Energy Label Calculator: How to Read & Compare

An energy label calculator works out the annual energy consumption, running cost, or energy efficiency class of an appliance from its power rating, usage hours, and local electricity price. You enter the wattage, how many hours per day you use the device, and the cost per kilowatt-hour, and the calculator returns the yearly energy use in kWh and the estimated annual cost. The result helps you compare appliances and decide whether a more expensive, efficient model pays off over time.

Formula

The core formula behind the calculator is simple:

Annual energy (kWh) = (Power in watts / 1000) × hours per day × days per year

Then, annual cost = annual energy × electricity price per kWh.

Variables:

• Power rating (W) – the electrical power the appliance draws, usually printed on the label or in the manual.
• Daily use (hours/day) – how many hours per day the appliance runs on average.
• Days per year – often 365, but for seasonal items (like a heater) you might use 120 or 180.
• Electricity price (per kWh) – your local rate, which you can find on your bill.

The result is the annual running cost in your currency and the annual energy consumption in kWh.

Worked Example

Using the default values from the calculator:

• Power rating: 1500 W
• Daily use: 3 hours
• Days per year: 365
• Electricity price: 0.15 per kWh

Step 1: Convert watts to kilowatts: 1500 W ÷ 1000 = 1.5 kW

Step 2: Annual energy = 1.5 kW × 3 h/day × 365 days = 1642.5 kWh/year

Step 3: Annual cost = 1642.5 kWh × 0.15 = 246.375

The calculator rounds the cost to two decimals: 246.38. The energy is shown with one decimal: 1642.5 kWh.

How to Use an Energy Label Calculator

To get a useful result, you need three pieces of information:

1. Power rating – look for the wattage on the appliance’s nameplate or in the user manual. It might be listed as “Powerâ€� or “Consumptionâ€�.
2. Daily usage – estimate how many hours per day you actually use the device. For example, a fridge runs 24/7, but a kettle might only run 10 minutes.
3. Electricity price – check your energy bill for the cost per kWh. In many countries this is between 0.10 and 0.30, but it varies widely.

Once you have these, the calculator gives you the annual cost. You can compare two appliances by entering their respective power ratings and usage patterns.

Understanding the EU Energy Label

Since March 2021, the European Union uses a rescaled energy label with classes from A to G. A is the most efficient, G is the least. The label also shows the energy consumption in kWh per 1000 hours for appliances like TVs, or per cycle for washing machines.

An energy label calculator can convert these figures into a yearly cost. For example, a TV rated 100 W that runs 5 hours a day uses 0.1 kW × 5 h × 365 = 182.5 kWh per year. At 0.20 per kWh, that’s 36.50 per year.

Note that the label’s kWh figures are based on standard test conditions, not your actual usage. Real-world consumption may differ.

Common Mistakes and Misconceptions

One common mistake is confusing watts with kilowatt-hours. Watts measure power (the rate of energy use), while kilowatt-hours measure energy (the total amount used). A 1000 W appliance running for 1 hour uses 1 kWh, but running for 2 hours uses 2 kWh.

Another error is using the wrong electricity price. Some people use the price per kWh including taxes and standing charges, but the calculator only needs the per-unit cost. Also, be careful with units: if the power is given in kilowatts (kW), don’t divide by 1000 again.

Finally, don’t forget that some appliances have variable power. For example, a microwave might use 1000 W at full power but only 500 W when defrosting. Use an average or the most common setting.

Limitations of the Calculator

The calculator assumes constant power and constant usage every day. Real appliances may have standby power, which adds to consumption. A TV in standby mode can use 1–5 W, which over a year adds up to 8.8–43.8 kWh.

Also, the electricity price you enter is an average. If you have a time-of-use tariff, your cost per kWh varies by time of day. The calculator gives a rough estimate, not a precise bill.

For appliances like washing machines or dishwashers, the energy label gives consumption per cycle, not per hour. To use the calculator, you would need to estimate cycles per year and multiply by kWh per cycle, then multiply by the price.

Frequently Asked Questions

How do I find the power rating of my appliance?

Look for a metal or plastic plate on the back or bottom of the device. It usually lists the voltage, wattage, and model. If not, check the user manual or the manufacturer’s website. Some appliances, like refrigerators, list the power in watts but also have a separate energy label with annual kWh.

What is a good electricity price to use?

Use the price per kWh from your latest electricity bill. It’s usually listed under “unit rateâ€� or “energy chargeâ€�. If you don’t have a bill, you can use the average for your country, but that may not reflect your actual tariff.

Can I use this calculator for a washing machine?

Yes, but you need to convert the per-cycle consumption to an annual figure. If the label says 0.8 kWh per cycle and you do 200 cycles per year, that’s 160 kWh per year. Enter the power as 160,000 W (which is unrealistic) – instead, you should calculate the cost directly: 160 kWh × price per kWh. The calculator here is designed for continuous-use appliances, but you can adapt it by entering the daily equivalent.

Why does the calculator show a different result than my energy label?

Energy labels use standardized test conditions (e.g., a certain number of cycles or a standard load). Your actual usage may be higher or lower. Also, the label might give consumption per year directly, while the calculator estimates from power and time. If you already have the annual kWh from the label, you don’t need this calculator – just multiply that by your price.

Does a higher energy efficiency class always save money?

Not always. A more efficient appliance (e.g., class A vs. class C) uses less energy for the same task, but it may cost more to buy. To decide, compare the price difference with the annual savings. For example, if an A-rated fridge costs 100 more but saves 20 per year, it pays back in 5 years.

What about standby power?

Standby power is the electricity used when the appliance is off but still plugged in. Many devices use 1–5 W in standby. To include this, add the standby watts to your calculation. For example, a TV that uses 100 W on and 2 W standby, if on 5 hours and standby 19 hours, the daily energy is (100×5 + 2×19)/1000 = 0.538 kWh. You can enter the average power over 24 hours.

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in p | Power rating | W | 1500 | 0
in h | Daily use | hours/day | 3 | 0
in d | Days per year | days | 365 | 0
in c | Electricity price | per kWh | 0.15 | 0
out cost | Annual running cost | currency/year | (p/1000) * h * d * c | 2
out energy | Annual energy use | kWh/year | (p/1000) * h * d | 1