Electrical Load Calculator
Add your appliances to calculate total watts, daily and monthly kWh, electricity cost, and what size generator you need.
This free electrical load calculator helps you estimate your total power consumption and electricity cost. Add each appliance with its wattage, hours of daily use, and quantity to see your total load in watts and kilowatts, daily and monthly energy use in kWh, estimated cost at your electricity rate, and the minimum generator size you would need to power everything. It runs entirely in your browser with nothing to install.
Appliances
Generator size includes a 25% safety margin. Amps shown at 120V single phase. Actual costs depend on your utility rate and usage pattern.
How to Use the Electrical Load Calculator
Add each appliance using the preset dropdown or enter a custom wattage. Set the hours it runs per day and the quantity if you have more than one. The calculator totals your power draw in watts and kilowatts, works out your daily and monthly energy consumption in kilowatt-hours, and estimates your electricity cost at the rate you enter. It also shows the minimum generator size that could handle the total load.
Why Calculating Electrical Load Matters
Knowing your total electrical load helps you in several practical ways. If you are sizing a generator for backup power or a job site, the total wattage tells you the minimum capacity you need. If you are managing your electricity bill, seeing which appliances use the most energy helps you cut costs. And if you are planning a new circuit, panel upgrade, or solar installation, an accurate load calculation is the starting point for every decision.
How Electricity Is Measured
Watts measure how much power a device draws at any moment. Kilowatt-hours measure the total energy used over time — one kilowatt running for one hour equals one kWh. Your electricity bill is based on kWh, which is why this calculator converts your appliance list into both watts and kWh so you can see the cost impact directly.
Sizing a Generator
To size a generator, add up the wattage of everything you want to run at the same time, then add a safety margin of 20 to 25 percent for startup surges and future headroom. This calculator applies a 25 percent margin automatically and shows the result in kVA, which is the standard rating used for generators.
Frequently Asked Questions
How do I calculate my total electrical load?
Add the wattage of each appliance you plan to run at the same time. The total in watts is your electrical load. Divide by 1,000 to convert to kilowatts.
How do I calculate electricity cost from watts?
Multiply the wattage by the hours of use to get watt-hours, divide by 1,000 to get kWh, then multiply by your electricity rate per kWh. The calculator does this for you.
What size generator do I need for my house?
Add the wattage of everything you want to power, then add 25 percent for safety. The result in kVA is the minimum generator size. This calculator shows that figure automatically.
Why does the generator size include a safety margin?
Many appliances draw extra power when they start up, especially motors and compressors. A 25 percent margin covers these startup surges so the generator does not overload.