Electricity Cost Calculator

Power ratings on appliances and light bulbs are almost always printed in watts, but electricity is billed in kilowatt-hours — a kilowatt is 1,000 watts. Dividing the wattage by 1,000 converts it to kilowatts before multiplying by hours, which is what turns a nameplate rating into the same kWh unit your utility bill uses.

Rather than picking an arbitrary 28, 30, or 31-day month, this calculator uses the year's average: 365 days ÷ 12 ≈ 30.44 days per month. That keeps the numbers internally consistent — twelve monthly figures always add up to the yearly total exactly, instead of drifting depending on which months you'd otherwise have picked.

Only if you account for it in the hours field. Many electronics still pull a small amount of power while "off" but plugged in — phone chargers, game consoles, and TVs are common offenders. If you want that reflected, either add an extra row estimating the standby wattage over the remaining hours in the day, or use a plug-in power meter to measure the appliance's true average draw.

Yes — add a row for each appliance with its own wattage and usage time. Every row shows its own daily energy and cost right under its fields, so you can see at a glance which one costs more to run, while the totals at the bottom combine all of them into a single household figure.

Enter a blended average rate (total dollars billed ÷ total kWh used from a recent statement) for a reasonable estimate. This calculator assumes one constant rate per kWh, so it won't capture peak/off-peak swings or usage-tier jumps exactly — for a bill with strong time-of-use pricing, run the calculation once per rate tier and add the results.

Real appliances rarely draw a perfectly constant wattage — a refrigerator compressor cycles on and off, a space heater's thermostat clicks in and out, and a laptop draws more under load than idle. The nameplate or average wattage you enter is a simplification; for the most accurate estimate, measure actual draw over a day with a plug-in power meter instead of relying on the printed rating.

Nameplate wattage (printed on the appliance or its power supply) is a maximum rating, so it tends to overestimate real-world cost for anything that cycles or varies its draw, like heaters, fridges, and motors. A plug-in power meter reading the appliance's actual average watts gives a more realistic result — use the nameplate figure only as a worst-case upper bound.