Battery & storage
Enter your household loads and desired backup hours. Get a straightforward battery count for a standard single-family home.
How it works
Step 1
What matters is which circuits you back up, not your home's total square footage. The critical loads calculator and whole home backup tool both help build this list. Once you have this number, the oversizing for future battery calculator sizes the array around it.
Step 2
Most residential batteries range from 10 to 13.5 kWh per unit. Check your preferred brand's spec sheet for the exact figure.
Step 3
Each inverter has a maximum battery pairing limit. The battery inverter pairing tool checks this against your resulting count.
Battery count depends primarily on which loads you choose to back up and for how long, not the square footage of the home itself. A small home backing up its whole panel including HVAC can need more batteries than a large home backing up only critical loads. That said, larger homes do tend to have bigger HVAC systems and more circuits overall, which indirectly correlates with higher battery counts in whole home backup scenarios. The whole home backup tool and critical loads calculator both show how load selection, not size, drives this number.
Every inverter model has a maximum number of battery units it can pair with, commonly ranging from 3 to 10 depending on the brand and model, a limit set by the inverter's own charge and discharge current rating rather than the battery itself, as explained in the Department of Energy's inverter basics guide. A calculated battery count that exceeds your inverter's limit means either choosing a different inverter or accepting a smaller battery count and a correspondingly shorter backup duration. The battery inverter pairing tool checks your calculated count against typical inverter limits, and the hybrid inverter sizing calculator in our Inverters & Equipment category covers choosing the inverter itself.
Many installers recommend leaving some headroom in your inverter's rated capacity for likely future additions, such as an electric vehicle charger, a heat pump upgrade, or a pool pump, since retrofitting additional battery capacity later can involve a separate installer visit and higher marginal cost than including it upfront, a planning approach ENERGY STAR's electric-ready home guidance recommends for exactly these future loads. The battery expansion planning tool and oversizing for future battery calculator both address this planning approach directly.
Once you have a working battery count, the single vs multi battery cost tool shows how per-unit pricing changes at different battery counts, and the cost per kWh comparison tool compares what different brands charge for the total capacity you need. If you're financing this purchase, the loan payment calculator in our Financing category shows what different battery counts would cost monthly. The hybrid inverter sizing calculator checks whether your inverter can handle this result.
Questions
A single-family home backing up a 600 watt critical loads circuit for 24 hours needs about 17.4 kWh of nameplate capacity, or 2 batteries at 13.5 kWh each. Whole home backup including HVAC typically pushes this to 4 to 6 batteries instead.
Not directly. Battery count depends on which loads you choose to back up and for how long, not square footage itself, though larger homes often have more circuits and higher-draw equipment like bigger HVAC systems that indirectly push battery count higher.
Yes, each inverter model has a maximum number of battery units it can pair with, commonly 3 to 10 units depending on the brand and model. The battery inverter pairing tool checks this limit against your calculated battery count.
Many installers recommend leaving some inverter capacity headroom for likely future additions, such as an EV charger or a heat pump upgrade, since adding battery capacity later can be more expensive than including it in the initial installation. The battery expansion planning tool and oversizing for future battery calculator both cover this planning approach.