Practical energy guide
How to read an appliance energy label
Use the label’s kWh figure with the period or test basis printed beside it. A letter class alone does not tell you the household running cost.
Start with the stated unit
Labels can show kWh per 100 cycles, per cycle, per year or per 1,000 hours. Preserve that basis when converting. For 52 cycles from a per-100-cycles figure, divide by 100 and multiply by 52.
Keep units attached to every number. Watts describe power, while kWh describe energy. The calculators apply the unit rate in pence per kWh and show pounds or pence without hiding the conversion.
Efficiency class and size
The efficiency scale helps compare products in the same label category, but a larger efficient appliance can still use more total energy than a smaller one. Compare capacity, programme and energy figure together.
Test conditions
Label values come from specified standard procedures. Your programme, load, room temperature or viewing settings may differ. Treat the figure as a consistent comparison point rather than a prediction guaranteed for every home.
Real use can vary by model, settings, condition and household routine. Test more than one reasonable scenario when a single assumption drives the answer. That range is more useful than reporting an over-precise total.
Useful category details
Washers and dishwashers may refer to an eco programme. Refrigeration normally gives annual consumption. Displays may provide energy for a fixed number of hours. Read the icon labels and product documentation before converting.
A comparison example
If one dryer states 180 kWh per 100 cycles and another states 230, their label-cycle figures are 1.8 and 2.3 kWh. Multiply by your expected cycles and tariff, then consider purchase cost and whether the programmes meet the same need.
Applying this guide to your household
Start with the best source available: the product’s electrical input, an energy-label kWh value, the manual, or a safe representative measurement. Match the unit and period in the calculator. Enter your own tariff rather than a quoted national average, and keep the standing charge separate.
Check the live calculation breakdown after submitting. It repeats your inputs and shows how energy becomes cost. Save clearly labelled results to the basket, where you can change the tariff and compare each item’s share of the saved total. The basket does not send the data to this website.
If a comparison involves purchasing equipment, separate energy arithmetic from the financial decision. Purchase, delivery, installation, disposal, maintenance and ownership period can change payback. Repairability, suitability and safety are also relevant even though they are not converted into money here.
Checking whether the result is reasonable
Sense-check the order of magnitude before acting. A very high wattage used for only a few minutes may consume less energy than a modest load left running all day. Compare the calculated annual kWh with the period and frequency entered, and make sure pence were not entered as pounds or vice versa.
Run a low, central and high scenario when duration or cycling is uncertain. Record why each assumption was chosen. If a monitored figure is available, measure a complete representative programme or several ordinary days rather than selecting an unusually light session. Seasonal equipment needs observations from conditions similar to those being estimated.
Finally, distinguish the appliance estimate from the household bill. The bill can include every electrical load, standing charge, tariff changes, corrections and account adjustments. A difference does not automatically mean the formula is wrong; first compare the same time period, tariff basis and set of loads.
Limitations and assumptions
Results are estimates based on the information entered. Actual energy use can vary by appliance model, settings, temperature, cycling, condition and household behaviour. The calculation cannot predict future tariffs, repairs or behavioural changes. It estimates electricity only and does not include gas, water, detergent or the daily electricity standing charge unless a page explicitly says otherwise.
Examples explain the maths and are not claims about every appliance. This information is general, not electrical, installation, medical or financial advice. Follow manufacturer instructions and obtain appropriately qualified help where a safety-critical decision requires it.
Common questions
Frequently asked questions
Does a better letter always cost less?
Not necessarily; size and use also matter.
Can I use annual kWh directly?
Yes, choose annual-energy mode.
Why does my monitor differ?
Your conditions and programme may differ from the label test.
Put it into practice
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