Space Heater Running Cost Calculator
Estimate what a space heater costs per hour, day, month and season from its wattage, hours of use per day and your electricity price per kWh.
Space Heater Running Cost Calculator: with the default inputs, cost per month is $61.20.
Nameplate wattage. Most plug-in heaters are 750 W (low) or 1500 W (high).
Use the all-in rate from your bill (supply + delivery), not just the energy charge.
Share of the switched-on time the element actually draws power. A thermostat cycling on and off might be 50-70%.
Used only for the seasonal total.
- Electricity used per hour
- 1.5Effective kilowatt-hours drawn for each hour the heater is switched on.
- Cost per hour on
- $0.255
- Electricity used per day
- 12
- Cost per day
- $2.04
- Electricity used per month
- 360
- Cost for the heating season
- $244.80
- Heat output while running
- 5,118BTU per hour at full power. Electric resistance heat is ~100% efficient at the heater.
Assumptions
- Electric resistance heating is treated as 100% efficient at the point of use, so watts drawn equal heat delivered.
- A single flat price per kWh is applied; tiered, seasonal and time-of-use tariffs are not modelled.
- Power draw is assumed equal to the nameplate rating whenever the element is on.
- Duty cycle scales energy use linearly and defaults to 100% (continuous operation).
How this is worked out
The formula
kWh per hour = (watts / 1000) x (duty cycle % / 100) x number of heaters Cost per hour = kWh per hour x price per kWh kWh per month = kWh per hour x hours per day x days per month Cost per month = kWh per month x price per kWh Heat output (BTU/h) = watts x 3.412
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Heater power rating
- Nameplate wattage. Most plug-in heaters are 750 W (low) or 1500 W (high).from 50 to 7000 · defaults to 1500
- Hours switched on per day
- A number.from 0 to 24 · defaults to 8
- Days used per month
- A number.from 1 to 31 · defaults to 30
- Electricity price
- Use the all-in rate from your bill (supply + delivery), not just the energy charge.in dollars · from 0 to 2 · defaults to 0.17
- Thermostat duty cycle
- Share of the switched-on time the element actually draws power. A thermostat cycling on and off might be 50-70%.a percentage · from 1 to 100 · defaults to 100
- Number of heaters
- A number.from 1 to 20 · defaults to 1
- Months of heating season
- Used only for the seasonal total.from 1 to 12 · defaults to 4
What you get back
- Cost per monthmain answer
- Electricity used per hour
- Effective kilowatt-hours drawn for each hour the heater is switched on.
- Cost per hour on
- Electricity used per day
- Cost per day
- Electricity used per month
- Cost for the heating season
- Heat output while running
- BTU per hour at full power. Electric resistance heat is ~100% efficient at the heater.
What this assumes
- Electric resistance heating is treated as 100% efficient at the point of use, so watts drawn equal heat delivered.
- A single flat price per kWh is applied; tiered, seasonal and time-of-use tariffs are not modelled.
- Power draw is assumed equal to the nameplate rating whenever the element is on.
- Duty cycle scales energy use linearly and defaults to 100% (continuous operation).
About this calculator
What this calculator does
Electric space heaters are simple to price out: they turn essentially every watt they draw into heat, so the cost depends only on power, run time and your electricity rate. This calculator converts a heater's nameplate wattage into kilowatt-hours and multiplies by the price you pay per kWh to give cost per hour, per day, per month and for a whole heating season.
How to use it
Enter the wattage printed on the heater or its label (1500 W is the ceiling for a standard 120 V outlet in North America; 2000-3000 W is common on 230 V circuits). Add the hours per day it is switched on and how many days per month you use it.
For the electricity price, use your all-in rate: divide the total bill by the kWh delivered, so that delivery charges, riders and taxes are included. That is usually noticeably higher than the headline energy rate.
The duty cycle matters most. A heater with a thermostat does not run continuously — once the room reaches temperature the element cycles off. If the heater is on for 8 hours but only heating half the time, set the duty cycle to 50% and the cost halves. Set it to 100% for a heater run flat out on manual high.
Where it is approximate
Actual draw can differ from the nameplate by a few percent, and voltage sag on a long circuit reduces both power and heat. Duty cycle is a guess unless you measure with a plug-in energy meter. Fan and electronics consume a watt or two extra, which is negligible. Tiered or time-of-use tariffs mean your marginal rate may be higher than your average rate.
Frequently asked questions
▸How much does a 1500 W heater cost per hour?
At full power it uses 1.5 kWh per hour. At $0.17 per kWh that is about $0.26 per hour, roughly $2.04 for an 8-hour day and about $61 over a 30-day month. With a thermostat cycling at 50% duty, halve those figures.
▸Should I use the low or high setting in the calculator?
Enter the wattage of the setting you actually use. Many heaters offer 750 W low and 1500 W high. Running on low costs half as much per hour, but it may need to run longer to reach the same temperature, so total energy can be similar.
▸What duty cycle should I choose?
If the heater has no thermostat, or you run it in a cold, poorly insulated room, use 90-100%. For a small, well-insulated room where the thermostat clicks off regularly, 40-70% is realistic. A plug-in energy monitor gives the exact figure.
▸Are 'energy-efficient' space heaters cheaper to run?
Not per unit of heat. All resistance heaters — ceramic, oil-filled, infrared, quartz — convert electricity to heat at essentially 100%. Savings come from better thermostats, timers, zoning and directing heat at people, not from higher efficiency. Only a heat pump beats resistance heating on cost per unit of heat.
▸Why is my bill higher than this estimate?
Common reasons are using the energy-only rate instead of the all-in rate, underestimating hours or duty cycle, extra usage pushing you into a higher tariff tier, or the heater being on during peak-price hours.
How this calculator was made
A visitor asked for: “Cost to run a space heater for a month from its wattage, hours used per day and the price per kilowatt-hour”. An AI model wrote the formulas as a declarative spec, our engine checked that every expression parses and evaluates, and the math above runs deterministically in your browser. It hasn’t been reviewed by a person yet — check the assumptions and the How it’s calculated panel before relying on it.