per unit. Conversely, expensive gas or inexpensive electricity can narrow the gap or favor the space heater.
The approximate crossover electricity rate can be estimated by comparing the delivered-heat rates. For a 90%-efficient furnace using $1.50-per-therm gas, a resistance heater breaks even near $0.19 per kWh. This is an illustrative threshold, not a universal utility price; the delivered gas rate, furnace efficiency, and electricity bill’s variable charges matter.
Utility rates can change the answer more than the appliance’s purchase price. Use the marginal per-kWh and per-therm rates on current bills, rather than relying on national averages or a quoted introductory rate.
Room size, heater watts, and furnace BTU output
A standard 1,500-watt portable heater produces about 5,100 BTU per hour, enough for supplemental warmth in a modest, reasonably insulated room. Larger or draftier spaces may need longer run time or more heat than a single unit can provide. Plugging multiple high-wattage heaters into one circuit can overload it; the heater’s instructions and the circuit rating should govern use.
A residential gas furnace might have an input rating from roughly 40,000 to 100,000 BTU per hour. A 60,000-BTU-input furnace at 90% efficiency delivers about 54,000 BTU per hour while firing—more than ten times the heat output of a 1,500-watt heater. It also heats connected rooms, so comparing one heater’s hourly cost directly with a furnace’s hourly cost can mislead.
Insulation, ceiling height, window area, and air leakage determine how quickly heat escapes. A heater in a 120-square-foot insulated bedroom may cycle off regularly, while the same unit in a 250-square-foot room with drafty windows may run nearly continuously and still feel inadequate. Furnace sizing and zoning also affect how much heating reaches a particular room.
Match the comparison to the same area and comfort level, not simply to one hour of appliance operation. A smaller heat load can make localized electric heat useful even when gas is cheaper per BTU.
Three household examples with different run times
These examples use $0.16 per kWh for electricity and $1.50 per therm for gas. The gas estimate assumes 90% furnace efficiency and a 60,000-BTU-per-hour input furnace; it counts fuel only while the burner runs. Actual furnaces cycle, so equivalent comfort can require different run times.
| Scenario | Space heater use | Gas heat comparison | Estimated cost |
|---|---|---|---|
| Bedroom, 1,500 watts, 4 hours | 6 kWh per day | Localized room heat; furnace burner use varies | $0.96 daily, about $29 monthly |
| Home office, 1,500 watts, 8 hours | 12 kWh per day | About 10,200 BTU/hour heater output | $1.92 daily, about $58 monthly |
| Whole-home furnace, 60,000 BTU input, 4 burner-hours | Not equivalent to one portable heater | 2.4 therms per day at $1.50 per therm | $3.60 daily, about $108 monthly |
The whole-home example delivers about 216,000 BTU per day at 90% efficiency. It is not a direct cost comparison with the office heater, which provides only about 40,900 BTU over eight hours. For a fair comparison, a home’s heat demand and the area being heated must be similar.
Long run times make a portable heater’s daily expense add up quickly, even when it is inexpensive to buy. A thermostat-controlled unit may cycle off, so actual electricity use can be lower than the full-wattage estimate.
Regional utility rates shift the monthly comparison
Electricity and natural gas prices vary by state, utility, and rate plan. Areas with electricity around $0.11-$0.14 per kWh can make resistance heating relatively economical, particularly when gas is costly or unavailable. At $0.20-$0.30 per kWh, operating a 1,500-watt heater costs about $0.30-$0.45 per hour, raising the cost of extended use.
Gas rates near $1.00 per therm can make a high-efficiency furnace attractive for whole-home heat. Rates around $2.00 per therm double the fuel expense compared with $1.00 gas, before delivery charges and other bill items. A household’s quoted gas rate may include separate supply and delivery charges, so the variable total per therm is the relevant figure.
Seasonal bills also reflect climate. A cold northern winter can require many more heating hours than a mild winter in the South, while humid or cold conditions can affect comfort and thermostat settings. Local utility bills provide the best basis for estimating a particular month; national price averages cannot capture a specific home’s usage.
Recalculate with local rates before deciding which system to run for several hours each day. A small difference in per-unit price becomes significant when multiplied by winter usage.
Purchase, repairs, and safety beyond the energy bill
A basic portable space heater commonly costs $25-$100, while models with a fan, thermostat, tip-over shutoff, or extra controls often cost $40-$150. These are purchase prices, not guarantees of lower operating cost. A damaged cord, loose outlet, or heater without appropriate safety features can create risks, and extension cords should not be used unless the manufacturer explicitly permits them.
A gas furnace tune-up commonly costs $100-$300, while repairs can range from roughly $150 for a simple component to $1,000 or more for major parts or complex work. Replacement is a separate project, often costing several thousand dollars depending on capacity, venting, labor, and duct changes. Those costs should not be assigned to a space heater comparison unless the furnace needs the work regardless.
Portable heaters should be kept away from bedding, curtains, and furniture, placed on a stable surface, and switched off when unattended or sleeping unless the manufacturer’s instructions say otherwise. Gas furnaces require functioning venting and carbon monoxide alarms. Safety rules and building requirements vary, and a heater should never be used to heat an area in a way its listing or instructions prohibit.
Include equipment condition and safe operation in the comparison, not only the monthly energy charge. A low purchase price does not compensate for unsafe use or an unserviced furnace.
Which heating choice costs less for one room or the whole home?
For a room used only part of the day, a space heater can lower the total bill if the central thermostat is turned down and the rest of the home does not need heat. If the furnace would run anyway to keep other rooms comfortable, adding a portable heater may increase electricity use without replacing much gas consumption.
For a whole home, a gas furnace usually makes more sense than using multiple resistance heaters when gas is reasonably priced. Several 1,500-watt heaters can draw substantial electrical load, and their combined energy cost can exceed furnace fuel costs. A heat pump, if already installed, is another comparison: it can deliver more than one unit of heat per unit of electricity and may cost less to operate than resistance heat, depending on outdoor temperature and rates.
To reduce the bill without buying new equipment, heat only occupied rooms when practical, close doors where appropriate, seal obvious drafts, and avoid setting the central thermostat higher than needed. Do not shut vents or alter furnace airflow without following system guidance, because improper airflow can affect performance.
Use a space heater as targeted supplemental heat, not automatically as a substitute for a gas furnace across the entire home. The least expensive choice depends on whether it truly avoids central heating and how many hours the room needs warmth.