How to Calculate Appliance Electricity Cost UK

The Electricity Cost Formula

The basic formula works for any electric appliance: convert watts to kilowatts, multiply by hours, then multiply by your rate.

Every electric appliance has a wattage rating, which tells you how much power it consumes [S1]. This is usually printed on a label on the appliance, listed in the manual, or visible on your energy monitor. Common examples: kettle 2,000-3,000W, laptop 30-60W, fridge 100-200W.

To calculate cost, use this three-step formula: Step 1: Divide the wattage by 1,000 to convert to kilowatts. Step 2: Multiply by the number of hours the appliance is on. Step 3: Multiply by your electricity rate in pence per kWh. The result is the cost in pence.

• Step 1: Watts ÷ 1,000 = kilowatts (kW)
• Step 2: kW × hours = kilowatt-hours (kWh)
• Step 3: kWh × pence per kWh = cost in pence
• Convert pence to pounds by dividing by 100
• Standing charges are excluded from the calculation [S1]

Finding Your Appliance Wattage

Wattage is printed on the appliance label, listed in the manual, or measured by an energy monitor.

The easiest way to find an appliance's wattage is to look at the label on the back or bottom of the appliance [S1]. This label shows the maximum wattage the appliance uses. For multi-setting appliances (like washing machines with different cycles), the label usually shows the maximum wattage for the most power-intensive setting.

If the label is missing or unreadable, check the manual or search for the model number online. Alternatively, use a plug-in energy monitor, which measures actual wattage in real time [S3]. These are available for £15-30 and are useful for measuring multiple appliances.

• Check the label on the back or bottom of the appliance
• Read the manual or search the model number online
• Use a plug-in energy monitor for real-time measurements [S3]
• Smart meters show whole-home consumption in real time
• Appliance wattage may vary by setting or mode

Using Your Actual Electricity Rate

Your actual electricity rate may differ from the headline Ofgem cap rate. Check your bill for the accurate figure.

The Ofgem energy price cap sets a maximum unit rate, but your actual rate depends on your tariff [S2]. Standard variable tariffs are typically at or near the cap rate. Fixed tariffs may be higher or lower depending on when you locked in. Economy 7/10 tariffs offer cheaper off-peak rates (typically 15-20p per kWh) but higher peak rates.

To find your actual rate, check your latest electricity bill or log into your energy supplier's online account [S2]. Look for the 'unit rate' or 'price per kWh' figure. If you have a smart meter, your in-home display should show the current rate.

• Check your electricity bill for the unit rate in pence per kWh
• Standard variable tariffs: typically at or near the Ofgem cap rate
• Fixed tariffs: may differ from the cap rate
• Economy 7/10: cheaper off-peak (15-20p/kWh), higher peak rate
• Smart meter in-home display shows current rate

Practical Calculation Examples

Here are worked examples showing how to calculate the cost of common household appliances.

Example 1: Kettle. A 3,000W kettle boiling for 5 minutes. Convert time: 5 minutes = 0.083 hours. Calculation: 3.0 × 0.083 × 26.32 = 65.6p per boil. Example 2: Tumble dryer. A 2,500W dryer running for 1 hour. Calculation: 2.5 × 1 × 26.32 = 65.8p per hour.

Example 3: TV. A 100W TV on for 5 hours. Calculation: 0.1 × 5 × 26.32 = 13.16p per evening. Example 4: Washing machine. A 2,000W machine on a 2-hour cycle. Calculation: 2.0 × 2 × 26.32 = £1.05 per wash. Note: washing machines also heat water, so actual consumption varies by programme and water temperature.

• Kettle (3kW, 5 min): 3.0 × 0.083 × 26.32p = 65.6p
• Tumble dryer (2.5kW, 1 hour): 2.5 × 1 × 26.32p = 65.8p
• TV (100W, 5 hours): 0.1 × 5 × 26.32p = 13.16p
• Washing machine (2kW, 2 hours): 2.0 × 2 × 26.32p = £1.05
• Always convert minutes to hours by dividing by 60

Understanding Standing Charges

Standing charges are daily fixed fees payable regardless of how much electricity you use and are excluded from appliance cost calculations.

A standing charge is a fixed daily fee that your energy supplier charges for maintaining your gas and electricity supply [S1]. This is typically 50-60p per day for electricity and is payable whether you use any electricity or not. Because it is a fixed cost, it should not be included when calculating the running cost of individual appliances.

The standing charge covers the cost of maintaining the electricity network, meter readings, and supplier overheads [S2]. While it affects your total energy bill, it does not affect the relative cost of running different appliances. An appliance that uses more electricity will always cost more to run, regardless of the standing charge.

• Standing charge: typically 50-60p per day for electricity
• Payable regardless of electricity use [S1]
• Excluded from appliance cost calculations
• Affects total bill but not relative cost of appliances
• Included in your annual energy cost, not per-appliance cost

Using Energy Monitors and Smart Meters

Energy monitors and smart meters provide real-time data on appliance consumption for accurate cost tracking.

A plug-in energy monitor clips onto your electricity cable and displays the real-time wattage consumption of individual appliances [S3]. This is useful for measuring actual consumption rather than relying on label wattage, which may not reflect real-world usage.

Smart meters provided by energy suppliers show your whole-home electricity consumption in real time on an in-home display [S3]. While they do not break down consumption by individual appliance, they provide accurate data on total usage and can help you identify high-consumption periods.

• Plug-in energy monitors: £15-30, measure individual appliance consumption [S3]
• Smart meters: provided free by energy suppliers, show whole-home consumption
• Clip-on energy monitors: attach to mains cable, good for whole-home monitoring
• Some smart plugs include energy monitoring features
• Use real-time data to identify wasteful consumption patterns

Frequently asked questions

Bottom line

Calculating appliance electricity costs is straightforward: (Watts ÷ 1,000) × hours × your rate per kWh. Find your appliance's wattage on its label or with an energy monitor, use your actual electricity rate from your bill, and exclude standing charges. This formula works for any electric appliance and helps you identify the most expensive items to run in your home.