Electricity Bill Estimator

How electricity bills actually work

Most residential bills combine two elements: a usage charge based on the kilowatt-hours consumed, and a fixed charge, sometimes called a standing or service charge, that covers the meter, the connection and the network whether any power is used or not. Usage is the larger component for most households, but the fixed charge matters because it does not respond to cutting consumption. With the defaults on this page, the fixed fee is 12 of a 138 bill, or 8.7%, so cutting usage by 30% (900 kWh down to 630) cuts the bill by 27.4%, to 100.20, not by 30%. Where the fixed charge is a bigger slice, the gap widens.

Typical household usage and rates

Both inputs vary enormously by country, and by region within a country, so the figures on the last bill are the ones that belong in the fields. For scale: the US Energy Information Administration puts the average annual consumption of a residential customer at 10,791 kWh in 2022, about 899 kWh a month. The same agency's 2025 average residential price is 17.30 cents per kWh, with retail prices across all customer types ranging from 8.20 cents in North Dakota to 35.72 cents in Hawaii. In the European Union, Eurostat's household average for the second half of 2025 was €0.2896 per kWh including taxes and levies, with Irish households paying 40% above that average and households in Hungary, Malta and Bulgaria less than half of it. A rate at one end of those ranges and a rate at the other produce bills more than four times apart on the same usage.

Common things people overlook

Three features of real tariffs move bills away from this simple model. Tiered rates charge more per kWh above a threshold, so heavy users pay a higher average rate than the headline; the closest fit here is the bill's total energy charge divided by its kWh, which is the weighted-average rate. Demand charges add a fee based on the highest short-period draw in the month, which no usage figure captures. Time-of-use pricing charges different rates by hour or season, so when the laundry, the dishwasher or a car charger runs changes the bill without changing the kWh. The calculator uses one flat rate, which is exactly right for a flat tariff and an approximation for the rest.

A worked example

With the defaults, 900 kWh at 0.14 per kWh is a usage charge of 126. Adding the 12 fixed fee gives 138.00 a month, which is 1,656 a year and 4.60 a day on a 30-day month. Of the 138, 91.3% is usage and 8.7% is the fixed fee.

What moves the number most

Usage and rate multiply together, so a 10% rise in either lifts the bill by 9.1%; the fixed fee is the only input that moves the bill one-for-one. Adding 100 kWh takes the default bill from 138 to 152. Raising the rate from 0.14 to 0.20 takes it to 192. That is the largest swing on the page. Doubling the fixed fee to 24 adds only 12, to 150. Halving usage to 450 kWh brings the bill to 75, not 69, because the fee stays.

The formula behind this

Monthly bill equals usage in kWh multiplied by the rate per kWh, plus the fixed monthly fee. The annual figure is twelve times the monthly bill and the daily average is the monthly bill divided by 30. Nothing else is applied: no tiers, no demand charges, no time-of-use bands, and no taxes or surcharges beyond whatever is already inside the rate entered.

Using the result when comparing tariffs

An annual figure built from the household's own kWh is what makes tariff comparisons like-for-like, because suppliers quote rates and standing charges separately and a low rate can hide a high fixed fee. Running two tariffs through the calculator at the same usage puts them on the same footing: tariff A at 0.16 per kWh with a 5 fee and tariff B at 0.14 with a 12 fee cost 149 and 138 a month at 900 kWh, but at 300 kWh the order flips to 53 against 54. The break-even sits where the fee difference equals the rate difference multiplied by the usage, which here is 350 kWh a month.