A home solar battery gives your system solar backup power in case of a grid outage. It also provides a cushion of comfort in case you have uneven solar coverage on a given day or in a given season. Although most home solar systems do not realistically need the added expense of buying and maintaining a battery as a solar backup power source, how do you know if it is right for your particular situation? It primarily depends on your location and whether your home is off-grid or not.
Which Homeowners Need Solar Backup Power?
Most homeowners making the switch to solar power do not need to invest in a battery system. The majority of solar homeowners choose a grid-tied system. This kind of home solar system is linked to the larger power grid of the city or town. In case of a solar panel problem or a cloudy day, the home can pull some power from traditional electricity to keep the house running smoothly.
If your location means you will encounter uneven solar exposure, either because of the placement of your lot or because of the weather in your area, a solar battery system might make sense. Even if you are grid-tied you will want as few fluctuations in your power supply as possible so that you can minimize your dependence on the power company that runs your grid. If you only get a few hours of direct sunlight a day, a battery system can help you turn that sunny afternoon into 24 hours of reliable power without running up any expensive charges from the power company. A battery helps you get the most out of your panels when they are getting peak sun exposure so that you save the most money and cut the most carbon out of your footprint.
If you are a homeowner planning an off-grid system, then investing in a battery for some solar backup power immediately becomes much more important. Without the traditional electricity of your city or town offering a cushion for cloudy days or dark nights, your off-grid system is more vulnerable. A home solar battery can give your system its own safety net without relying on an outside power grid.
Home Solar Battery Capacity
If you talk to a home solar installation pro about batteries, they will probably mention the term “stackable.” The trend in home solar design is to create battery systems that “stack” multiple types of batteries and multiple sizes of batteries with different capacities. This gives you maximum protection and coverage.
There are two important metrics for a home solar battery. One is capacity and the other is power rating. The capacity is simply how much power the battery can store. The power rating is how much of that power it can deliver at a time. A battery with a low power rating can only let out a little bit of juice at a time.
If you are looking for a home solar battery that will power only a few key appliances during an outage, like your freezer and refrigerator, a low power rating but high capacity battery is a great failsafe. It will be able to give you a slow and steady stream of low power to keep those crucial units running for days or even a week. The reason you may want a “stackable” system is so that you can have a low power rating high capacity battery like this to be your workhorse while you add a flashier high power rating battery that could keep your whole house humming in comfort for a few hours or even a day. If you live in an area where the power grid is unstable or weather is unpredictable, a stackable battery system is probably worth your investment.
Home Solar Battery Costs
The only downside to the comfort and peace of mind that comes with a solar power backup battery system is the added cost. The U.S. Department of Energy quotes that a typical system costs between $380 and $895 per kWh. [1]U.S. Office of Energy Efficiency & Renewable Energy Many homes use about 30 kWh per day [2]U.S. Energy Information Administration which means a substantial price tag for a homeowner who is hoping to buy enough capacity to keep their system running full-tilt on battery power for much longer than a few hours at a time. New technologies are expected to make solar-tied batteries increasingly affordable for the consumer market in the future, but for now most solar installation professionals say that solar battery systems only make sense for off-grid homes or grid-tied homes in areas where brief power outages are particularly common.