Off Grid Battery Sizing

TFTITFTI Registered Users Posts: 1
I'm planning to install solar panels/use a propane generator for a battery backed off-grid system. I've been searching online and have found conflicting information in regards to sizing my batteries. I'll require 6,000watts for 14hours from all the electronics I plan to run. I'd need at minimum a one day autonomy. Looking to use L16's or a fork lift batery for a 48v system. Any help would be much appreciated.

Can someone confirm that this battery sizing calculator is correct?


  • BB.BB. Super Moderators, Administrators Posts: 30,514 admin
    Welcome to the forum TFTI.

    First, just to clarify, is that 6,000 Watts * 14 hours per day = 84,000 WH per day = 84 kWH per day

    Or is that 6,000 WH (6 kWH) per day, over 14 hours (day time or night time)?

    If it is the first, then, at a minimum, you are looking at:
    • 84,000 WH per day * 1/0.85 AC inverter eff * 1/48 VDC * 1 day storage * 1/0.50 maximum discharge = 4,118 AH @ 48 VDC battery bank
    If this is a grow operation, you are pretty much stuck with power big (and power hungry) lights. If you have green houses, then you only need to add light in the morning/evening times (some have argued for nursery operations, that only need "some light" to extend the growing season, not "full sun" the whole time).

    If your needs are otherwise (pumping water, moving air, running a cell tower, etc.)--Then you probably should review your loads and take a serious stab at conservation. Many people can cut 1/2 (or even more) from their electrical needs if they work at conservation (new Energy Star Equipment, turn stuff off when not in use, insulation, etc.).

    In general, running a very large off grid solar power system (84 kWH per day is very large--That can power a very large home with full AC in Texas or Florida). Probably would need a proffesional installer if this is your first time and you don't have a lot of electrical/construction experience.

    If it is only 6 kWH per day, that is reasonable small system that works well for DIY folks.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.