When adding solar to your home, one of the biggest decisions is whether to have battery back up or not and if so which type of battery will save you the most money while giving you the longest life cycle possible. The decision will be yours based on your own goals with your energy system and whether you want to spend the extra money to have battery backup.
The biggest benefit of having battery back up is not losing power when the grid is down. In Florida and other States along the East coast there is a chance of losing power due to a storm and having the battery back up can prevent power loss for any period and you can be fully independent from the grid for long periods of time or indefinitely. Typically, if you want to add battery backup this requires buying the battery bank and an extra inverter.
The size of the battery bank and inverter will be determined by how many electronics you wish to run when the grid is down. The less inexpensive way is to pick a battery bank size and inverter that can run the most essential electronics like refrigerator, microwave, oven, and lights. Your needs and your budget will likely determine if you want to run other less essential electronics.
AGM batteries and Lithium batteries offer the longest life cycles and are therefore cheaper in the long run than lead acid batteries, but they cost more than lead acid.
If you are thinking long term as it is typically the case when you invest in a solar system, it is worth giving Lithium batteries a serious consideration.
The benefits of Lithium batteries are undeniable since their much longer life makes them cheaper per charge cycle than any other battery.
Victron lithium batteries are extraordinarily high performance batteries. They need to be used in conjunction with the Victron BMS control system. Lithium-iron-phosphate (LiFePO4 or LFP) is the safest of the mainstream li-ion battery types.
A Victron Lithium battery does not need to be fully charged. Service life even slightly improves in case of partial charge instead of a full charge. This is a major advantage of lithium batteries compared to lead-acid.
Other advantages are the wide operating temperature range, excellent cycling performance, low internal resistance and high efficiency.