Daily energy load
Add up everything that needs to run off your solar setup. Foundation for sizing panels, batteries, and inverter.
Start here
Every other solar calc on this site needs your daily energy load as input. This one builds it up: list each piece of equipment, its wattage, and how many hours per day it actually runs. The total in watt-hours per day drives everything downstream.
Duty cycle for cycling gear
Heaters, fridges, and anything else that thermostats on and off don't actually run 24 hours a day. A 200W aquarium heater might only be on 25% of the time, which means it draws an effective 50W continuously. You can model that either way:
- "200W for 6 hours" (200 × 6 = 1200 Wh)
- "50W for 24 hours" (50 × 24 = 1200 Wh)
Use whichever feels easier. Same answer.
For pumps and lights that run on a fixed schedule, use the actual on-time. A pump that runs 15 minutes every hour is "Watts × 6 hours" (since 15/60 × 24 = 6).
Surge loads vs continuous
This calc only cares about energy (watt-hours over a day). Surge loads (a pump's startup spike, a compressor kicking on) get sized into the inverter rating, not the daily load. Keep the running wattage here.
Common gear wattages for reference
- Submersible pump (small): 15-40W
- Air pump: 3-8W
- Aquarium heater: 25-300W (cycles)
- LED grow light: 50-300W depending on coverage
- Standard LED light: 10-40W
- Small filter: 10-25W
- Exhaust fan (4 inch): 20-40W
- Phone / tablet charger: 5-20W (intermittent)
- Laptop: 30-65W
These are starting points. Check the actual label on your gear, especially for grow lights and heaters which vary widely.