How much does your appliance cost to run?

What the Electricity Cost Calculator Does

This Electricity Cost Calculator estimates how much it costs to run an appliance based on three inputs: its power rating in watts (W), how many hours you use it, and the price you pay per kilowatt-hour (kWh). It returns the cost per day and a projected monthly total, so you can compare devices and spot the ones quietly inflating your bill.

It is useful for homeowners and renters checking a space heater or air conditioner, anyone comparing an old fridge against a newer model, and small businesses budgeting for always-on equipment. If a device has a wattage label and you know your electricity rate, you can price its electricity cost in seconds.

How It Works: The kWh Formula

Electricity is billed by the kilowatt-hour, which is the energy used by a 1,000-watt device running for one hour. The calculator first converts watts to kilowatts, then multiplies by hours and your rate:

Daily cost = (watts / 1000) x hours per day x price per kWh

Monthly cost = daily cost x 30

The division by 1,000 turns watts into kilowatts. Multiplying by hours gives kWh consumed, and multiplying by your price converts that energy into money. The monthly figure assumes a 30-day month for a simple, consistent estimate.

Worked Example With Real Numbers

Suppose you run a 1,500 W electric space heater for 5 hours a day and pay 0.30 per kWh.

Convert to kilowatts: 1500 / 1000 = 1.5 kW. Energy per day: 1.5 kW x 5 hours = 7.5 kWh. Daily cost: 7.5 x 0.30 = 2.25. Monthly cost: 2.25 x 30 = 67.50.

So that heater costs about 2.25 a day and roughly 67.50 over a 30-day month. Drop the runtime to 2 hours and the daily cost falls to 0.90 (1.5 x 2 x 0.30), or about 27 per month, showing how strongly usage hours drive the result.

Tips and Common Mistakes

A few small errors can throw the estimate off. Keep these in mind:

• Use the running wattage, not peak. Many appliances list a maximum or startup figure higher than their typical draw.
• Watch your rate units. Bills often quote cents per kWh; convert to the same unit you enter (for example, 30 cents = 0.30).
• Account for duty cycle. Fridges, freezers, and thermostatically controlled heaters cycle on and off, so they do not draw full power for every hour they are plugged in.
• Convert amps if needed. If a label shows only amps and volts, watts = volts x amps (e.g. 120 V x 5 A = 600 W).
• Remember the 30-day assumption. For an exact billing period, multiply the daily cost by the actual number of days.

Factors That Affect Your Real Bill

Your actual cost can differ from the estimate for several reasons. Tiered or time-of-use tariffs charge different rates depending on total consumption or time of day, so a flat per-kWh rate is an approximation. Standing charges, taxes, and grid fees are added separately on most bills and are not part of this appliance-level calculation.

Efficiency also matters: an aging motor or a heater fighting poor insulation works longer to do the same job, raising real-world kWh. For the most accurate figure, read your actual rate from a recent bill and, where possible, measure consumption with a plug-in energy monitor.