How to Choose the Right Battery Capacity (Ah) for Your Backup
A practical walk-through of sizing battery capacity in amp-hours: estimate your load, decide your backup hours, and match it to the right Ah rating.
Start with your load, not the battery
Capacity is measured in amp-hours (Ah), and the right number depends entirely on what you want to run and for how long. Before looking at any battery, add up the wattage of the appliances you actually need during an outage — a few lights, a couple of fans, a television and a router is a very different load from an office full of computers.
A simple sizing method
Estimate total load in watts, then divide by the battery voltage (usually 12V) to get the current draw in amps. Multiply that by the number of backup hours you want, then add roughly 25–30 percent headroom for battery efficiency, ageing and depth-of-discharge limits. The result points you to a practical Ah rating.
As a rough guide, a typical Indian home running essential lights and fans is well served by a 150Ah tubular battery, while heavier or longer backup needs move you toward 200Ah and above. UPS installations are sized differently, around the rack load and the runtime needed until a generator picks up.
Don't forget the inverter and the wiring
A large battery cannot deliver more than the inverter allows, so the inverter's VA rating and the battery capacity should be matched. Undersized cabling and loose terminals waste capacity as heat and shorten life. When you request a quote, share your load list and we will size the battery, inverter and configuration together.