Buying Guide · 8 min read
How to Choose the Right Battery
A five-question framework field engineers use to specify a battery — brand-neutral, load-first, and honest about tradeoffs.
Start with the load, not the label
Every honest battery specification begins with one number: the actual load, in watts, that must run during an outage. Not the connected load — the essential load. Fridge, a few fans, lights, the router, one TV. Add them up. That figure decides everything downstream: capacity, chemistry, inverter size and cost.
Skipping this step is the single biggest reason homes end up with an inverter that hums for years while paying for capacity they never use.
The five questions we ask on every visit
1. What must stay on during a cut, and for how many hours? This gives capacity in watt-hours.
2. How often does power fail, and for how long? Frequent short cuts favour tubular; long or rare cuts favour lithium.
3. Is solar planned within three years? If yes, size the battery for solar autonomy from day one — retrofitting later is expensive.
4. Where will it live? Ventilation, temperature and space rule certain chemistries in or out.
5. Who will maintain it? A battery no one waters will die early, no matter the brand on the sticker.
Reading a warranty honestly
Warranties are two numbers, not one: the free-replacement window and the pro-rata tail. Only the first is worth much in practice — pro-rata claims after year three usually return so little value that customers rarely file them.
Compare batteries on free-replacement months first. A 24-month free-replacement warranty is almost always worth more than a 60-month pro-rata headline.
The specification that lasts
A well-specified battery is one you forget about. That happens when the capacity fits the load, the chemistry fits the usage pattern, and the install passes a written load test at commissioning.
We publish this framework so you can hold any installer — us included — to it. If a quote skips these questions, the number on the invoice is a guess.