How does solar battery storage work?

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SunPower's SunVault solar battery storage

Making your home more energy-efficient is essential to many homeowners, and you may have come across the terms ‘solar battery storage’ or ‘energy storage.’ A solar backup system is becoming more popular if you want to maximize the amount of savings you make on your electricity bills from your solar panels. But how does solar battery storage work, and how can homeowners take advantage of this technology?

To ensure you’re up to speed on all the latest information, we’ve put together this short guide.

What is solar battery storage?

A solar battery storage system is a way of storing the energy produced from your solar panels. The energy stored can be used on many occasions, such as at night, on cloudy days, or during power outages.

Your battery storage system can store energy created by your solar panels during peak sunlight hours for later use. Using the energy from your battery storage solution is more efficient than drawing electricity from a power grid overburdened with users and more prone to power outages.

Solar and battery allow you to have an off-grid renewable energy system, enabling you to maximize the return on investment on your solar panels.

How does battery storage work?

Solar batteries function by capturing energy from sunlight through your home solar panels, converting it to direct current (DC) electricity. A solar inverter is a device that converts the DC power into alternating current (AC) electricity, which powers your home’s appliances.

The AC energy is directed to a switchboard where the electricity is sent to appliances, and if there is any excess, it is transported to your battery inverter, which converts the electricity into a storable form of energy.

At night or in essential times of need, your home will draw energy from the battery to power your home, also known as discharging. Then, when your backup power is exhausted, you will start to receive your energy from the grid until your solar panels start receiving sunlight.

Lead-acid vs. Lithium-ion batteries, what’s the difference?

What are lead-acid batteries?

Lead-acid battery (PbA) uses lead, sulfuric acid, water, and terminal metals (antimony and copper) to store electricity. They’re commonly found in cars, trucks, and boats. They have an output voltage of between 2V to 6V.

Lead-acid batteries are relatively inexpensive but are also heavy. As a result, they need a lot of maintenance and have a lifespan of approximately 5-10 years before they need replacing.

What are lithium-ion batteries?

Lithium-ion (LiON) batteries work similarly to lead-acid. However, they use lithium compounds as an electrolyte. This type of battery is made by many companies, including SunPower, Tesla, and Panasonic.

They’re lightweight, long-lasting (between 5 to 15 years), less toxic than lead batteries, and require less maintenance. Their output voltage is between 3V to 4.2V. Lithium-ion batteries are commonly used in mobile devices, laptops, and electric cars.

How do they compare?

Lithium-ion batteries are more expensive than lead-acid batteries but have a much higher energy density. For example, a lead-acid battery can produce 100Wh of electricity, but it would have to be more than 10kg in weight. To get the same amount of energy from a lithium-ion battery, you’d need only 1.5kg!

The typical life span of a Lithium-ion battery is 6,000 cycles at 90% discharge or 8000 cycles at 80% discharge. If you use your backup once a day, then it would last for 16 years. If you use your battery two times a day, it will last 8 years.

For home storage systems, we recommend you install a Lithium-ion battery because the lifespan outweighs the cost of installing and time maintaining a lead-acid battery.

Where does power go when the battery is full?

The purpose of a storage system is to store energy generated from your home’s solar panels during the day. Then, when your backup is full, any additional power generated will be pushed out onto the grid and sold to your utility for credits. This maximizes your return on investment because the excess energy that is sent to the grid offsets your electricity bill at times when you need it the most, such as at night and during peak power times.

How long can energy be stored in a battery?

Energy storage systems can store power for up to 3 days, depending on their size. That means you’re able to take advantage of as much solar energy as possible from your solar panels, even when clouds roll in, or the sun goes down.

How long do solar batteries last?

Energy storage systems last between 5-15 years, depending on how frequently they’re used and maintained. It would help if you considered this during your initial investment and the additional maintenance and replacement costs after the warranty period has expired.

Your solar battery can be directly affected by how you use it, what kind of storage system you choose, and where you live. For example, lead-acid batteries are vulnerable to freezing temperatures, while lithium-ion batteries aren’t as susceptible. Therefore, you should carefully consider your budget, the battery’s life expectancy, and how you will use your solar battery before investing in one.

Can I save money with the right energy storage?

Yes, if you want to save money and reduce your energy costs, installing solar storage would be wise. Depending on the size of your system, you’re able to store excess power from your solar panels during the day and use it at night or when electricity prices are high.

Using Solar Energy Storage during a power outage

With solar energy storage, you will be able to store enough energy to keep powering your home for up to three days after an outage occurs.

In this case, your solar panels will power your home and charge your battery during the day. And during times of low solar production, your storage system will power the appliances in your home for as long as possible. This cycle repeats itself.

Is solar-plus-storage worth the investment?

Solar-plus storage can offer you significant long-term savings. The battery system provides a backup power supply, so you won’t need to worry about power outages or being charged at a peak electricity rate. 

With the help of your solar battery, you may be able to gain off-grid status, helping you to achieve greater energy independence from utility companies.

You will still be able to save money and cut down on your energy costs by only using a solar panel system such as Equinox by SunPower. There are a few limitations to this. You won’t be able to store the excess solar power you generate during the day and use it at night or when utility rates are high. This means that you will have to draw from the grid, and you may end up paying more for electricity than you would if you had a battery backup. We’ll speak more on this later in the blog.

If you are considering battery storage for your current solar panel system, you should consider your home’s energy needs, your net metering agreement with your utility company, and compatibility with your current system.

The benefits of a battery system

  • Preserves the solar power your generate for when you need it the most.
  • Protects you from a power outage as you will not rely heavily on the grid for your electricity.
  • Stops you from overpaying for electricity during peak hours and saves you money on your electric bill. 
  • You can store excess energy that would have been sent to the grid.

What is a battery storage alternative?

Net metering can work in conjunction with solar and battery systems to provide homeowners with utility credits. Net metering cuts down on the amount you pay for electricity and helps encourage homeowners to invest in solar power.

What is net metering?

Solar net metering is when utility companies allow customers to sell any excess power your solar panels generate back to the grid. In return, you are compensated with credits that you can use to draw electricity from the grid.

There is a single electric meter that homeowners can see to get the ‘net’ of how much kilowatt-hours (kWh) they have delivered to the grid and how much they have received. A negative number will indicate that you have generated more energy than you have consumed, and your utility company will credit you.

What is Time-of-Use?

Time-of-Use (ToU) metering allows utility companies to measure and charge your home’s energy consumption based on when the energy is used. Time-of-Use prices vary by demand which is impacted by the season, time, day, and location.

The cheaper electricity costs are during off-peak hours, where demand is low and has less strain on the grid. Peak hours are usually early morning and late afternoon on weekdays. In some areas, peak hours may also occur on the weekends.

Summary: Is solar energy storage worth it?

Overall, a solar energy storage system can reduce your electricity bills, cut down on your energy costs, and help protect the environment. In addition, the battery backup gives you more control over how much you pay for electricity, which allows you to avoid paying high prices during peak hours.  

You can generally expect to pay between $4,000-$20,000 for a solar backup system which will help you save money while also helping you reduce your carbon footprint.

Do you want to know more about solar battery storage or want to save over 40% on your current electric bill? Then, reach out to our team of energy consultants for assistance with your home’s solar system. Call us on (609) 225-4101.


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Daisy Perez

Daisy Perez

Hi, I'm Daisy. I love solar energy! My job is to help people get the most out of their solar panels, and it's so amazing being able to do that every day.

I also enjoy taking trips to Blackwater Falls State Park in West Virginia for some serenity time – it's a great place for me to recharge my batteries and just relax.

But when I’m not doing those things, you can find me at home with my dogs or cooking up something yummy in the kitchen.

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About Solar Gleam

As a certified SunPower dealer, we’re here to help you learn more about solar, so you make an informed decision before making the switch. We’ve put together our best resources on how solar technology works, the role of solar storage, and the process of going solar for you to go through at your own pace.

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