The appliance
The currency is whatever you enter per kWh. Assumes a constant draw — appliances with thermostats cycle and use less.
Watts × hours is the whole calculation
A 1,500 W heater running 8 hours uses 12 kWh a day; an 8 W LED bulb over the same 8 hours uses 0.064 kWh. Multiply by your price per kWh and you have the cost — per day, and from there per month and year. The ratio of wattages is the ratio of costs, which is why anything that makes heat dominates the bill.
Your price per kWh is on your bill, nowhere else
Electricity prices differ by country, by utility, and often by time of day or usage tier. The honest number is your own bill: divide the total amount by the kWh billed and you get your effective price, fixed charges included. That figure is what makes the yearly cost here real rather than hypothetical.
The label wattage is a ceiling, not a steady draw
Fridges, air conditioners and heaters cycle on and off around a target temperature — "on for 8 hours" rarely means 8 hours at full power. For those, the result here is an upper bound; a plug-in energy meter or the annual consumption printed on the label gets closer to the truth. A kettle or a hair dryer, by contrast, really does draw its full rating whenever it runs.
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Frequently asked questions
Q. What do I enter as the price per kWh?
Read it off your electricity bill — no number here would survive crossing a border, and even neighbours on different tariffs pay differently. For a quick effective rate, divide the bill total by the kWh consumed; that folds fixed charges and taxes into one honest per-kWh price.
Q. Does standby power actually matter?
One box drawing 5 W around the clock uses about 44 kWh a year — enter 5 W and 24 hours here to see it in your money. A single device is small; a shelf of set-top boxes, consoles and chargers becomes a steady, silent line on the bill.
Q. Why does a heater cost hundreds of times what an LED does?
Making or moving heat takes kilowatts; running electronics takes watts. A 2,000 W heater against an 8 W bulb is a factor of 250 at identical hours. That is also where the savings are: one degree less heating outweighs any amount of light-switch discipline.