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What Do Batteries Do for Solar?

Everybody already knows what solar panels do. They turn sunlight into electricity. But what does it do to add batteries to the solar panel system?

The short answer is that the batteries store the electricity that the solar panels generate. So let’s talk about what energy storage can do for you.

If you are installing an off-grid solar system, storing the power is going to be important. Solar panels only generate electricity during daylight hours and in most cases you are going to want to use some of that energy at night. There are some exceptions like solar well pumps for irrigation or for filling a large holding tank. In these cases, it is okay for the pumps to stop working at night so the solar panels without batteries are going to be just fine. But if your off-grid system is running just about anything else, you will want to store the energy produced during the day so you can use it at night. 

Of course, most of you are installing grid-tied solar which makes the batteries less necessary, but they still might be useful. For one thing, even on the sunniest day, most grid-tied solar will not produce any power when the utility company has a power outage. The one exception is an SMA inverter which can be set up with one outlet so you have a small amount of power but only when the sun is shining and it is barely enough to run a refrigerator. If you want things in your house like the lights, fans, computers, microwave and dishwasher to work when power is off, you will need to add batteries to your solar. How much battery you put in will depend on what you want to run but it will typically be $10,000 – $20,000 to run your smaller appliances but if you want your whole house to work when the power is out you are going to need to spend some big bucks.

There are also some financial reasons to install the batteries but it depends on your electric rate and net metering rules. A classic example is the time-of-use (TOU) rates which are getting more popular in places like California. Being on a TOU rate means you will pay a high (peak) rate like $.30/kwh on weekdays between the hours of 4pm – 9pm and a low rate like $.15/kwh for the other hours of the day. Solar is going to generate the most power around noon when the electric rates are cheap so the batteries can store that power and you can use it at 8pm when it’s too dark to get much power from the solar panels but you don’t want to pay that peak rate to get power from the electric company. 

Another example of how batteries can help with your electric rates is if you have “demand charges”. Typically, demand charges are for commercial facilities but it is likely that electric companies could add demand charges to their residential rates. With demand charges, the electric company is going to charge you a dollar amount based on the largest amount of power drawn at one time during the month. Solar by itself might help with demand charges if you are pulling all that power during the day but as soon as you want a lot of power at night, the solar can’t help you unless you put in the batteries. With the batteries, you can set up the system to cover that surge of power any time you want it and you won’t have to pay the electric company that high demand charge. 

Net metering rules will also come into play on the battery decision. With true net metering, you give the electric company a kwh during the day and they give you one back at night. But, many of the net metering rules are changing so the electric company will still give you back that kwh at night but they will charge you $.02 – $.05 for doing it. If this is the case, you might be better off putting that kwh in your battery instead of feeding into the grid. Then you can use that kwh hour at night and nobody is going to charge you for it. 

So, that is what batteries do for solar. If you are installing your own solar, the battery systems are very easy to work with so if you can handle the DIY solar installation, you can do the battery yourself too. It is also fairly easy to add batteries to an existing system if you already have your solar and want to retrofit the battery system. Either way, call the experts at and they will help you decide what will work best for you. 

Author: Harold Tan

I believe clean, renewable energy is key to the evolution of society as a whole. Solar powers our planet, why not harness it to power humanity? Let's power our homes, our work, and our vehicles with solar energy. It begins with raising awareness and encouraging those around us to go green.

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