Space Heater Cost Calculator

How to use this calculator

1. Look up your heater’s wattage on its label or in the manual (for example, 750 W on low and 1500 W on high) and enter the appropriate value.
2. Estimate how many hours per day you actually run the heater on average and enter that number.
3. Enter your electricity rate per kilowatt-hour from your latest utility bill or your provider’s website.
4. Review the calculator’s daily kWh, daily cost, and estimated monthly cost outputs.
5. Adjust wattage, hours, or rate to see how using a lower setting, cutting back runtime, or facing higher prices would change your bill.

Inputs explained

Heater wattage

The power rating of your heater in watts. Many plug-in space heaters draw about 1500 W on high and 750–1000 W on low. Use the wattage for the setting you use most.

Hours per day

The average number of hours per day the heater is actively running. If it runs intermittently, you can approximate its average by thinking in terms of total daily runtime.

Electricity rate ($/kWh)

Your cost per kilowatt-hour of electricity. This is often listed on your bill as an energy charge. If you have a time-of-use plan with higher peak rates, you can use an average or run separate scenarios for different times of day.

When to use it

• Estimating how much a space heater will add to your electric bill when used as supplemental heating in a home office, bedroom, or garage.
• Comparing the cost of different heater wattage settings or different models before purchase.
• Deciding whether it is cheaper to heat a single room with a space heater or to raise your central thermostat for the entire house.
• Budgeting for increased electricity usage during cold snaps or winter months when space heaters are likely to run more often.
• Helping family members or roommates understand the cost of leaving a heater running all day versus using it more selectively.

Tips & cautions

• Most thermostat-controlled heaters do not run at full power continuously—they cycle on and off. To approximate that behavior, use fewer effective hours per day than the total time the heater is switched on.
• Use the actual $/kWh rate from your electric bill for the most accurate estimate. If your bill shows multiple charges, using the energy charge line is a good starting point.
• Try running the calculator with both low and high wattage settings to see how much you save by using a lower setting when possible.
• If you routinely use more than one heater, run the numbers for each and add the costs together to get a fuller picture of your winter electric usage.
• Consider pairing this with a whole-home heating cost estimate to see whether you can lower your thermostat and rely on targeted space heating for frequently used rooms.
• Assumes the heater draws its full rated wattage for the hours entered; real heaters with thermostats or eco modes may consume less due to cycling.
• Does not explicitly model time-of-use or tiered pricing; if your rates vary by time or usage tier, a single blended rate is only an approximation.
• Focuses on one heater at a time; other loads on your circuit or in your home are not included in the calculation.
• Does not account for heating system interactions (for example, reduced furnace runtime when you use a space heater strategically).

Worked examples

Deep dive

FAQs

Why is my actual bill different from the estimate?

Real-world usage depends on thermostat cycling, room insulation, outside temperature, and your utility’s detailed rate structure (including fees and taxes). Treat these results as a planning estimate, not an exact prediction.

How can I find my exact electricity rate?

Check your electric bill for a per-kWh energy rate or divide the energy portion of your bill by the kWh used in the period. Your utility’s website may also list standard residential rates for your area.

Can I use this calculator for other appliances?

Yes. The same formula applies to any electric device with a roughly constant wattage: Daily kWh = (Watts × Hours per day) ÷ 1000, then multiply by $/kWh to get daily cost.

Does this consider tiered or time-of-use pricing?

Not directly. If your rates change based on usage level or time of day, you can approximate them with a blended rate or run separate scenarios for off-peak and peak hours.

Is using a space heater cheaper than central heating?

It can be, especially if you are only heating one small area and can lower the thermostat for the rest of the home. However, if you use multiple heaters heavily, costs can add up quickly. Use this tool alongside your knowledge of central system usage to compare.

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