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Battery backup buying guide: Here's everything you need to know

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Learn about whole-home battery backups to decide if they're right for you.
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During a power outage, having a backup power source can make a massive difference for your comfort and safety. In the past, that usually would have meant using a propane- or gasoline-powered generator. But today, there are much cleaner alternatives to generators, including backup battery systems.

Backup batteries run on electricity and can either work as a standalone device or as part of a home solar system. When the lights go out, your backup battery system will automatically switch on and serve as a source of electricity for several hours, a day or longer (depending on several factors, which we'll cover here). 

However, all of these benefits come at a cost. Installing a battery backup system can be a significant investment, so it's important to understand what's involved. For this guide, we've answered some of the most common questions about battery backup systems, including how they work, how they're made, how much they cost and where you can buy them.

Read more: Battery backup or generator: Which backup power source is right for you?

How battery backups work

As mentioned above, battery backups are powered by electricity. They can be charged in two ways: with electricity from your utility or from solar power as part of a solar panel system

If your battery backup is set up as a standalone power source and isn't connected to solar, you can expect it to provide power for several hours or a day, depending on how many appliances you're using. For more power, you can set up several batteries on the same system.

However, if your battery backup is part of a residential solar system, you can continue using your battery as long as your solar panels are generating power and sending it to your battery.

Benefits of battery backup systems

Whether you have solar panels or not, battery backups offer plenty of benefits. For starters, they help you gain energy independence, so you don't have to rely on the public power grid. This is especially critical if you live somewhere with frequent outages or blackouts (like California wildfire country).

On top of that, battery backups don't operate on fossil fuels and provide your home with clean energy. Unlike generators, they're nearly silent to run and don't emit carbon into the atmosphere.

Even if the power hasn't gone out, you can use your battery backup as a way to save money on your electric bills. For example, if you're on a time-of-use utility plan, you can draw on the energy from your battery during peak hours rather than paying sky-high electricity rates to your energy company.

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Different types of battery backups

There are several kinds of batteries used in battery backup systems, including lithium-ion, lead-acid and flow batteries. Here's a quick overview of each type.

Lithium-ion batteries

Lithium-ion batteries are the most common for home systems. Most of today's popular battery backup products are lithium-ion, including the Tesla Powerwall, Panasonic EverVolt and Generac PWRcell. They're lightweight and energy-efficient, making them perfect for home use.

Lead-acid batteries 

Lead-acid batteries have been used for hundreds of years and are the primary type of battery used in cars. They're cheaper than lithium-ion, but they aren't as efficient, which means they're best suited for small systems.

Flow batteries

Flow batteries (or redox flow batteries) are less common in home systems since they're mainly designed for commercial use. However, the technology appears promising, and it could become more widely used in residential battery backup systems in the near future.

Buying, setting up and maintaining a battery backup system

You can get battery backups from a range of businesses, including manufacturers, solar companies and battery retailers. The price will depend on which battery model you choose and how many you buy for your system, but most average-sized systems will run between $10,000 and $20,000 (excluding installation). If you're buying a battery backup as part of a solar panel system, however, you may qualify for a rebate or tax credit.

Once you've decided on a battery or batteries, make sure to have it professionally installed -- otherwise, you run the risk of electrocuting or injuring yourself. You can expect to pay a few thousand dollars for installation (which is separate from the cost of the battery).

After the initial setup, there's little maintenance required on a battery backup system. You won't need to replenish a fuel source (like you would with a generator), and there's no need for regular maintenance.

Lifespan and warranties

A few years after installation, you may notice that your battery backup system doesn't hold a charge as well as it used to. That's because, like other types of batteries, battery backups lose storage capacity over time. 

To account for this, battery backups include a warranty that expresses how efficient the battery should be by the end of the warranty period. The industry standard is 10 years and 70%, meaning that by the end of the 10-year warranty, the battery should still operate at 70% of its original performance. You'll find this warranty on many of today's most popular backup batteries, including the Tesla Powerwall and Generac PWRcell.

Is a battery backup right for you?

Battery backups make the most sense if you have a solar panel system or you plan on installing one with your battery. In these cases, your "solar-plus-storage system" will provide you with ongoing electricity when the power goes out. Without the panels, you're limited to however much energy is stored in your battery, and you'll have no way to generate more.

The bottom line

There's a lot that goes into picking a battery backup system. You need to consider many factors, including costs, battery types, installation logistics and the potential long-term return on your investment -- all of which can complicate the buying process. Hopefully, this guide can help you with that.

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