New: My equipment. Track products mentioned on the forum and build your own system. Go to Equipment > My equipment, search for a product and press "I own this", or press Watch on any product page to get an alert when a new thread tags it. Read more

Equipment

Loads planner

List what you want to run. The planner works out the battery, solar array and inverter size, then checks real products against it.

1. What you want to run

Appliance	Watts	How many	Hours a day	At once	Wh a day

Nothing added yet. Pick an appliance above; watts are typical figures, so change them to the label on yours.

Untick "At once" for things that never run together (the kettle and the microwave), so the inverter isn't sized for both.

2. Your site

Sun hours a day, worst monthPeak sun hours from a solar map such as NREL PVWatts. Use winter for off grid. Days of backupDays the battery should run without sun. Usable battery share%. About 90 for LiFePO4, 50 for lead-acid. System losses%. Heat, dirt, wiring and charging losses.

What you need

0kWh a day

0kWh of battery

0kW of panels

0kW inverter, continuous

How these are worked out

Battery: kWh a day x days of backup, divided by 0.9 for inverter losses and by the usable share.
Panels: kWh a day divided by sun hours, plus system losses.
Inverter: everything ticked "At once", plus 25% headroom.
Motor start: everything ticked "At once", with the largest motor counted at 3 times its running watts, since motors draw about that much for a moment as they start.

Check with real products

Typical appliance watts vary a lot between models; the label or a plug-in meter gives your real figure.

Equipment