Calculator Inputs
Enter your heater details, billing assumptions, and optional standby or seasonal factors. Results appear above this form after calculation.
Example Data Table
These sample scenarios help you understand common heater sizes, usage patterns, and estimated monthly running cost assumptions.
| Heater Type | Wattage | Qty | Hours/Day | Tariff/kWh | Estimated Daily kWh | Estimated Monthly Cost |
|---|---|---|---|---|---|---|
| Ceramic Space Heater | 1500 W | 1 | 6 h | $0.18 | 6.51 | $37.16 |
| Oil-Filled Radiator | 1200 W | 2 | 5 h | $0.16 | 8.88 | $47.94 |
| Panel Heater | 1000 W | 3 | 4 h | $0.20 | 9.36 | $60.31 |
| Fan Heater | 2000 W | 1 | 3 h | $0.22 | 4.44 | $31.37 |
Formula Used
(Heater Wattage × Quantity) ÷ 1000
Hours Used Per Day × (Duty Cycle ÷ 100)
Connected Load × Effective Heating Hours
(Standby Watts × Quantity) ÷ 1000
Standby Load × Standby Hours Per Day
(Daily Active Energy + Daily Standby Energy) × Seasonal Multiplier
(Energy × Tariff) + Fixed Fee Allocation
Cost Before Tax × (1 + Tax Rate)
This model uses duty cycle to represent thermostat cycling. For many room heaters, it gives a more realistic estimate than assuming full power all day.
How to Use This Calculator
- Enter the heater wattage for one unit.
- Add the number of heaters running in the same period.
- Enter average daily use hours and monthly usage days.
- Provide your electricity tariff per kilowatt-hour.
- Adjust the duty cycle to reflect thermostat behavior.
- Include standby watts and standby hours if relevant.
- Apply seasonal multiplier, tax rate, and fixed charges.
- Click Calculate Cost to see results above the form.
- Use the CSV and PDF buttons to export your results.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates electric heater energy use and running cost across daily, weekly, monthly, and yearly periods. It also shows active load, standby load, tax impact, fixed fees, and emissions.
2. Why is duty cycle important?
Most heaters do not draw full rated power every minute. Thermostats cycle power on and off. Duty cycle reflects that behavior and makes cost estimates more realistic.
3. Should I enter heater efficiency?
For most electric resistance heaters, electrical input almost equals heat output at the room level. Duty cycle usually matters more than efficiency when estimating electricity cost.
4. What is standby power?
Standby power is the electricity a heater uses while plugged in but not actively heating. Digital displays, Wi-Fi modules, or control boards can still consume small amounts.
5. Can I use this for multiple heaters?
Yes. Enter the number of heaters in the quantity field. The calculator multiplies active and standby load by that count before estimating energy use and total cost.
6. What does the seasonal multiplier do?
It scales energy use to reflect colder or warmer periods. A value above 1 increases estimated usage, while a value below 1 reduces it.
7. Are taxes and fixed fees necessary?
They are optional, but they help match real bills. Some utilities apply taxes, surcharges, or fixed monthly service costs that affect the final amount paid.
8. Is this calculator suitable for commercial spaces?
Yes, for quick estimates. For precise commercial analysis, also consider demand charges, time-of-use tariffs, zoning controls, occupancy schedules, and building heat loss.