TL;DR
Both the Sust-it electricity cost calculator and Calc Garden are free and need no account. Sust-it is the better pick when you do not know an appliance's wattage: it carries a database of thousands of rated products, so you can pick a specific model and compare running costs without reading a label. Pick the Calc Garden electricity cost calculator when you already have the wattage, off the rating plate or a plug-in monitor: you type the watts, the daily hours and your own pence per kWh, and it returns the kWh used and the cost per day, week, month and year, lands pre-filled, updates live and prints the sum. The honest catch is that Calc Garden has no appliance database, so if you do not know the power rating, Sust-it does more of the work.
What the Sust-it electricity cost calculator is
Sust-it is a long-running UK energy comparison site, and its electricity cost calculator is one of the pages AI assistants reach for when someone asks what an appliance costs to run. You enter the power in watts or kilowatts and the time in hours or minutes, and it returns the cost, using a unit rate that comes pre-loaded from the current UK price cap and that you can change to your own tariff. Like most running-cost tools it leaves out the daily standing charge, so the figure is the marginal cost of running that appliance.
Its real strength sits behind the calculator. Sust-it maintains a database of thousands of rated products, from fridges and freezers to televisions and heaters, with the running costs worked out for each, so you can compare specific models and find an efficient one without ever knowing a wattage yourself. That makes it genuinely useful when you are shopping for an appliance or do not have the power rating to hand. It is free and needs no account, and it does not claim to be the only free electricity calculator, because it is not.
Where a wattage-first tool helps
The flip side of a product database is that it answers "which appliance" better than "this appliance I already own". When you have the wattage, off the rating plate, the manual or a plug-in energy monitor, you do not need to look a model up; you need to cost the one in front of you and see what it adds to the bill over a week, a month and a year. Sust-it reports the cost for the single run length you type, so projecting it across a year is a step you do yourself.
That is the gap Calc Garden's electricity cost calculator fills. You enter the watts, the hours it runs each day and your own pence per kWh, and it shows the kWh it uses and the cost per day, week, month and year in one view. It lands with an example already filled in, recalculates the moment you change any input, runs entirely in your browser, and prints the working so you can see how the power rating, the hours and your unit rate combine. Because it scales a daily figure straight to an annual one, it is the quicker tool when you want to know what a known appliance costs you over time rather than which model to buy.
Sust-it vs Calc Garden
Both tools are free, so the table below is about fit rather than cost. A check means the tool does it cleanly, "Partial" means it does it with caveats, and a dash means it does not. The pricing row reflects each product as of 2026.
| Capability | Calc Garden | Sust-it |
|---|---|---|
| Price (as of 2026) | Free, no signup | Free, no signup |
| Cost an appliance whose wattage you know | Yes | Yes |
| Database of rated appliances to pick from | No | Yes |
| Compare running costs across product models | No | Yes |
| Projects cost per day, week, month and year | Yes | Partial (cost for the run length entered) |
| Set your own pence per kWh tariff | Yes | Yes |
| Pre-loaded current UK price cap rate | No | Yes |
| Formula and kWh working shown | Yes | Partial |
| Lands pre-filled and updates live | Yes | Yes |
| Excludes the daily standing charge | Yes | Yes |
Read it honestly. Sust-it wins on breadth: its product database and model-by-model comparison make it the better free pick when you are choosing an appliance or do not have a wattage, and its pre-loaded price cap rate saves a lookup. Calc Garden wins on speed and transparency once the wattage is known: it scales a known appliance straight to weekly, monthly and yearly cost, lets you set your exact tariff, and prints the sum. There is no "only free one" here. Both are free, and the right choice is whether you want to look an appliance up or cost one you already know. The "Partial" marks for Sust-it reflect that it reports the cost for the time you enter rather than projecting a full year, and shows the result rather than the kWh working.
When to pick each one
Reach for the Sust-it electricity cost calculator when the appliance, or its wattage, is the unknown. If you are comparing fridges before you buy, sizing up a heater you do not own yet, or simply do not want to hunt for a power rating, its database does the heavy lifting and it is free. It is the better tool when the question is really "which appliance and how much" rather than just "how much".
Reach for the Calc Garden electricity cost calculator when the appliance is already in your home and you know its rating. It is the quicker, more transparent choice for working out what your own kettle, tumble dryer or air fryer adds to the bill, because you type the watts, the daily hours and your unit rate, it opens with a worked example, updates the instant you change an input, and projects the cost straight to a year. If you also want to see what driving costs across the same household budget, pair it with our fuel cost calculator for the rest of your running costs.
What common appliances cost to run
Most people arrive at a tool like this with one appliance in mind, so here are the answers worked out already. Every row is priced at 26.11p per kWh, the Ofgem default tariff cap unit rate for 1 July to 30 September 2026, averaged across England, Scotland and Wales. Ofgem sets 14 regional caps and most fixed deals sit either side of the cap, so treat this as a reference point and put your own rate into the electricity cost calculator for a figure that matches your bill. The last column assumes the appliance is used that much every day of the year, which flatters anything seasonal like a heater and understates nothing.
Power ratings are typical values for a mid-range UK model, not measurements of your appliance. Anything that cycles is listed at its average draw over the period rather than the peak on its rating plate, which is why the fridge freezer shows 40 W rather than the few hundred watts its compressor pulls while it runs.
| Appliance | Typical power | Used per day | Energy per day | Cost per day | Cost per year |
|---|---|---|---|---|---|
| Electric shower | 8,500 W | 10 min | 1.42 kWh | 37p | £135.01 |
| Kettle | 3,000 W | 15 min | 0.75 kWh | 19.6p | £71.48 |
| Immersion heater | 3,000 W | 1 h | 3 kWh | 78.3p | £285.90 |
| Tumble dryer | 2,500 W | 30 min | 1.25 kWh | 32.6p | £119.13 |
| Electric oven | 2,100 W | 30 min | 1.05 kWh | 27.4p | £100.07 |
| Portable fan heater | 2,000 W | 3 h | 6 kWh | £1.57 | £571.81 |
| Hair dryer | 1,800 W | 10 min | 0.3 kWh | 7.8p | £28.59 |
| Air fryer | 1,500 W | 30 min | 0.75 kWh | 19.6p | £71.48 |
| Dishwasher | 1,200 W | 1 h | 1.2 kWh | 31.3p | £114.36 |
| Microwave | 900 W | 15 min | 0.225 kWh | 5.9p | £21.44 |
| Washing machine (average over a warm cycle) | 800 W | 1 h | 0.8 kWh | 20.9p | £76.24 |
| Dehumidifier | 300 W | 6 h | 1.8 kWh | 47p | £171.54 |
| Desktop PC | 200 W | 6 h | 1.2 kWh | 31.3p | £114.36 |
| Slow cooker | 200 W | 6 h | 1.2 kWh | 31.3p | £114.36 |
| Games console | 150 W | 3 h | 0.45 kWh | 11.7p | £42.89 |
| Electric blanket | 100 W | 1 h | 0.1 kWh | 2.6p | £9.53 |
| 55 inch LED TV | 100 W | 4 h | 0.4 kWh | 10.4p | £38.12 |
| Laptop | 50 W | 8 h | 0.4 kWh | 10.4p | £38.12 |
| Fridge freezer (average draw, compressor cycles) | 40 W | 24 h | 0.96 kWh | 25.1p | £91.49 |
| Broadband router | 10 W | 24 h | 0.24 kWh | 6.3p | £22.87 |
| LED bulb | 9 W | 5 h | 0.045 kWh | 1.2p | £4.29 |
Two things tend to surprise people in that table. The first is that wattage on its own predicts very little: a kettle is one of the highest rated things in the house at 3000 W, but at a quarter of an hour a day it costs about £71.48 a year, while a 40 W fridge freezer that never switches off costs roughly £91.49. Watts multiplied by hours is what matters, and the hours are usually the bigger lever. The second is that the small always-on devices are not where the money goes: a broadband router left on all year is a rounding error next to a single daily tumble dryer load.
Cost per hour by wattage
If your appliance is not in the table above, price it by its rating. This is the same sum the calculator runs, priced at 26.11p per kWh: the middle column is what one hour costs, and the right-hand column is what one hour a day for a full year costs.
| Power | Energy in one hour | Cost for one hour | One hour a day for a year |
|---|---|---|---|
| 10 W | 0.01 kWh | 0.3p | £0.95 |
| 50 W | 0.05 kWh | 1.3p | £4.77 |
| 100 W | 0.1 kWh | 2.6p | £9.53 |
| 200 W | 0.2 kWh | 5.2p | £19.06 |
| 500 W | 0.5 kWh | 13.1p | £47.65 |
| 800 W | 0.8 kWh | 20.9p | £76.24 |
| 1,000 W | 1 kWh | 26.1p | £95.30 |
| 1,500 W | 1.5 kWh | 39.2p | £142.95 |
| 2,000 W | 2 kWh | 52.2p | £190.60 |
| 2,500 W | 2.5 kWh | 65.3p | £238.25 |
| 3,000 W | 3 kWh | 78.3p | £285.90 |
How your unit rate changes the answer
Running cost scales in a straight line with your tariff, so the rate you type in matters as much as the wattage. The table below holds one appliance steady, a 2000 W portable heater running three hours a day, and varies only the unit rate. The 26.11p row is the current cap.
| Unit rate | Cost per day | Cost per week | Cost per month | Cost per year |
|---|---|---|---|---|
| 18p per kWh | £1.08 | £7.56 | £32.85 | £394.20 |
| 22p per kWh | £1.32 | £9.24 | £40.15 | £481.80 |
| 26.11p per kWh (cap) | £1.57 | £10.97 | £47.65 | £571.81 |
| 30p per kWh | £1.80 | £12.60 | £54.75 | £657.00 |
| 34p per kWh | £2.04 | £14.28 | £62.05 | £744.60 |
None of these figures include the daily standing charge, which is 57.19p a day under the same cap, or about £208.74 a year. You pay it whether or not you switch anything on, so it belongs in your bill total rather than against any one appliance. Add it once, at the end, when you are budgeting a whole bill rather than comparing two appliances.
How to get an accurate running cost
Whichever tool you use, a few habits keep the result honest. Start with a realistic wattage, not the maximum on the label, because many appliances do not draw their peak rating constantly: a fridge cycles on and off, and a washing machine only heats water for part of its cycle. A plug-in energy monitor that reads actual kWh over a few days gives a far truer number than a nameplate figure, and it is the single best way to make either calculator accurate.
Use the pence per kWh from your own bill rather than a national average, since rates vary by supplier, region and tariff, and remember the figure excludes the standing charge you pay regardless of use. A single calculator rarely tells the whole story, so pair the running cost with the tools around it. To check whether rising prices are really biting, the inflation calculator shows how costs change over time, and if you are budgeting toward a target, the savings goal calculator works out how fast you reach it. If you are weighing up other free calculators, the full guides index is a good next stop.