Solar Batteries

Indoors, BigBattery is cheaper per kWh and has a 12-year warranty instead of 10. Outdoors, or for a permitted grid-tied build that needs UL9540A, EG4 is the one that is weather-rated and certified. Both are rated 8,000+ cycles and both run closed-loop with every inverter we sell, so neither choice locks in your inverter.

Essentials only like fridge, lights, internet and well pump. 10 to 15kWh covers an overnight outage. Most of a house including HVAC is 20 to 30kWh. Fully off-grid with no utility is 40kWh and up. Our solar calculator sizes it from your actual appliances.

ETHOS is modular in 5.12kWh steps. A complete system starts at 2 modules with the controller and rack, and scales to 80+kWh. The single 5.12kWh module is an expansion unit for a stack you already own.

It is now listed as the EG4 WallMount 280Ah All-Weather, which is the same 48V, 14.3kWh LiFePO4 battery with 200A continuous output, self-heating and a 10-year warranty, under its current name.

UL9540 certifies a complete energy storage system, which is a battery plus inverter, rather than the battery alone. Most utilities and inspectors require it for a permitted grid-tied install with backup. Off-grid systems generally do not. ETHOS and the EG4 314Ah Indoor cover UL9540 builds.

The batteries here are rated between 6,000 and 8,000+ cycles. Cycled once a day that is roughly 16 to 22 years before reaching the rated capacity floor, which is why these warranties run 10 to 12 years rather than the 2 to 3 typical of lead-acid.