Understanding multi-unit property battery sizing
Why per-unit load estimates work well here
Rather than trying to total every individual appliance across every unit, estimating a reasonable critical loads figure per apartment, then multiplying by unit count, gives a workable planning number for most multi-unit properties. This calculator uses that approach, though actual per-unit load can vary based on tenant behavior and unit size, so treat the result as a starting estimate rather than a final design figure.
Shared system versus per-unit systems
Rental properties with a single owner and shared electrical infrastructure most commonly install one shared battery system managed centrally, while condos or properties with individually metered units sometimes install separate smaller systems per unit instead, giving each owner independent control. The right approach depends heavily on the property's ownership structure, existing electrical panel design, and whether tenants would be billed for backup power access, an arrangement discussed in the Department of Energy's shared and multi-unit solar resources. The modular battery stack tool covers how manufacturers handle combining many units together for larger shared systems.
Why inverter sizing gets more complex at this scale
A shared system serving multiple units needs an inverter, or multiple inverters, rated to handle the property's combined peak load, not just the average, a sizing principle explained in the Department of Energy's inverter basics guide. Multi-unit properties often benefit from working directly with a commercial or multi-family solar installer who has experience sizing systems at this scale, rather than treating it as a larger version of a single-family installation. The battery inverter pairing tool is a useful starting point for this conversation.
What to do with this number next
Once you have a property-wide battery count, the cost per kWh comparison tool shows what different battery brands would charge at this scale, and the quick financing comparison tool in our Financing category is worth reviewing given how much larger a multi-unit system's total cost typically runs. Consulting a licensed electrician familiar with multi-unit metering is worthwhile before finalizing the system design. If any units include EV charging, the multi-vehicle household solar EV sizing tool in our Solar + EV Integration category covers that added load.