The answer to that question depends on if you have net metering. In Connecticut, both United Illuminating and Eversource offer net metering, or free storage of your power that you can then use at a later date when your solar system is not producing enough power. If your utility company does not offer net metering, then yes, you would need some way to store excess power produced for use when the sun isn’t shining. Batteries are not essential when you have net metering because the grid stores excess power produced, and gives it back free of charge when you need it.
But what about when the grid goes down?
If the electric grid goes off, the solar inverters shut down for safety, so you do not have power during an outage from the solar system on your roof. Many people install generators that work independently from solar and power the home or part of the home when the grid is off. The issue during an outage is that you still cannot use your solar power.
So what is the answer?
Batteries. Lead acid batteries, such as the ones found in cars, have been around for many years. So why are more people not installing them? The main reason is cost versus durability. A lead acid battery cannot be discharged below 50% of its capacity. This means you need to buy and install twice the amount of batteries you think you need in order to get the power storage capacity desired.
The second issue is the durability. Each time a lead acid battery is discharged, it loses a little more of its storage capacity over time, and eventually will not charge at all. This results in the need for twice the amount of space and batteries needed. And, on average they only last about 5 years or so.
Better technology. Lithium ion has changed the way all electronics are powered, from cell phones to electric cars. Lithium ion batteries are smaller, can be fully discharged, and last twice as long as lead acid batteries. Some manufacturers allow for the system to be designed with the battery and some allow for a complete retrofit no matter what type of solar installation. The big value is that the battery tricks the inverters into working even when the grid is out so you have access to the PV power already available to you. The challenge is sizing the battery to meet your usage needs while the grid is off. This is because even though you have access to your solar, it is limited by the size of the battery installed. Reviewing your power needs with a qualified consultant is important to ensure your system provides what you expect.
A federal tax credit of 30% is now available to help defer the upfront costs of battery systems as long as the battery is charged at least 75% of the time by your PV system. Once installed, there are no operating costs as compared to fossil fuel generators.
Batteries can typically be 30-50% more than that of a same size generator after incentives, so the costs are not yet equal, however if you do gain access to the power produced on your roof without the need of fossil fuels, the additional benefit of a battery backup system is that it recharges each day, indefinitely. Even if the grid never turns back on, or fossil fuels are no longer available, a battery backup system becomes a much better investment.
What is the right decision for your solar?
Options for homeowners are always available. Some homeowners may choose to wait and see if battery backup costs will become more affordable in the near future, while other homeowners want to be sure they can take advantage of the current incentives now before they run out.
Jeff Pipeling is the General Sales Manager at C-TEC Solar. Working one-on-one with thousands of homeowners in the solar industry, for more than 6 years, has given Jeff broad knowledge and technical understanding of the industry.