1. Pick critical circuits
List only what must run during an outage. A fridge, sump pump, lights and internet usually total 1–2 kWh/day; adding heating or a well pump changes the design completely.
Backup is not whole-home storage by default. Pick the critical circuits first — sump pump, fridge, lights, internet, medical equipment — then size the battery and inverter.
A backup system needs a transfer switch or a dedicated critical-loads panel, a suitable inverter/charger, and a battery sized for the hours you actually need. Start with the loads you cannot live without, not the whole house.
Sizing rule: daily Wh first, then autonomy, then the model.
The arithmetic is simple; the mistakes come from using running watts instead of surge, or Ah without the voltage.
List only what must run during an outage. A fridge, sump pump, lights and internet usually total 1–2 kWh/day; adding heating or a well pump changes the design completely.
Motors and pumps can draw 2–3× running current at startup. Check the inverter’s surge rating and the battery’s continuous current; the 24V packs are rated 100A continuous.
Twelve hours covers most short outages; 24–48 hours needs a larger bank or a generator. Use the calculator, then add margin for cold and ageing.
Example: 1,500 Wh/day of critical loads, 1 day, 24V. Required ≈ 1,500 ÷ (0.8 × 0.85) = 2,206 Wh, or about 86Ah. One 24V 100Ah (2,560Wh) covers it; for 2 days, use one 24V 200Ah or two 24V 100Ah in parallel.
Assumes 80% depth of discharge and 85% inverter efficiency. Cold weather, ageing and higher inverter losses need extra margin.
Start with the smallest pack that covers the load, then check the bay and the inverter surge.
A native 25.6 V pack: half the current of a 12V pack at the same power, fewer inter-battery links.
Best for: Native 24V boats, trolling motors and small off-grid systems.
Bank limit: 1S4P
The largest pack we list today: 5.1 kWh in one 24V case, parallel up to 1S4P.
Best for: Home backup, larger 24V house banks, multi-day off-grid loads.
Bank limit: 1S4P
Three times the capacity of the 100 Ah pack in one box — fewer parallel connections and a 200 A BMS.
Best for: Full-time vans, larger 12V banks, long runtime without recharging.
Bank limit: 4S4P
Not sure? Use the sizing calculator, or send us the load list and we will check it.
Include the application, daily runtime, inverter size and destination market. We will reply with a model recommendation and the matching datasheet.