SunPower SunVault Review: A Solid Solar Battery from a Top Solar Company

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It's not the most efficient battery on the market, but it comes from a trusted solar brand and packs a great warranty.

You're probably not shopping for just a solar battery. You're likely shopping for an entire solar panel system. And if you are, you might be considering SunPower, which is one of the top solar companies out there and offers the most efficient solar panels on the market. That means you might be getting SunPower's solar battery, the SunVault.

The SunVault isn't the most efficient choice on the market, but it does offer large capacity sizes and good performance. SunPower also offers a competitive, unlimited-cycle battery warranty. The SunVault was designed to integrate with SunPower solar panels and offers customers a more comprehensive system install approach. SunVault can be installed with third-party solar panels on an existing solar array as long as it's paired with a compatible inverter.

"With SunPower, you're going to a one-stop shop, so you get solar on your roof, you get the monitoring, and you get the storage," Nate Coleman, chief technology officer at SunPower, told CNET. "It's all coming from a single company, all backed by a single warranty."

Because solar batteries are part of a complex home energy system that depends on an individual home's needs, hands-on testing is incredibly difficult. This review is based on specs and information provided by SunPower online and an interview with Coleman and Ellen Kinney, vice president of digital products, marketing and public relations at SunPower, to get the most accurate and up-to-date information.

Here's what you should know about the SunPower SunVault.

SunVault's size options are on the larger side. Even its smallest size (13 kWh) is comparable to a Tesla Powerwall. A single SunVault battery can hold between 13 kWh to 19.5 kWh. If 19.5 kWh isn't enough, you can install an additional SunVault unit (also referred to as a double unit), to increase storage capacity up to 39 kWh.

Here's a quick breakdown of the SunVault's specs.

Most of the SunVault's components are consolidated into one or two boxes, meaning you won't need to have several boxes on the wall. Here's what you can expect to be installed with a SunPower SunVault:

The battery itself comes in the form of 6.5 kWh battery modules that are stored within a larger cabinet-like enclosure, referred to as the ESS. The battery enclosure also contains the inverter, which converts DC electricity generated by your solar panels into AC electricity that you can use to power your home. Inverters are essential. Without an inverter, you wouldn't be able to use solar to power your home. Next to your battery enclosure is the Hub+, which contains a few monitoring and control components, with the main one being the system's grid-interconnection device. This device functions as a transfer switch. It detects when the power grid is down and switches the system into backup mode.

The SunVault offers large capacity sizes but doesn't leave wiggle room for any smaller sizes in between. This makes capacity upgrades and finding a capacity size that's "just right" for your home a bit more difficult. The SunPower SunVault can be installed as either a single unit or a double unit. Each unit contains a specific amount of battery modules.

A singular battery module holds 6.5 kWh. A single SunVault unit contains either two or three 6.5 kWh battery modules for a capacity of 13 kWh or 19.5 kWh. If you need more energy storage, an additional SunVault unit (double unit) can be installed. A double SunVault unit contains either four or six battery modules of 6.5 kWh each for a capacity of 26 kWh or 39 kWh. You won't be able to install more than six battery modules, so if you hit 39 kWh, you're at max capacity.

When selecting battery size, consider your personal energy goals. Do you want whole-home backup or partial-home backup? Whole-home backup is exactly how it sounds -- your battery will be able to power your entire home during a grid outage. Partial-home backup is used to power "essential loads" during a grid outage. These essential loads are mainly just your large household appliances. The SunVault was designed with partial- and whole-home backup in mind. A single SunVault unit is best for partial-home backup, while a double unit is the better option if you're looking for whole-home backup.

The SunVault's performance and efficiency is a bit of a mixed bag. Let's start with what lags behind the competition: It's not the most efficient battery around. Most solar batteries we've seen have a round-trip efficiency of 90% or higher. The SunVault is rated at 86%. This means about 14% of the electricity generated by your solar panels will be lost on its way into battery storage.

The SunPower SunVault's depth of discharge is 92%, which is just a bit lower than the average we've seen on other deep-cycle batteries (95%). Depth of discharge is essentially a limit of how much energy you can drain (discharge) from your battery all at once without risking damage. So in this case, you'll be able to safely use 92% of the SunVault's stored energy. However, most manufacturers recommend you don't completely drain your battery before recharging it.

Now for the good: Performance-wise, the SunVault does about what you would expect for a battery of its size. A single SunVault unit has a continuous off-grid power output rating of 6.8 kW, and a double unit has a continuous off-grid power output rating of 13.6 kW. This means it shouldn't have too much trouble powering your appliances during a power outage.

The SunVault is backed by a great warranty. It's covered for 10 years, which is the industry standard. But it also comes with an unlimited-cycle warranty. Most manufacturers set a limit on how many times you can cycle (drain and recharge) your battery before the warranty ends. The SunVault's unlimited-cycle warranty means there's no limit to how often you use your battery. The SunVault and the Tesla Powerwall are the only solar batteries we've seen with unlimited cycle coverage. SunPower also guarantees your SunVault battery will retain at least 70% of its original energy storage capacity when your warranty period ends.

With most battery manufacturers we review, customer support seems to be hit or miss. SunPower's customer support is a hit, with high reviews from customers on SunPower's Better Business Bureau page. Many customers that left positive reviews report experiencing helpful customer service during app troubleshooting and throughout the solar installation process.

However, many recent customer reviews are negative. Customer complaints center around long wait times for installations and repairs, as well as having performance issues with their solar panel system after a few years.

With the SunPower SunVault, you'll also gain access to SunPower's energy monitoring app, mySunPower. With the app, you'll be able to monitor your battery's charge, designate energy to run specific loads, monitor solar production, and review time-series data on the performance of individual solar panels and the system as a whole. You'll also be alerted when your solar panels are producing energy at their best.

The mySunPower app offers several different power mode features as well. Cost Savings mode helps users avoid expensive time of use rates by limiting grid usage and using battery power instead.

"One of the unique features with cost saving mode is that the app will recognize when there's a high or low time of use rate and then adjust to what is most efficient for the customers so they can save the most money," said Kinney. "So by using this load offset, the battery charges and discharges in a manner that's most efficient for the customer, utilizing energy when it's not as expensive and storing energy when it's more expensive."

Self-supply mode prioritizes pushing all your excess generated electricity into the battery instead of sending it to the power grid. Reserve mode allows you to reserve a certain percentage of your battery's stored energy to be used exclusively during the event of an outage. The mySunPower app is highly rated on app stores, with the majority of users having a positive experience with the app's functionality.

The SunVault is a bit pricer than other solar batteries we've looked at. A single SunVault unit costs between $16,000 to $20,000, and a double SunVault unit starts at $26,000. These price estimates also include the cost of installation, according to SunPower. The company's battery capacity offerings are on the larger side, so the expense is to be somewhat expected. The larger your battery capacity, the more you'll likely pay. As a general rule of thumb, you can usually expect to pay between $1,000 to $2,000 per kilowatt-hour of energy storage. And the installation fees will generally cost around $3,000 or more.

Other factors affecting battery pricing are location, the installer and how many solar panels your home has. Speak with an installer in your area to get the most accurate price.

The SunVault might be your best battery option, or it might not be. It's hard to determine which battery is the "best" choice for your home without doing an on-site consultation and an energy audit. Your personal energy goals also play a role in which battery you should choose. Do you want partial or whole-home backup? Do you just want protection against short power outages, or are you looking to lessen your reliance on the power grid for the long-term?

SunVault isn't the most efficient or modular solar battery. And it's quite pricey. But it does offer larger storage capacity, decent power output, a great warranty and is backed by a solar company with a proven track record in the industry. While the SunVault is a decent battery option, don't limit yourself to just the SunVault. There's a wide variety of solar battery options available. And manufacturers continue to release new batteries every year. Installers will typically carry multiple battery options too. Contact solar installers you're interested in and see which batteries they carry.

Every solar battery is different and is not going to be the right fit for every home. Without an on-site inspection and energy audit, it's difficult to determine which solar battery is the "best" battery for a specific home. Due to the complex nature of solar panel systems, we're unable to do any kind of hands-on testing of any of the solar batteries we review. Instead, we focus on objective ways to evaluate and compare these batteries. Here's how we evaluate solar batteries.

First, we created categories to evaluate the battery's efficiency, performance, capacity and value. We then gave each category its own weight. Each category's weight reflects the importance we felt was relevant to the average consumer. These are the categories and their weights:

We looked at more than 15 of the most common batteries on the market and collected the data for each category to compare the data. Each battery was given a tier-style rating (from 1 to 5) for each category to see which metrics of each battery were above average (among those on our list), average or below average.

Yes, the SunPower SunVault battery is eligible for the federal solar tax credit. Any solar battery that can hold at least three kilowatt-hours (3 kWh) of energy and is installed in 2023 or later is eligible for the federal solar tax credit.

If you decide you want to go with SunPower for your solar needs, you can enter your ZIP code to find an authorized SunPower installer in your area. You'll then schedule a free solar consultation with your installer. If your location is serviced by SunPower's internal installation team, then SunPower will be performing your home's solar installation.