How many batteries does it take to run a whole house?
The number of batteries required to power a whole house depends on three factors: daily energy consumption, battery capacity, and desired backup duration. For example, a household using 30 kWh daily with a 10 kWh battery (at 90% inverter efficiency and 80% depth of discharge) needs 5–7 batteries for 24-hour coverage. Lithium-ion batteries (e.g., 48V LiFePO4) are preferred due to higher efficiency and cycle life compared to lead-acid.
How is household battery capacity calculated?
Battery capacity calculations start with daily kWh usage. Multiply this by backup days, then adjust for inverter efficiency (85–95%) and depth of discharge (DoD). For lithium batteries, 80–90% DoD is safe versus 50% for lead-acid. Example: A 20 kWh/day home needing 2 days’ backup requires (20×2) ÷ (0.9×0.8) = 55.5 kWh.
First, audit your home’s energy use using smart meters or monthly utility bills. Heavy loads like HVAC (3–5 kWh/hour) and water heaters (4.5 kWh/use) dominate consumption. Pro Tip: Prioritize critical circuits (lights, fridge, medical devices) to reduce required battery capacity by 40–60%. For instance, a 10 kWh battery bank with 48V LiFePO4 cells (e.g., 4x 12V 200Ah) can sustain basics for 8–12 hours. But what if temperatures drop below freezing? Lithium batteries lose 20–30% capacity in sub-zero conditions, necessitating climate-controlled enclosures.
| Battery Type | DoD | Cycle Life |
|---|---|---|
| LiFePO4 | 80–90% | 3,500–6,000 |
| Lead-Acid | 50% | 500–1,200 |
What voltage system is optimal for whole-house setups?
48V systems balance efficiency and scalability. Higher voltage (e.g., 72V) reduces current, minimizing heat loss in wiring, but limits compatible solar inverters. Lower 24V systems require thicker cables for high-power appliances. Example: A 5kW inverter at 48V draws 104A versus 208A at 24V, allowing thinner 6 AWG wires instead of 3/0 AWG.
Most modern solar inverters and battery racks standardize on 48V. Beyond efficiency gains, 48V LiFePO4 batteries (like RackBattery’s 51.2V modules) seamlessly integrate with hybrid inverters. However, what if your existing system is 24V? Series-connecting two 24V batteries creates 48V, but ensure BMS compatibility. Pro Tip: Use UL-listed battery enclosures—code requirements in many regions prohibit DIY lithium packs for whole-house installations. Transitional setups combining solar and grid power often employ 48V battery banks with 5–10 kWh modules for flexible expansion.
RackBattery Expert Insight
FAQs
No—automotive lead-acid batteries lack cycle depth (20–30% DoD) and lifespan (50–100 cycles) for daily home use. Use deep-cycle batteries instead.
How many solar panels for a battery-only house?
Typically 20–30 panels (400W each) paired with 30–50 kWh storage, assuming 5 peak sun hours. Cloudy regions may need 2x capacity.