Define what must stay on
List the essential loads during an outage, such as lighting, IT, refrigeration, water pumps and security, and for how many hours. That, not the whole building, sets the battery size.
Battery storage
Backup power that lasts as long as you planned.
Batteries fail expectations when they are sized on nameplate kWh, paired with the wrong inverter or never fully recharged. StimaPulse sizes storage from usable capacity, power limits and your real outage needs.
Size on usable energy
Usable capacity, round-trip efficiency and separate charge and discharge limits from the exact battery model are used in the calculation, not a generic rule of thumb.
Check the inverter can deliver it
Discharge power and the inverter rating limit how much load runs at once. Battery voltage and BMS communication protocol are checked against the selected inverter.
Make sure solar can refill it
Seasonal recharge screening confirms the PV array has enough surplus to recharge the bank, so storage is not oversized for the array.
How solar sizing worksPlan replacement honestly
Cycle and calendar life assumptions are explicit, and the estimated replacement year can be carried into the financial case instead of being ignored.
Combine grid, solar and generator
Compare battery-only backup with generator support and grid charging to find the lowest-cost way to meet your resilience target.
Frequently asked questions
How long will a battery power my building during an outage?
Roughly, the usable battery energy (kWh) divided by the load you keep running (kW). Usable energy is less than the nameplate rating because of depth-of-discharge limits and conversion losses, and the inverter's discharge power caps how much load can run at once. StimaPulse calculates backup hours from usable capacity, efficiency and discharge limits.
What is the difference between nameplate and usable battery capacity?
Nameplate capacity is the total energy the battery holds. Usable capacity is what the manufacturer allows you to use while protecting battery life. Sizing on nameplate alone is a common cause of systems that run out early.
Are lithium (LFP) batteries better than lead-acid?
Lithium iron phosphate (LFP) batteries generally allow deeper discharge, more cycles and higher efficiency than lead-acid, at a higher upfront price. The right choice depends on cycling, backup hours, temperature and budget, which StimaPulse lets you compare using the manufacturer's own ratings.
Can batteries recharge from solar after a cloudy day?
Only if the PV array has surplus energy beyond the daytime load. StimaPulse screens seasonal recharge so a battery bank is not sized larger than the solar array can refill.
Should I keep my generator if I add batteries?
Often yes, as backup for extended cloudy periods or very long outages. StimaPulse models generator-aware integration so the battery covers common outages and the generator covers rare long ones.
Get a plan for your site.
Bring a utility bill, load list, fleet schedule or supplier quote. We will turn it into a sized, costed and comparable plan.