{"id":732,"date":"2026-08-08T14:28:30","date_gmt":"2026-08-08T14:28:30","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=732"},"modified":"2026-08-08T14:28:32","modified_gmt":"2026-08-08T14:28:32","slug":"electricity-cost","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/electromagnetism\/electricity-cost\/","title":{"rendered":"Electricity Cost: kWh, Wattage and Rate Explained"},"content":{"rendered":"\n
Definition<\/div>

\n\nElectricity cost is the price you pay for the electrical energy an appliance consumes, calculated as Cost = kWh \u00d7 rate. Multiply the appliance’s power in kilowatts by the hours it runs to get kilowatt-hours, then multiply that by your tariff’s price per kilowatt-hour. Watts divided by 1000 gives kilowatts.\n\n<\/p><\/div>\n\n

Your kettle is rated 2000 W. The little box charging your headphones draws 5 W. One of them sounds expensive and one sounds trivial \u2014 and over a year, that instinct can be completely wrong.<\/p>\n\n

The bill doesn’t charge you for watts. It charges you for watts multiplied by time, and time is where the surprises hide. Once you can do that multiplication, every appliance in your home stops being a mystery and becomes a number you can predict.<\/p>\n\n

What Is Electricity Cost?<\/h2>\n\n

Electricity cost is the amount of money charged for the electrical energy a device uses, found by multiplying the energy consumed in kilowatt-hours by the price your supplier charges per kilowatt-hour.<\/p>\n\n

Think of your meter as a taxi. The watt rating is how fast the fare ticks; the hours are how long you sit in the cab. A fast meter for thirty seconds costs less than a slow meter running all week.<\/p>\n\n

That distinction \u2014 rate versus total \u2014 is the whole subject. Power<\/strong> (watts) is how quickly energy is transferred. Energy<\/strong> (kilowatt-hours) is how much has been transferred in total. You are only ever billed for the second one.<\/p>\n\n

A quick note on currency before the numbers start. Rates below are written as plain figures, so 0.20 per kWh means 20 cents, 20 pence, or 20 of whatever minor unit appears on your bill. The arithmetic is identical everywhere.<\/p>\n\n

The Electricity Cost Formula<\/h2>\n\n

The headline formula is short enough to memorise in one reading.<\/p>\n\n

Cost = kWh \u00d7 rate<\/div>\n\n

That version assumes you already know the kilowatt-hours. Most of the time you don’t \u2014 you have a wattage from a label and a rough idea of running time, so the working formula expands to this.<\/p>\n\n

Cost = (P \u00f7 1000) \u00d7 t \u00d7 r<\/div>\n\n

Every symbol, with its unit:<\/p>\n\n