How to Check Appliance Power Consumption and Calculate Running Costs

To estimate an appliance's running cost, find its power rating in watts (W) on the label or in the manual, convert that to kilowatt-hours (kWh) using the hours you actually use it, then multiply by your electricity tariff. For example, a 2,000 W heater run for 3 hours uses 6 kWh; at 30p per kWh that is about £1.80. This method works for any mains appliance and lets you compare similar models before buying. Sust-it's energy calculators and appliance databases are built around exactly this kind of comparison, alongside its running-cost data for electricals and vehicles.

Step 1: Find the power rating in watts

Check, in this order:

• Rating plate or sticker — usually on the back, base, or inside the door of the appliance. Look for "W", "watts", or "Wattage".
• Manual or spec sheet — often gives a range (e.g. 1,800–2,200 W) rather than a single figure.
• Energy label — for large appliances this gives annual kWh directly, which skips the maths below.

Two complications to watch for:

• Ranges and cycles. Washing machines, dishwashers, and ovens draw different power at different stages. Use the label's maximum for a worst case, or the energy label's annual kWh for a realistic average.
• Standby and always-on loads. Devices left on standby or running 24/7 (routers, set-top boxes, fridges) need their hours counted across the whole day, not just active use.

Step 2: Convert watts and hours into kWh

The formula:

kWh = (watts ÷ 1,000) × hours used

Worked examples:

For appliances you only use seasonally, multiply daily kWh by the number of days you actually use them rather than 365.

Step 3: Multiply by your electricity tariff

Running cost = kWh × price per kWh

Your price per kWh is on your bill or tariff summary. Using 30p/kWh as an illustration:

• LED bulb: 18 kWh/year × £0.30 ≈ £5.40/year
• Laptop: 142 kWh/year × £0.30 ≈ £43/year
• Fan heater at 3 h/day for a winter month (90 kWh) × £0.30 ≈ £27/month

Heating and cooling appliances dominate because their wattage is high and their run times are long. Lighting and small electronics are usually minor by comparison — Sust-it notes that lighting accounts for roughly 10–20% of a typical home's electricity bill, which is why switching to low-energy and LED bulbs is a common first step.

Step 4: Compare similar appliances before buying

Running-cost comparison only makes sense between appliances that do the same job. Use the same three inputs — rated power, realistic hours, tariff — for each candidate. Sust-it's appliance and technology databases list power ratings and running costs across categories, and its electricity cost calculators let you plug in your own usage and tariff rather than relying on averages.

A practical comparison: two kettles with the same capacity but different wattages. The higher-wattage one boils faster but uses broadly similar energy per boil; the bigger saving usually comes from boiling only the water you need, not from the wattage alone. This is why comparing kWh per task beats comparing watts in isolation.

Step 5: Target the high-consumption appliances

Rank your appliances by annual kWh from Step 2. The top of the list is where changes pay off:

• Heating and cooling — the largest loads; reducing run time, improving insulation, or choosing a more efficient model has the biggest effect.
• Wet appliances (washing machines, dishwashers, tumble dryers) — use full loads, lower-temperature cycles, and air-dry where possible.
• Refrigeration — runs continuously, so siting away from heat sources and keeping seals clean matters more than short-term habits.
• Standby loads — switch off at the plug where practical.

Common sticking points

• Using maximum wattage for everything overstates cost for cycling appliances; use the energy label's annual kWh where available.
• Forgetting the tariff includes standing charges — the per-kWh figure is what you multiply by, not the total bill divided by kWh.
• Assuming a higher wattage always costs more — run time usually matters more than the rating.
• Ignoring how you use the appliance — the same model can differ widely in annual cost depending on loads, cycles, and settings.

Once you have a ranked list in kWh and pounds, you can decide what to replace, what to run less, and what to leave alone.