Solar Panel Batteries

    Solar Panel Battery graphic

    Most rooftop solar arrays are connected to the grid, but there is another approach that drastically changes the equation: solar batteries.

    Solar panels work by collecting energy from the sun then generating a flow of electricity. From there, it is passed through the inverter and converted into a form of energy that powers your home. Solar has become one of the fastest-growing sources of energy in the United States, and has led to the development of solar gadgets and solar batteries.

    Without a solar battery, when your grid-connected solar panels produce more energy than you need, it is fed back into the grid. When your solar panels aren’t producing enough energy, you draw energy from the grid. But when you install a solar battery as part of your solar panel system, you are able to store excess solar electricity at your home instead of sending it back to the grid. Therefore, if your solar panels are producing more electricty than needed, that electricity is used to charge the battery. If your solar panels are not producing enough energy, you can draw from your stored energy. Check out a visual example of the process here. A solar battery will also provide backup for your home during electrical outages.

    Solar Battery Cost

    Solar batteries are currently on the expensive side. Solar batteries range from $5,000 to $7,000+, and from $400/kWh to $750/kWh. These prices reflect the battery itself and do not include the cost of installation or any additional equipment. When deciding to purchase a solar battery, you should think about both the gross price and price per relative capacity.

    It’s important to note that a solar battery may not be beneficial for every home. Saving money using a solar battery depends on how your utility company compensates you for energy fed back onto the grid. Here are some of the ways companies may compensate:

    • Full net metering: Most utilities companies use this type of system for their solar customers. How this works is you receive a credit on your electric bill for every kilowatt-hour of electricity your solar panels produce. You would NOT save money in this system if you were to use a solar battery.
    • Time-of-use rates: If your company has time-of-use rates or demand charges, or does not offer net metering, then solar batteries can help you save more when you go solar.

    Solar Power Battery Banks & Off-Grid Solar

    The alternative to the traditional solar panel battery system is to go completely off the grid with multiple battery bank storage. To get an idea if that would be feasible, let’s look at the numbers:

    In 2016, the average annual electricity consumption for a U.S. residential utility customer was 10,766 kWh, an average of 897 kWh per month. To be able to accommodate that level of usage, you would need 27,284 amp hours of battery storage – the equivalent of more than 600 standard car batteries.

    Going completely off the grid is risky. If your area has a bad weather spell or long periods without sunshine, you could risk not having power. Going completely off the grid requires a bit more than just a solar battery system. Products like Tesla’s Powerwall are designed to help you reduce the amount of electricity you are sending back to the grid, not live completely off the grid. You will need something much bigger and unfortunately, much more expensive.

    Solar Battery Innovation

    As you can tell, solar batteries have limitations and there is a struggle to go off the grid completely, which inspires continuous innovation in this space. Companies are spending a great deal of time and money to create batteries that would support grid-level solar use and revolutionize utilities. Here are a few examples of these innovative findings:

    Liquid Metal Battery

    • Created by MIT Professor Donald Sadoway. Professor Sadoway had the idea for a battery that is all liquid. Liquid metals for both electrodes and molten salt for the electrolytes.
    • In his 2012 TED talk, he said, “there is simply no battery technology capable of meeting the demanding performance requirements of the grid – namely uncommonly high power, long service lifetime and super-low cost. We need to think about the problem differently. We need to think big. We need to think cheap.” Watch his full TED talk here.
    • This could lead to a practical grid-scale storage.

    Heat Storage

    • A company called SolarReserve built a large solar plant in Nevada using molten salt that can store heat from the sun and generate electricity for up to 10 hours, even after sundown.
    • It is a 640-foot-tall tower surrounded by 10,347 mirrors. The heliostats, as they are technically called, are arranged in a circle that is 1.75 miles across.
    • “It is the first utility-sized project of this type in the world,” says SolarReserve CEO Kevin Smith.

    Compressed Air Energy

    • LightSail Energy sought out to revitalize compressed air energy storage with a more nimble and efficient technology as a cheaper and longer-lasting alternative to batteries.
    • Extra energy is used to run an air pump to fill a tank that compresses the air by 200 times.
    • When electricity is needed, the air is released to drive an electric generator.
    • The drawback to this invention is the heat it creates.
    • LightSail Energy went bankrupt before reaching commercialization.

    Ice Energy

    Get Started with Solar 

    If you already have a solar array on your home, the information above should help you determine if a solar battery is a money-saving option for you. If you are still deciding whether solar is right for you, virtually anyone using energy can save money, and reduce your carbon footprint, by going solar.

    Learn more residential solar