Load Calculator
Turn a list of appliances into peak load and daily energy.
Free to use without an account. A free installer account adds saved work, A4 previews and branded PDF exports.
The load calculator turns a list of appliances into the four numbers every solar design starts from: running watts, motor-start surge, daily energy in kWh and night-time energy in kWh. Enter each appliance with its wattage, quantity and hours per day, and the totals update as you type.
How the Load Calculator works
List what actually runs
Add every appliance that can be on at the same time, including small loads such as decoders, routers and phone chargers. Missing loads are the most common cause of an undersized system.
Set realistic run hours
Use hours per day, not a guess at peak use. A refrigerator runs close to 24 hours with a duty cycle, while a pumping machine may run for two hours.
Read the four outputs
Running watts size the inverter, largest motor surge decides whether it can start, daily kWh sizes the array, and night kWh sizes the battery.
Worked example
A small home in Osogbo
Ten 10 W LED bulbs for 6 hours, a 150 W refrigerator for 24 hours, a 100 W television for 5 hours and a 750 W pump for 2 hours.
- 1,100 W running load
- 2,600 W motor-start surge
- 6.2 kWh per day
- 4.7 kWh used at night
Assumptions and limits
- Wattages are running watts from the appliance label, not manufacturer marketing figures.
- Surge is estimated at 3× for motors and compressors and 1.3× for other appliances.
- The calculator does not measure power. Confirm critical loads with a clamp meter before ordering equipment.
Frequently asked questions
How does the solar load calculator work?
Add each appliance, its wattage, quantity and hours used per day. The calculator totals the running load, includes the largest motor-start surge, and separates daily energy into day and night use.
Do I need an account to use the load calculator?
No. The load calculator is free and works without signing in. A free account is only needed to save work, preview A4 documents and export branded PDFs.
Can I use the result to size a solar system?
Yes. Send the result to the System Sizer to estimate inverter size, battery capacity, solar array size and panel count.
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Last updated 17 October 2026Maintained by Mishka Energy.
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