This is where you store your surplus solar power so you’ll have energy to use after dark. There are a lot of batteries to choose from. As is the case so often in life, there’s a direct relationship between cost and quality.
RV/Marine/Golf Cart—These small batteries aren’t powerful enough to run an entire house, but if you have specific appliances you want off the grid, they’ll do the job.
The golf cart batteries won’t last as long and don’t have the capacity of bigger, more robust batteries, but they are some of the cheapest available on the market. This is where a lot of home solar experimenters begin.
Flooded Batteries—Lead acid batteries are produced specifically to be used with home solar systems. They’re called “flooded” because you add water to them over time.
They offer medium efficiency and medium affordability. However, using flooded batteries produces a gas during charging, so they can’t be stored or used indoors.
Gel Batteries—Gel batteries function much like flooded lead acid batteries, but they don’t produce any gasses. That means they’re safe for indoor use. However, they’re also notably more expensive.
Absorbed Glass Mat—These are considered some of the safest, most effective batteries for long term home solar use. They don’t give off any gasses, don’t have any risk of acid spillage, last longer, discharge slower, and maintain voltage better than golf cart, flooded, or gel batteries. The catch?
You get what you pay for—and you’ll pay a lot more for absorbed glass mat batteries. People who have used solar for years swear by them, but most of them also admit they started with a golf cart battery when they were first learning the ropes.