Battery Sizing Explained for Residential PV

Why battery sizing matters

An undersized battery fills by midday and wastes afternoon solar generation. An oversized battery never fully charges and degrades faster due to chronic partial-state-of-charge cycling. Getting the sizing right is the most important factor after module orientation.

Rule of thumb: 1 kWh per kWp

As a starting point, match battery capacity roughly 1:1 with installed PV peak power. A 10 kWp system pairs well with 9.6–12.8 kWh of usable storage. This ratio works for typical Central European households with daily consumption of 8–15 kWh.

Adjust for consumption patterns

• High daytime consumption (home office, EV charging from grid): the 1:1 ratio holds; morning PV charges the battery for evening use.
• High evening consumption, low daytime (commuters with EVs charging overnight): size up to 1.2–1.5× kWp to capture more afternoon generation.
• Flat daily profile with low peak (efficient homes under 8 kWh/day): 0.8× kWp is usually sufficient.

Consider backup requirements

If the customer wants whole-house backup, calculate the critical-load requirement separately: sum the wattage of essential circuits (fridge, lights, router, heating pump) and multiply by hours of backup needed. A 9.6 kWh battery at 90% DoD delivers ~8.6 kWh — roughly 12 hours for a 700 W critical load.

Sungrow SBR-HV sizing guide

The SBR-HV comes in 3.2 kWh module increments. Common configurations:

• SBR096 (9.6 kWh, 3 modules): suited to 8–10 kWp systems with moderate consumption
• SBR128 (12.8 kWh, 4 modules): suited to 10–14 kWp or high EV charging loads
• SBR192 (19.2 kWh, 6 modules): suited to large homes or commercial light-duty

Customers can always start with SBR096 and add modules on a follow-up visit — the stack expands without rewiring.