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

6.5

SunPower SunVault

Like

• Large capacity batteries
• Unlimited cycle warranty
• Battery and solar equipment from a reputable solar company

Don't like

• Lower performance and efficiency
• Lacking modularity
• Fewer options for customer support

You're probably not shopping for just a solar battery; you're likely shopping for an entire solar panel system. 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 doesn't have the best performance or efficiency specs, but it does feature large amounts of energy storage capacity and 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."

What do I get with a SunPower SunVault battery?

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. 

System components

Most of 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: 

• Hub Plus
• Inverter
• Battery (ESS)

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 Plus , 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. 

Capacity and modularity 

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 maximum 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. 

Performance and efficiency 

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. 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.  

Warranty

The SunVault is backed by a great warranty. Unlike most batteries, the SunVault's warranty doesn't include a cycle or throughput clause. This means there's no limit to the number of times you can cycle (drain and recharge) your battery while it's covered under warranty.

Years covered: This is the length of time your warranty is valid for. The SunVault is covered under warranty for 10 years, which is the industry standard. 

Cycles covered: 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 is one of only a few batteries we've seen on the market that offers unlimited cycle coverage.

End-of-warranty capacity guarantee: Battery capacity tends to deteriorate over time. The capacity guarantee is the manufacturer's promise that your battery will be able to retain a certain amount of its original storage capacity by the time your warranty expires. SunPower guarantees your SunVault battery will retain at least 70% of its original energy storage capacity when your warranty period ends.

Customer support

Notice something weird with your battery system? Your installer should be the first person you reach out to. Since they are able to physically visit the site of the installation and are most familiar with your particular system, your installer will most likely be the most helpful in fixing any issues. 

But there might be times when you can't reach your installer. This is when you might reach out to the manufacturer for assistance. SunPower doesn't have many avenues for customer support. It does have a phone number, though, as well as some FAQs and helpful articles for troubleshooting. 

mySunPower app

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.

How much does the SunPower SunVault cost?

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. 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. 

Is the SunPower SunVault my best choice?

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. Are you only interested in backup power during outages, or are you also interested in offsetting your energy costs?  

The SunVault isn't the most efficient or modular solar battery, and it's a little pricey. It does offer larger storage capacity, decent power output, an excellent warranty and is backed by a solar company with a proven track record in the industry. While it's a fine battery option, don't limit yourself to just the SunVault. There's a wide variety of solar battery options available. 

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.

How we evaluated the best solar batteries

First let's be clear: Not every solar battery is right for every home. Solar is a very site-specific and personalized decision process, so it's a little tricky to pinpoint exactly which solar battery is the "best" battery for your home's energy needs without doing an on-site consultation. 

It should also be said that we didn't have any form of hands-on testing with any of the batteries we scored. This methodology also assumes you're purchasing a battery for the main purpose of using it for energy backup. If you mainly plan to use your battery for energy offset or to take part in a virtual power plant, there are likely better options than what we have featured in our reviews and rankings. We strongly encourage you to do your own research, as well as to speak with installers in your area. An installer will be able to get a better understanding of your home's energy use and what sort of system you might need. 

We used a few ways to evaluate and compare these batteries to find the stand-outs. Here's how we developed our list of top solar batteries.

First, we determined which categories would be used to evaluate each battery's performance, capacity and value. We also weighted each category. The weight of each category reflects the importance we felt was relevant to the average consumer: 

• Modularity: 20%
• Warranty: 20%
• Round-trip efficiency: 15%
• Power output: 15%
• Depth of discharge: 10%
• Price: 5%
• Price transparency: 5% 
• Customer support options: 10%

We looked at more than 15 of the most widely available batteries on the market and collected the data for each category to compare the numbers. Each category (for every battery) was given a rating (from 1 to 5) to evaluate which aspects of each battery were above average (among our list), just average or below average. 

Frequently asked questions