What capacity do I need?
Start with your loads, power use, and required backup time.
Find My Battery Size
Battery Sizing Guides
Use battery sizing guides to choose the right kWh capacity for home backup, solar storage, off-grid power, and commercial battery systems. Final size depends on your loads, backup time, startup power, usable battery capacity, and inverter or PCS output.
Start With Your Question
How many kWh do I need for home backup?
Size storage for refrigerator, lights, WiFi, TV, home office, and essential loads.
Check Home Backup Size
What capacity do I need for solar storage?
Match storage capacity with daytime solar production and evening power use.
Check Solar Storage Size
What capacity do I need for off-grid power?
Size storage for night use, daily loads, and lower-solar periods.
Check Off-Grid Size
What capacity do I need for my business?
Size backup for POS, refrigeration, lighting, pumps, office equipment, and critical loads.
Check Business Backup Size
What capacity do I need for commercial storage?
Check load power, backup duration, pack kWh, and PCS output.
Check Commercial Storage SizeBattery Sizing Guides by Topic
What Capacity Do I Need for Home Backup?
Essential loads / Load power / Backup hours / 5kWh–20kWh options
Read Guide
What Capacity Do I Need for Solar Storage?
Solar production / Evening use / Backup loads / Storage capacity
Read Guide
What Capacity Do I Need for an Off-Grid System?
Daily loads / Night use / Solar recharge / Reserve capacity
Read Guide
What Capacity Do I Need for a Small Business?
POS / Freezer / Lighting / Router / Pump / Backup hours
Read Guide
What Capacity Do I Need for Commercial Backup?
Critical loads / Load power / Backup duration / Inverter or PCS output
Read Guide
How Do I Size a BESS by kW and kWh?
Peak load / Required power / Required energy / Backup duration / PCS size
Read GuideFeatured Battery Sizing Guides
10kWh vs 20kWh: Which Size Fits My Backup Loads?
Home loads / Longer backup / Solar storage
Read Guide
How to Size Essential Home Loads
Refrigerator / Lights / WiFi / TV / Security / Home office
Read Guide
How to Size Overnight Solar Storage
Daytime solar / Evening use / Night load / Storage capacity
Read Guide
How to Size Storage for a Small Business
POS / Freezer / Pump / Lighting / Router / Backup duration
Read Guide
How to Size Commercial Storage by Load and Backup Time
Load kW / Required hours / Pack kWh / PCS power
Read Guide
How to Size a BESS for Power and Backup Duration
kW / kWh / Peak load / Duration / PCS sizing
Read GuideRelated Tools & Products
Battery Size Calculator
Load power / Quantity / Backup hours. Get an estimated battery size in kWh.
Calculate Battery Size
Backup Runtime Calculator
Battery capacity / Load power. Estimate how long storage can support your selected loads.
Calculate Backup Runtime
FAQ
Do I need a full load list before choosing a battery size?
Yes. List the loads you want to keep running, their power, quantity, and required backup time.
Should I size for the whole house or only essential loads?
Start with essential loads unless you need whole-home backup.
Is 10kWh enough for home backup?
It can be enough for selected home loads, but the final size depends on load power and backup time.
What happens if the battery is too small?
Backup time will be shorter, and the system may not meet your required energy demand.
Is choosing a much larger battery a problem?
It can add cost and unused capacity. The battery must also match the inverter, charging source, installation space, and expansion plan.
Do pumps, HVAC, or motors change battery sizing?
Yes. Startup power must be checked in addition to normal running power.
Does solar charging change the battery size I need?
Yes. Solar charging can reduce stored energy needs during the day, depending on solar production and load timing.
Can I start with a smaller battery and expand later?
Yes, if the system, BMS, inverter, wiring, and installation design support expansion.
When should an engineer confirm the final battery size?
Engineer confirmation is recommended for larger home systems, three-phase loads, pumps, HVAC, commercial storage, off-grid systems, and BESS projects.