All About Solar
do you need them for rooftop solar?
When you install a solar battery as part of your home solar energy system, you can actually store the extra energy your solar panels produce at home instead of feeding it back into the electricity grid. With solar batteries, you maximize your ability to use the electricity generated by your solar panels on a day-to-day basis. During the times when you need more electricity than your solar panels are producing (later in the day or at nighttime), you can use the solar energy you have stored.
In most cases, you receive a credit on your utility bill for the electricity you send back to the grid. Later, when you are using more electricity than your solar panels have generated, you can use those credits instead of having to pay more to your utility.
Batteries can definitely provide a form of insurance against the risk of electricity prices going up and FiT going down. However, the benefits come at a cost. A typical payback period of an unsubsidized battery of that size is about 15 years. Most batteries have a 10-year warranty. Compare this with a solar energy installation without batteries. A regular non-battery solar power system has a typical payback of around 3-6 years, and will last about 25 years.
In conclusion, to make the decision if getting the batteries or not, you will need to think through the benefits and the costs to see if you prefer system with energy security or system that is cost-effective.
Reference: Energy Sage, Solar Quotes