Electricity costs: what an appliance costs to run
Every appliance in your home has a power rating in watts, and every electricity bill is built from kilowatt-hours. Knowing the link between the two lets you see exactly how much the kettle, heater, or air conditioner costs per day, per month, and per year. An electricity cost calculator turns wattage and usage habits into a concrete euro figure, making energy-saving decisions measurable rather than guessed.
TL;DR
- The power rating in watts is converted to kilowatts by dividing by 1000
- Formula: kWh per day = (Watts ÷ 1000) × Hours | Daily cost = kWh × Price per kWh | Mo
- Example 1: A 2,000 W heater used 3 hours a day
How it works
The power rating in watts is converted to kilowatts by dividing by 1000. The kilowatts are multiplied by the hours the appliance runs per day and by the electricity unit rate to obtain the daily cost, then scaled by the number of days to get monthly and yearly totals.
The math
Convert the appliance wattage to kilowatts, multiply by the daily usage hours to obtain daily energy in kWh, and multiply by the price per kWh to get the daily cost. Extend to the month and year by multiplying by 30 and 365 respectively, or by the exact number of days entered.
A 1,000-watt appliance running for one hour consumes exactly 1 kWh, which is the unit charged on every electricity bill.
Examples
Example 1: A 2,000 W heater used 3 hours a day
- Energy: 2 × 3 = 6 kWh/day
- At €0.25/kWh: €1.50/day
- Monthly: €1.50 × 30 = €45
- Heating dominates the winter bill
Example 2: A 100 W fridge running 24 hours (compressor cycle)
- Actual average draw: about 50 W due to cycling
- Energy: 0.05 × 24 = 1.2 kWh/day
- Yearly: 1.2 × 365 = 438 kWh
- At €0.25/kWh: about €109.50 per year
When to use it
✦ Energy Budgeting
Households identify the most expensive appliances and quantify the savings from usage changes, timers, and efficient replacements.
✦ Comparing Appliances
Buyers compare the running costs of energy classes before purchasing, adding the operating cost to the purchase price.
⚠ Common mistakes
- Using Rated Power for Intermittent Devices: Fridges, ovens, and air conditioners cycle; their average draw is far below the rated wattage.
- Forgetting Standby Consumption: Chargers and electronics in standby draw 1-10 W each, quietly adding several euros per month.
- Mixing Price Units: Rates are quoted per kWh, not per watt; dividing watts directly by the price yields absurd results.
FAQ (6)
What is a kWh?
A kilowatt-hour is the energy consumed by a 1,000 W device running for one hour; it is the standard unit on electricity bills.
How can I reduce my appliance costs?
Use timers, switch off standby devices, wash at lower temperatures, and replace old appliances with high-efficiency models.
If I type my salary or prices here, do you store them?
No — and that's deliberate. Everything runs locally in your browser, nothing leaves your device. We don't see your net salary, your margins, or the VAT numbers you test. For a finance tool that matters: you can run a quick check on a payslip or an invoice while on public Wi-Fi and close the tab knowing no trace is kept server-side.
Can I use it on the train without signal to check an invoice?
Yes. Load the page once, then it works offline. VAT, discount and mortgage math are all pure JavaScript — no API call. I often test it in airplane mode: open the mortgage page, type 250,000 at 4.5% for 25 years, you get the schedule instantly, even in a tunnel.
Can I file taxes with these results?
Use it as a fast sanity check, not as the final filing. Formulas are standard (e.g. Net = Gross / 1+VAT) and verified against official sources listed at the bottom, but rates and thresholds change — Italy's 22% vs Germany's 19%, or IRPEF brackets. For the actual declaration, double-check with your accountant or Agenzia delle Entrate / HMRC / IRS.
How do I send a calculation to my accountant?
Hit 'Share Link' under the results. It encodes the inputs in the URL — e.g. ?price=1200&vat=22 — so your accountant opens the exact same view, no screenshot needed. You can also copy the result with one tap and paste it into an email.