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Everything you need to know about home batteries

6 min read

home battery

Did you know a battery can help you use more of the solar power you produce, potentially saving you money on your electric bill? We’re not talking about a small flashlight battery, but an actual solar battery that stores your excess solar power to use in the evenings or in case of an outage.

Home Battery Benefits

There are several reasons why you might be interested in a home battery backup, and more than one way to do it. You can have a home battery connected to the utility for charging, but the most economical choice is to install a home battery that can be charged by clean solar power.

Pairing a rooftop solar system with home battery storage means you can charge the battery with your own panels instead of the power you buy from a utility - and this clean power can be replenished daily.

If you own or are considering a rooftop solar system, it’s a good time to consider a home battery backup as well. Home battery technologies have evolved significantly in recent years and they keep getting less expensive and more efficient.

With a rooftop solar system, power from your panels flows into the home to meet the household’s energy needs, and any excess solar energy is sent to the grid. During hours when panels don’t generate electricity (at night, for example), the home draws power from the grid. In states that support net metering, where you can send excess energy to the utility in exchange for a credit, this often balances out financially. But even if you don’t have net metering available where you live, a battery becomes especially helpful because it allows you to use your stored solar power in the evenings when the sun goes down. In states like Hawaii, for example, batteries make a lot of sense, because this is how you can make the most out of your solar energy system.

How Home Batteries Work

A home battery or storage system allows solar customers to store unused electricity for later use instead of routing it to the grid. In a power outage, your battery provides you with backup - because rooftop solar panels are tied to the grid, you’ll otherwise lose power during an area outage even if your panels are getting sunlight. Some batteries can also be charged by the grid.

The way your home battery is configured may impact which tax incentives you can claim, so you’ll want to be sure you understand all the particulars specific to your location before you have something installed.

The amount of battery backup power will depend on a variety of factors including the size and capacity of your battery (or batteries) as well as the energy demands of your home. Your battery installer should be able to explain the specifics to you and help you determine what is available and necessary for your home.

Best Solar Batteries

Now the real question...what are the options and which one should you choose? We’ve taken a look at some of the best solar storage batteries on the market and made a list that you can use to compare technologies, capacity, and durability.

Home Battery Technology

Lead-acid and lithium-ion batteries are the market standards for home energy storage. There are developing technologies like flow and zinc-air batteries, but the dropping price tag of lithium-ion batteries has secured them as the only major market players today for residential use.1

Lithium-ion is recommended for solar home batteries because of its long lifespan and high depth of discharge - which is tech talk for how much of the battery’s capacity can be used before it needs to be recharged. Basically, a high depth of discharge means you get more power out of each charge.2

Lead-acid batteries are typically cheaper upfront, but they have a shorter lifespan, require more maintenance, and have a lower depth of discharge. Lead-acid batteries are the type that power cars, boats, RVs, etc.

The current market leaders for U.S. residential batteries all use lithium-ion batteries: LG Chem’s RESU, Tesla’s Powerwall, and the sonnenBatterie. Each battery model will give you the advantage of backup power when you want it, but they’re not exactly the same.

Just like any other major home purchase, you’ll want to find the model that’s best for your needs. We’ll take a look at your options next.

Each of the batteries listed here is compatible with rooftop solar and offers an app to view your battery's charge and discharge. Some even allow you to control your battery use from a smartphone or tablet.

LG Chem RESU10H

This is a 9.8 kWh battery and you can stack two together for up to 19.6 kWh of storage depending on your home’s needs. LG Chem guarantees its battery storage capacity with a 10-year warranty,3 which is worth taking into account when you consider your potential return on investment. The RESU design also allows you to choose where in your home to install it.

The RESU is available in most solar markets - in fact, it’s quickly becoming the industry standard for U.S. residential installations, which can give homeowners additional peace of mind about the long-term stability of the product (and its warranty). Check with your solar installer to see if the RESU is an option for you and find out exactly what the price includes. Installation costs are usually extra and you may need to buy a dedicated battery inverter. (Vivint Solar offers the LG Chem RESU and it is compatible with Vivint Solar’s inverter, so no need for a separate one here on a new system.)

Tesla Powerwall

Powerwall offers 13.5 kWh of storage and can stack up to 10 batteries. Powerwall also offers a 10-year warranty but no guarantees on retained storage capacity or performance over time.4 The Powerwall is also available in most U.S. markets and is installed only by Tesla or a Tesla-certified installer. As with the RESU, the cost to install a Powerwall varies greatly but it does have a built-in inverter.

sonnenBatterie

Sonnen’s home battery is prevalent in Europe but not in the U.S. to date. Sonnens are available in capacities from 4 kWh to 16 kWh5 and also boasts a 10-year warranty and built-in inverter. Sonnens are usually the most expensive of the U.S. options and are only available through select installers.

Installing Your Home Battery

Installing a home solar battery is a lot more complex than changing the batteries in your smoke alarm and it’s best to have a professional do it. Some battery producers are partnered with rooftop solar installers to ensure flawless integration into your solar system. If you think a home battery is a good fit for your household, ask your solar provider if they offer home battery installation and which batteries they offer.

Because battery installation is just starting to gain momentum, solar companies may only offer them in some areas. If your area is not one of them yet, ask about a waiting list so you can be first in line when it’s offered in your city!

You can find out more about the RESU battery option and talk to an expert today.

Endnotes: 1. https://www.greentechmedia.com/articles/read/how-alternative-battery-makers-are-trying-to-compete-with-lithium-ion#gs.ogtBmjE 2. https://www.energysage.com/solar/solar-energy-storage/what-are-the-best-batteries-for-solar-panels/ 3. https://www.energysage.com/solar/solar-energy-storage/lg-chem-resu-battery/ 4. https://news.energysage.com/tesla-powerwall-vs-sonnen-eco-vs-lg-chem/ 5. https://sonnenbatterie.de/en-us/sonnenbatterie

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