How to Size a Solar Battery Storage System for Your Site

Start with essential loads, not the biggest battery

List the appliances that must keep running during an outage: for example lights, refrigeration, communications, medical equipment, pumps or selected office loads. Record each appliance's power in watts and the hours it needs to operate. Their combined daily energy use, expressed in kilowatt-hours (kWh), is a better starting point for solar battery sizing than choosing a battery by price alone.

Separate essential circuits from optional loads. Air conditioners, motors and pumps can have high starting currents, so note both their running power and whether they may start at the same time. A qualified installer should verify surge requirements and wiring before a final design.

Estimate battery, inverter and solar capacity together

Battery capacity depends on daily energy, the required backup period, usable depth of discharge, conversion losses and any reserve you want. Inverter capacity must handle the maximum simultaneous load and appliance start-up surge. Solar array capacity must then be checked against the site's sun hours, seasonal conditions and the time available to recharge the battery.

These are connected design choices: a large battery cannot compensate for an undersized inverter or inadequate charging source. Treat online calculations as an initial planning estimate, not an engineering design or guaranteed runtime.

Prepare a useful quote request

Share your appliance list, city or project location, desired backup hours, existing grid or generator details, and whether installation is included. This helps suppliers compare a home solar battery system or commercial solar battery storage proposal on a like-for-like basis.