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.

For essential loads only, such as a refrigerator, lights, internet, and a well pump, a 10 to 15 kWh battery bank may cover an overnight outage. Powering most of a home, including HVAC, typically requires 20 to 30 kWh, while a fully off-grid setup may require 40 kWh or more. Use our solar calculator to estimate system size based on your appliances and energy usage.

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.