Solar sizing calculator

How big a solar system do you need?

List what you want to power. AREIMS works out the energy you use in the rainy and the dry season, then the solar panels, batteries (gel or lithium), inverter, cables, breakers, earthing and lightning protection.

Free, no account needed. Your list stays on this device.

Where will it be installed?

The sunshine of the place decides how many panels you need. Rainy months have much less sun.

Country Region / county

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What will you power?

Add every appliance. Enter its power the way it is written on the label — watts, kW, horsepower, amps, VA or BTU — and how many hours a day it runs in each season.

Add an appliance

Your choices

The defaults suit most homes and small businesses. Change them if you know better.

Battery type

Lithium (LiFePO4)Uses 90 % of its capacity, lasts about 10 years, light, no maintenance. Costs more at the start. Gel (lead-acid)Cheaper to buy, but only 50 % of its capacity should be used, heavier, lasts about 3–4 years.

Battery model Solar panel System voltage Days of backup — rainy season Days of backup — dry season Mains voltage (AC)

Cable runs (metres, one way)

Panels → charge controller Controller → battery Battery → inverter Inverter → distribution board Roof / mounting height

Advanced settings

Design for Max PV input voltage of the controller / inverter Share used after sunset (%) Running at the same time (%) Reserve for future appliances (%) Inverter efficiency (%) Dust and dirt loss (%) Wiring loss (%) Heat loss per °C (%) Peak sun hours — rainy (leave empty = from data) Peak sun hours — dry (leave empty = from data) Currency for prices

Simulate it on your building

Find the building on the satellite map, place the panels on its roof and watch the system run through a day — sun, panels, battery and appliances. Wrong connections turn red with advice on how to fix them.

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Latitude Longitude

Drag the blue pin onto the roof, or tap the map where the panels will go.

Panels face (compass °) Tilt (°)

12:00

Speed Day

24-hour simulation

🔧 Change the wiring yourself (test connections)

Try other panel strings, controller, battery, inverter or cable sizes. The live system and the checks show at once what works and what is dangerous. The materials list above stays the recommended design.

🔎 Find an approved installer

This is an estimate for planning and comparing quotes. Before buying, an approved installer must check the site: shade, roof strength, earthing and local rules. Equipment values are typical, not a specific brand.