Electric Space Heater Running Cost Calculator
Estimate electric space-heater energy use and cost from wattage, heater quantity, thermostat duty cycle, runtime and electricity price.
Default project preview
$42.12 per month
Daily energy
7.8 kWh
Daily cost
$1.40
Monthly energy
234 kWh
Seasonal cost
$210.60
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Rated heater power
Enter this project assumption in W. The current imperial default is 1500 W.
Number of heaters
Enter this project assumption in heaters. The current imperial default is 1 heaters. Minimum: 1.
Hours available per day
Enter this project assumption in hr/day. The current imperial default is 8 hr/day.
Thermostat duty cycle
Enter this project assumption in %. The current imperial default is 65 %. Minimum: 1. Maximum: 100.
Heating days per month
Enter this project assumption in days. The current imperial default is 30 days. Minimum: 1. Maximum: 31.
Heating-season months
Enter this project assumption in months. The current imperial default is 5 months. Minimum: 1. Maximum: 12.
Electricity rate
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
Daily energy
5.2 active hours. Default preview: 7.8 kWh.
Daily cost
energy × entered rate. Default preview: $1.40.
Monthly energy
30 heating days. Default preview: 234 kWh.
Seasonal cost
5 months. Default preview: $210.60.
Connected heater load
1 heater. Default preview: 1.5 kW.
Full-power monthly cost
100% duty-cycle comparison. Default preview: $64.80.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Active hours = available hours × thermostat duty cycle. Energy = heater kW × heater count × active hours. Cost = kWh × electricity rate.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use the Electric Space Heater Running Cost Calculator to estimate a planning quantity from verified heater wattage, runtime and electricity tariff. It supports scope comparison, purchasing and operating-cost planning, but it does not select equipment, approve code compliance or replace project-specific design.
Calculation steps
- 1Measure or obtain each design input from the actual project and keep one consistent unit system.
- 2Enter heater wattage, runtime and electricity tariff using product data or approved design information rather than generic nominal values.
- 3Review the unrounded engineering or usage result before applying allowances, duty cycle, efficiency or tariff assumptions.
- 4Apply each adjustment once, then round only the final purchasing, equipment-count or scheduling output.
Worked numerical example
A 1.5 kW resistance heater used 5 hours consumes 7.5 kWh; at $0.22/kWh the session costs about $1.65.
Purchasing and rounding
Use the heater electrical input shown on its rating label and the utility energy rate. Do not add a waste factor: resistance heaters convert nearly all point-of-use electrical input to room heat, while thermostat cycling changes runtime.
Interpret the result
The calculation gives energy and cost for the entered hours. It does not predict how long the heater must run to hold temperature, which depends on building heat loss and thermostat behavior.
Page-specific assumptions
- Inputs describe the actual connected system or measured project scope.
- One operating condition, product rating and unit system are used per calculation.
- Allowances and efficiency losses are not already embedded in the entered values.
- Code, health, structural, electrical and hydraulic requirements are verified independently.
Common mistakes
- Using nominal equipment ratings instead of delivered performance at design conditions.
- Mixing instantaneous flow or power with daily or annual energy.
- Applying the same allowance more than once.
- Treating a quantity or cost estimate as equipment selection or professional approval.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Electric Space Heater Running Cost Calculator questions
What is thermostat duty cycle?+
It is the share of available time the heating element is actually energized. A heater that cycles on half the time has about a 50% duty cycle.
Do all electric resistance heaters cost the same to run?+
At the same wattage and runtime, their electricity cost is similar. Comfort and heat distribution can still differ.
Why show full-power cost?+
It provides an upper comparison when the heater runs continuously instead of cycling at the entered duty rate.