Choose a conversion within the same physical quantity. Watts and kilowatts describe power: how quickly energy is used or delivered. Watt-hours and kilowatt-hours describe energy accumulated over time. A percentage change separately compares an old value with a new value.
Formula
1 kW = 1,000 W; 1 kWh = 1,000 Wh. Divide by 1,000 to convert to the kilo-unit and multiply by 1,000 to convert back. Percentage change = (new value − old value) ÷ old value × 100.
Worked example
A 2,000 W appliance has a power of 2 kW. Running it for half an hour uses 1 kWh, equivalent to 1,000 Wh. Reducing annual use from 500 to 400 kWh produces a −20% change, meaning a 20% reduction.
What the result means
A conversion changes the unit, not the physical amount. A negative percentage means a decrease; a positive percentage means an increase. Use the electricity calculator when you also need operating time and costs.
Electricity price · India
Electricity duty, fuel or power purchase adjustments, fixed charges and subsidies depend on the applicable state and DISCOM rules. No national tax percentage or subsidy is assumed. Slab thresholds, sanctioned-load charges and time-of-day tariffs are not automatically modelled.
Assumptions and limits
Power cannot be converted directly to energy without a duration. Percentage change has no defined finite result when the old value is zero.
Questions answered
Is kW/h the same as kWh?
No. kWh is energy; kW/h describes a change in power over time.
Does a 20% reduction reverse a 20% increase?
No. The second percentage applies to a different starting value.
Data sources
- Bureau of Energy Efficiency: Star labelled appliances
- BEE: Appliance label and efficiency questions
- Delhi Electricity Regulatory Commission: Consumer bill guidance
- Ministry of New and Renewable Energy: Rooftop solar
Last reviewed: 2026-09-08