DIY Home Calculators

Electricity bill calculator

This electricity bill calculator estimates your monthly and yearly cost from three numbers: how many kWh you use, the unit rate and the daily standing charge. It also reveals your effective price per kWh, which is almost always higher than the unit rate on your tariff sheet.

kWh

Your bill shows kWh for the period. Divide by months covered.

€ per kWh
€ per day

Fixed daily charge. It may be shown per month or per year on your bill, so convert it.

%

Leave at 0 if your rates already include VAT, as consumer prices usually do.

How an electricity bill is built

Most household bills combine a usage charge and a fixed charge.

Usage charge = kWh used × unit rate
Standing charge = daily standing charge × days in the period
Bill = (usage charge + standing charge) × (1 + extra VAT)

Consumer prices in most countries already include VAT, so the VAT field defaults to zero. Only use it if the rates you type in are quoted before VAT. The calculator converts a daily standing charge to a monthly figure by multiplying by 365 and dividing by 12.

Worked example

A household uses 250 kWh a month. The unit rate is 0.28 per kWh and the standing charge is 0.45 per day.

  • Usage: 250 × 0.28 is 70.00.
  • Standing charge: 0.45 × 365 ÷ 12 is 13.69.
  • Monthly bill: 83.69, or 1,004 a year.
  • Effective price: 83.69 ÷ 250 is 0.335 per kWh.
  • The standing charge makes up 16.4 percent of the bill.

Why low-use homes pay more per kWh

The standing charge does not depend on how much you use. Spread it over fewer kWh and the effective price climbs. Halve the household's use to 100 kWh a month and the bill drops to only 41.69, but the effective price rises to 0.417 per kWh and the standing charge reaches 32.8 percent of the bill. This is why tariffs with a low unit rate and a high standing charge suit heavy users, and tariffs with a higher unit rate and a low standing charge suit people who use little.

When you compare tariffs, do not compare unit rates alone. Enter the unit rate and standing charge of each offer into the calculator at your own annual use and compare the totals.

Finding your numbers

Your latest bill states the period it covers, the kWh used, the unit rate and the standing charge. Divide the kWh by the number of months to get a monthly figure. If your bill shows the standing charge per month or per year, convert it to a daily figure: a monthly charge multiplied by 12 and divided by 365, or a yearly charge divided by 365.

Smart meters and supplier apps often show daily or half-hourly use, which helps if your consumption changes with the seasons. For a yearly estimate, use the total of the last twelve months, not a single winter or summer month.

What the estimate leaves out

Some suppliers add network fees, levies or taxes as separate lines, so check whether your unit rate already includes them. Time-of-use tariffs have different prices at different hours, and a single unit rate is an average of those. A fixed-term deal may also carry an exit fee that is not part of the bill. Where a bill includes a fixed amount for a service plan or smart meter rental, add it to the standing charge.

Frequently asked questions

How many kWh does an average home use?

It varies widely with country, home size, heating type and household size. Compare your own bills over time rather than a national average, since your home is the one you pay for.

Is the standing charge negotiable?

Not within a tariff, but different tariffs set it differently. Switching to one that suits your use pattern is the practical lever.

Why is my real bill higher than the estimate?

Check for network charges, levies and rental fees on the bill. Also check that the kWh figure is a full-year average and not a mild month.

Should I use gross or net prices?

Use the gross price you pay as a consumer, including VAT, unless the rate is quoted before VAT, in which case add VAT in the VAT field.

Reviewed 9 November 2026 by Mudassar Hussnain, DIY Home Calculators. Formulas are documented on How we calculate. Corrections are logged on the editorial policy page.