Home Solar Batteries

Choosing the capacity, chemistry and location of a home solar battery — from your household's real consumption, not a generic table.

Home lithium battery for a solar system. Conceptual image.

The challenge

The battery is the most expensive part of a home solar system and the part most often chosen wrongly. Undersize it and it empties earlier in the evening than expected and falls short in a long outage; oversize it and you have paid for capacity that never fully charges and never pays back. On top of that, the capacity on the label is not the usable capacity, and comparing two quotes without knowing depth of discharge and cycle life is comparing two meaningless numbers.

The SANA Energy solution

SANA Energy derives battery capacity from your household's actual consumption: the bill and the evening usage pattern show how many kilowatt-hours must be carried from daylight into the night, and the list of critical loads shows what has to stay on during an outage and for how long. The larger of the two is the usable capacity you need — and the nameplate figure follows from the battery's permitted depth of discharge, not the other way round.

Why this solution

Nameplate versus usable capacity

The figure on the battery is the total energy stored, not what you can draw without shortening its life. The permitted depth of discharge decides how much is genuinely available — and that difference is what separates two quotes showing the same capacity.

Why LFP, and where it does not matter

Lithium iron phosphate is thermally more stable and offers higher cycle life, which is decisive for a battery cycled every night. In an application used a few times a year, that advantage shows up far less.

Cycle life, not years of warranty

A storage battery's life is measured in charge cycles, not by the calendar. One cycled fully every night and one used weekly do not have the same calendar life — and that is what to look at when comparing two offers.

Expandable, if planned from the start

Modular batteries allow capacity to be added later, but that also depends on the inverter and the initial design. Without room planned in from the start, adding capacity means replacing equipment rather than adding a module.

Where it sits, and how warm

A lithium battery can be installed indoors, but ambient temperature affects both available capacity and how fast it ages. An unventilated store room in summer and an unshaded outdoor spot are both poor choices.

One purchase, two jobs

The same battery that carries daytime solar into the evening also holds the critical loads through an outage. Size for both uses from the start and there is no need to buy a separate backup system.