Appliance Energy Cost Calculator

How it is calculated

The tool converts watts to kilowatt-hours over the whole period and prices them: energy (kWh) = power (W) ÷ 1000 × hours per day × days, then cost = energy × rate per kWh and daily cost = cost ÷ days. Power is the wattage on the appliance label, hours is the daily running time, and the rate is the price of one kWh on your bill. If you leave Days empty or set it to zero or below, the tool assumes 30 days, so the total is then a monthly estimate. Power and hours must be above zero, hours cannot exceed 24 because a day has no more, and the rate cannot be negative; any of these breaking the rule, or a missing rate, gives no result. Energy is shown with one decimal, money with two, in the tool's default currency.

Common mistakes

• Entering kilowatts in the watts box. A 1.8 kW heater must be typed as 1800, otherwise the cost comes out a thousand times too low.
• Entering the weekly or monthly hours in the Hours per day box. The field expects hours per day (24 at most) and then multiplies by the number of days, so a value such as 40 shows no result.
• Treating the label wattage as an average. A fridge, a thermostat-controlled heater or an air conditioner cycles on and off, so its real daily use is well below full power times 24 hours. Enter the hours it actually draws power.
• Using a rate that is not per kWh, for example a monthly standing charge or a price per 100 kWh. The rate box is the price of one kilowatt-hour.
• Leaving Days blank and reading the total as a yearly cost. With no value the tool uses 30 days, so the total covers one month.