Smart Meter / Appliance Cost Calculator

A smart meter sends automatic readings to your energy supplier, eliminating estimated bills and giving you accurate real-time data on your energy usage. The in-home display (IHD) shows your spending in pounds and pence, making it easier to identify wasteful habits and reduce consumption. Smart meters are provided free of charge by your supplier. Two generations are in circulation, SMETS1 meters being the older type, some of which lose smart functionality if you switch supplier, and SMETS2 the current standard that works with all suppliers. The original aim of offering every home a smart meter by 2020 slipped, and since 2022 suppliers have worked to binding annual installation targets instead, reaching for roughly three-quarters of homes by the end of 2025. The rollout stands at about 70%.

Research by the Department for Energy Security and Net Zero suggests smart meter users reduce their electricity consumption by 2 to 4% and gas consumption by 3 to 5% through better awareness. For an average household, this translates to savings of £40 to £90 per year. The biggest savings come from identifying and reducing standby consumption and unnecessary heating. Devices that draw power around the clock, a television left on standby or a broadband router, account for £30 to £80 a year between them.

This calculator works out what individual appliances cost to run: set your electricity unit rate and the hours each device is used, and it shows the daily cost per appliance and in total, which is the kind of breakdown a smart meter's in-home display makes visible. Two further benefits are harder to model but perfectly real. A meter reporting actual readings stops the estimated Direct Debit drifting away from what you owe, which is worth £50 to £200 a year in over or underpayment. Watching the daily figure also exposes a failing appliance early, since a faulty fridge can draw 2 to 3 times what it should long before it stops working altogether.

Smart meters also enable access to time-of-use tariffs that charge different rates at different times of day. Octopus Agile prices every half hour against the wholesale market, usually 10 to 25p per kWh, and occasionally goes negative so that you are paid to use electricity. Octopus Tracker sets a daily rate on the same wholesale basis, while Octopus Cosy, aimed at heat pumps, has 3 tariff periods with the cheapest running 4am to 7am and 1pm to 4pm. The legacy Economy 7 rate of 8 to 10p per kWh between 11pm and 6am still suits storage heaters.

Shifting usage is where the money sits. Moving more than half your consumption off-peak can take 20 to 30% off the bill, which is why these tariffs suit overnight EV charging, heat pumps with thermal storage and scheduled appliance use. Filling a car battery overnight costs £7 to £10 against about £30 in the middle of the day. Running dishwashers and washing machines at night works on the same principle, though the saving depends entirely on how much of your load you can genuinely move.

Installation is free and usually takes 1 to 2 hours, with the installer fitting new gas and electricity meters plus the in-home display. Power goes off briefly during the gas swap, so pilot lights on older water heaters may need relighting afterwards. There is no ongoing cost, and nobody should be charging you for the work, because it comes from your supplier. Very old fuse boxes occasionally need a consumer unit upgrade first at £300 to £600, and converting a prepayment meter takes a separate appointment.

Turning the installer away is a legal right, though a supplier may charge slightly higher rates for manual readings. Smart meters collect half-hourly readings routed through the Data Communications Company, so your supplier can see the shape of your usage, and you can opt out to daily readings instead. On radio emissions, a smart meter puts out far less than a mobile phone or a Wi-Fi router, and Public Health England, now the UK Health Security Agency, has confirmed no health risk.