Electricity bill calculator: estimate your monthly bill

How this electricity bill calculator works

An electricity bill has two parts: a variable part that scales with the kWh you use, and a fixed part you pay regardless. This calculator rebuilds both. You can start from the kWh shown on a past bill or from a list of the appliances you actually use. The list is more useful when you are budgeting for a new home, a new appliance or a tariff switch.

In appliance mode, each of the 19 rows uses the unit people naturally think in: cycles per week for washing machines and dishwashers, hours per day for TVs and hobs, boils per day for kettles, km per day for an electric car, and watts for always-on devices. Behind each row sits a typical energy figure (for example 0.8 kWh per 40 °C wash, 0.75 kWh per day for an A–C rated fridge-freezer, 0.19 kWh per km for an EV including charging losses). The calculator turns these into kWh per month and ranks the appliances so you can see what really drives the bill.

The tariff section supports the three structures used by most utilities worldwide:

• Flat rate: one price per kWh.
• Tiered (block) rates: a cheap first block, more expensive later blocks, common in the US, Asia and parts of southern Europe.
• Day/night (time-of-use): a cheaper off-peak price. If you leave the night share at 0, the calculator estimates it from your appliances: about 90% of EV charging, 80% of electric water heating, 50–60% of washing and dishwashing and a third of 24-hour loads fall into an 8-hour night window.

Finally it adds the standing charge, any levies billed separately, and VAT.

The formula

Worked example: the default household

The defaults describe a three-person household with gas heating: one fridge-freezer, 15 LED bulbs, four hours of TV, a desktop PC and a laptop, four washes, two dryer cycles and five dishwasher runs a week, an electric oven and hob, a kettle, a microwave, an hour of air conditioning per day on average, and 40 W of always-on devices.

That adds up to 233 kWh a month (2,793 kWh a year). At a flat €0.25/kWh the energy charge is €58.18, and the standing charge of €0.35/day adds €10.65, for a monthly bill of €68.83, or €826 a year. Because of the fixed charge, the average all-in price is €0.296/kWh, while each additional kWh costs only the €0.25 unit price.

The biggest single item is not a big appliance at all: always-on and standby loads (40 W around the clock, 350 kWh a year, 12.5%). Next come the tumble dryer (313 kWh), air conditioning (292 kWh), the fridge-freezer (274 kWh) and the dishwasher (261 kWh). Lighting, with LEDs, is only 6%.

How to read the results

• Monthly and annual bill are what you would pay including fixed charges and tax.
• Average all-in price divides the whole bill by kWh. It is useful for comparing tariffs, but it overstates the value of saving one kWh.
• Marginal price is what one extra kWh costs. Use it to judge savings from LED bulbs, efficient appliances or solar panels.
• The doughnut and table show each appliance’s share. Costs per appliance are allocated at your average energy price, excluding the standing charge, which you pay anyway.
• With a time-of-use tariff, the extra tile shows how much the night share saves compared with paying the day rate for everything.

Typical values

Tips to reduce your bill

• Attack the baseload first. Read your meter late at night with everything “off”; anything above 30–50 W is worth investigating with the standby power calculator.
• Dry clothes outside or switch to a heat-pump dryer. A heat-pump dryer uses about half the energy of a condenser or vented dryer.
• Use eco programmes. Dishwasher and washing-machine eco cycles run longer but at lower temperatures, cutting energy by 20–40%.
• Shift flexible loads if you have a time-of-use tariff: EV charging, water heating and appliances with a delay timer.
• Check individual appliances with the appliance energy cost calculator and size your cooling with the air conditioner calculator.
• Replace any remaining halogen bulbs. The LED savings calculator shows paybacks of a few months.

Limitations

Appliance energy figures are typical averages; the real consumption of an old fridge, a gaming PC or a vented dryer can be twice the default. Heating and air-conditioning hours are averaged over the year, so a single summer bill will be higher than the monthly average shown. Tiered tariffs are applied to the monthly total; some utilities use daily or seasonal blocks, demand charges or capacity fees, which are not modelled. Real bills may also include meter rental, renewable surcharges or social tariffs; add them as levies or to the standing charge.

Method & assumptions

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