Turn a smart plug power reading into daily energy use and the monthly and annual cost of whatever is plugged into it.
Power in watts times hours of operation gives watt-hours; dividing by 1,000 converts to the kilowatt-hours your bill is denominated in. Carbon is estimated at roughly 0.4 kg CO2e per kWh, a mid-range grid intensity. An always-on appliance looks trivial at 10 W until it is multiplied by 8,760 hours — running cost, not purchase price, dominates the lifetime total.
Smart Plug Energy Cost
kWh = watts × hours ÷ 1,000; cost = kWh × tariff
kWh = watts × hours ÷ 1,000; cost = kWh × tariff Power in watts times hours of operation gives watt-hours; dividing by 1,000 converts to the kilowatt-hours your bill is denominated in. Carbon is estimated at roughly 0.4 kg CO2e per kWh, a mid-range grid intensity.
An always-on appliance looks trivial at 10 W until it is multiplied by 8,760 hours — running cost, not purchase price, dominates the lifetime total.
This calculator takes 4 inputs: Measured appliance power draw, Number of devices, Hours running per day, Electricity price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.