Energy Savings Calculator
Replacing an inefficient appliance or light bulb with a lower-wattage model saves energy every hour it runs, and those savings add up across a year. This calculator compares the old and new power draw, applies your real daily usage and your own electricity price, and shows how many kilowatt-hours and dollars you save per year. Because electricity rates and usage patterns differ from home to home, every figure that varies is a user-editable input, so the result reflects your situation rather than a generic national average.
Energy savings formula
old kWh/year = old watts * hours/day * 365 / 1,000
new kWh/year = new watts * hours/day * 365 / 1,000
energy saved = old kWh/year - new kWh/year
money saved = energy saved * price per kWh
old cost = old kWh/year * price; new cost = new kWh/year * price
One kilowatt-hour equals 1,000 watt-hours, so dividing watt-hours by 1,000 converts to the unit your utility bills in. The dollar figures use the electricity price you enter.
Energy saving facts
- An LED bulb typically draws 80 to 90 percent less power than the incandescent bulb it replaces for the same light output.
- Devices left on standby still draw power; switching them off fully removes that draw.
- Heating and cooling are usually the largest share of a U.S. household electricity bill, per the Energy Information Administration.
- Electricity prices vary widely by state, which is why this calculator uses your own rate.
- Simple payback in years equals the new device's purchase price divided by the annual dollar saving.
Energy savings: frequently asked questions
How do I calculate energy savings from a new appliance?
Find the power draw of the old device and the new device in watts. Multiply each by the hours used per day and by 365 days, then divide by 1,000 to get kilowatt-hours (kWh) per year. The difference is your annual energy saving. Multiply that by your electricity price per kWh for the dollar saving.
Where do I find my electricity price per kWh?
Your electricity rate is printed on your utility bill, usually labelled as cents per kilowatt-hour. It varies by state, provider, and plan, so this calculator takes it as an input rather than assuming a figure. The U.S. Energy Information Administration publishes average residential rates by state if you want a benchmark.
What is a kilowatt-hour?
A kilowatt-hour (kWh) is the energy used by a 1,000-watt device running for one hour. It is the standard billing unit for electricity. A 100-watt bulb left on for 10 hours uses 1 kWh. Utilities charge a price per kWh, so total energy in kWh times that price equals your cost.
Does this include the purchase cost of the new appliance?
No. This calculator shows only the ongoing energy and running-cost savings. To find a payback period, divide the appliance's purchase price by the annual dollar saving shown here. If the new device costs $100 and saves $40 a year, the simple payback is two and a half years.
Why use my own usage hours instead of a fixed estimate?
Energy use depends entirely on how long a device runs. A fridge runs continuously while a kettle runs minutes a day. Because real usage varies so widely, this calculator asks you for hours used per day so the result reflects your household rather than a generic assumption.
Official sources
- U.S. Energy Information Administration: Average price of electricity to ultimate customers.
- U.S. Department of Energy: Lighting choices to save you money.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.