Electricity bill calculator
Estimate the energy (kWh) and cost of running an appliance from its wattage, daily hours and days, with a three-tier tariff, multiple units and a configurable CO₂ factor.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Appliance and tariff
Energy = watts × hours per day × days × units ÷ 1000. Tier limits, rates and the CO₂ factor are all editable — the defaults are references only, so use your local tariff and published emission factor.
Estimate
240.00 kWh
8.00 kWh
240.00 kWh
2920.00 kWh
120.00
4.00
0.5000 per kWh
Tier 1
139.44 kg CO₂
Tier 1: 240.00 kWh × 0.50 = 120.00
What this tool does
- Find out what an appliance really costs: enter its wattage and usage hours to see the energy and cost per month and per year.
- Compare an air conditioner running 8 hours with a heater running 4 hours — change the wattage and hours and the results are directly comparable.
- See the marginal cost of extra usage under a tiered tariff: once you cross into the second tier, that rate is what one more kWh actually costs.
- Budget the electricity for a flat or office and estimate the associated CO₂ (swap in your own emission factor).
Example
Input
1000 W appliance, 8 hours a day, 30 days, 1 unit; tiers: 0.5 up to 240 kWh, 0.55 up to 400 kWh, 0.8 beyond; CO₂ factor 0.581
Output
Energy 240.00 kWh, energy per day 8.00 kWh, cost 120.00, average price 0.5000, tier 1, estimated CO₂ 139.44 kg CO₂
Tiers and the CO₂ factor are configurable references: 0.581 kg CO₂/kWh is only the order of magnitude of a typical grid average, so replace it with your local published figure.
Frequently asked questions
Why is the bill not simply total kWh × one price?
Tiered tariffs accumulate band by band: the first 240 kWh at the first rate, 240–400 kWh at the second, and only the excess above 400 kWh at the third. So 500 kWh is 240×0.5 + 160×0.55 + 100×0.8 = 288, not 500 × 0.8.
Where does the 0.581 kg CO₂/kWh factor come from?
It is a reference for the order of magnitude of a grid average, not official data, which is why the field is editable. For an accurate figure use your grid’s published annual average factor, or set it to 0 to look at cost only.
Can the hours per day exceed 24?
No — one appliance cannot run more than 24 hours a day. If several identical units run at once, raise the unit count instead of inflating the hours, so the tier calculation stays correct.
Why does the estimate differ from my actual bill?
This only covers the appliance you entered. A real bill also includes other appliances, standby draw, shared charges and various surcharges. It is accurate for comparing appliances and sizing costs, but it is not a substitute for the invoice.
Is my data uploaded anywhere?
No. Everything is computed locally in the browser, the page makes no network requests, and a refresh clears your input.
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