The SunPower SunVault storage system: The complete review

SunPower has always been known for its top-tier solar panels – now, they're expanding their influence in the energy storage space. In 2019, the company launched their first home solar battery: the Equinox Storage system. Now rebranded as the SunVault Storage system, this battery and software solution, when paired with a SunPower Equinox solar panel system, enables you to keep your lights on during power outages and manage your home's electricity use.

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A SunVault installation includes both a battery and a control system - SunPower calls this control unit the "Hub+." You also get access to SunPower's mobile monitoring app, where you can see the performance of your storage system and manage its settings. This is especially valuable if you pair a SunVault installation with solar panels. Specifically, and not surprisingly, SunPower recommends you pair SunVault with their solar solution, known as the SunPower Equinox.

The SunPower SunVault pairs well with solar panel systems, especially if your utility has reduced or removed net metering, introduced time-of-use rates, or instituted demand charges for residential electricity consumers. Installing a storage solution like the SunVault system with a solar energy system allows you to maintain a sustained power supply during both day and night, as long as you store enough power from your solar panels when the sun is shining.

As with many other home battery products, the SunPower SunVault is sized for day-to-day use at your home and is primarily designed to be paired with a solar panel system. When your solar panels produce more electricity than you can use in your home, you can store the excess electricity in the battery system instead of sending it back into the grid. Later, when your panels aren't producing enough electricity to meet your home's needs, you can use the stored energy in your battery instead of having to buy it from your utility company.

The SunVault system is a battery system from manufacturer SunPower. The SunVault system is a Lithium Ferrous Phosphate (LFP) battery, as opposed to the traditional Lithium-Ion NMC technology used in many batteries. This type of chemistry offers longer life, improved reliability, and increased safety. The physical battery is able to be wall-mounted, keeping it unobtrusive and out of the way in your home.

When evaluating the SunVault system, there are various important metrics and technical specifications to keep in mind. Among the most important are the size of the battery (power and capacity), its depth of discharge, and roundtrip efficiency.

Size

Two important metrics to keep in mind when comparing the SunVault system to other home storage options are power and usable capacity. Power (measured in kilowatts, or kW) determines the maximum amount of electricity that can be output at a single time, while usable capacity (measured in kilowatt-hours, or kWh) is a measure of the maximum amount of electricity stored in your battery on a full charge. The SunVault system comes in three sizes of usable capacity, all with the same power rating. You can get a SunVault system in capacities of 13 kWh or 26 kWh, both with a power rating of 6.8 kW. These batteries are known as the SunVault Storage 13 and the SunVault Storage 26, respectively – you'll see them referred to as such in most of SunPower's documentation.

Think of your battery like water running through a pipe: the usable energy capacity is the amount of water available to push through the pipe, while power is the size of the pipe itself. Larger pipes allow more water to flow through at once, which depletes the water faster. Similarly, a battery with a high power rating can deliver more electricity at one time but will burn through its stored energy faster too.

A battery's power determines the number of appliances you can run from the battery concurrently, while usable capacity determines how long those appliances can be run. Batteries with a higher power rating are capable of powering more, bigger appliances (i.e., your HVAC system) or many appliances at once, while batteries with a higher usable capacity can store more total energy and thus can run your appliances for longer periods of time without needing to recharge.

Basic functionality

The functionality of one solar battery next to another can vary; some batteries have excellent off-grid capabilities, while others offer software solutions specific to rate arbitrage. The SunVault system is designed to provide both of these services.

Performance metrics

Two key ways to evaluate the performance of a solar battery are its roundtrip efficiency and depth of discharge.

Roundtrip efficiency is a measure of electrical losses involved with charging and discharging a battery. The higher the efficiency percentage, the more efficiently the battery is able to convert incoming electricity into stored electricity and then back into usable electricity. Unfortunately, SunPower hasn't released the technical specifications for the SunVault quite yet, so we don't know an exact roundtrip efficiency rating for the product.

Depth of discharge (DoD) indicates the percentage of a battery's energy that has been discharged relative to the overall capacity of the battery. Because the useful life of a battery decreases each time you charge, discharge, and re-charge–or cycle–your battery, many battery manufacturers specify a maximum DoD level for optimal battery performance. In general, batteries with a higher depth of discharge are considered better-quality products. Unfortunately, SunPower hasn't released the technical specifications for the SunVault quite yet, so we don't know the exact depth of discharge rating for the product.

The SunVault Storage 13 system is backed by a 10-year, or 4,000 cycle/38 MWh throughput, product, and performance warranties that cover the equipment in the case of faulty parts or defects, as well as the actual performance of the battery. This means that SunPower guarantees your battery will still be able to store at least 70 percent of its initial out-of-box capacity by the end of 10 years or cycling your battery 4,000 times, or putting 38 MWh of energy through it.

For the SunVault Storage 26, keep the same number of cycles, but double the throughput numbers (as the battery is twice the capacity).

Importantly, SunPower's battery technology is similar to other rechargeable batteries, both large and small: as time goes on, the battery loses some of its ability to hold a charge. Think of how the battery life of a brand-new smartphone compares to one that is a few years old. As you continually charge and drain your phone's battery, it starts to lose some of its ability to hold a charge.

Warranty, capacity, and power are three of the most important metrics you should consider when comparing home battery options. If you want to compare individual battery models side-by-side, our Solar Batteries Buyer's Guide lets you select products and compare them based on efficiency, capacity, power, and more.

The cost of installing a battery isn't as straightforward as looking up the list price for an individual component–i.e., your battery. In fact, depending on your electrical setup, installation costs can vary widely. Unfortunately, SunPower has not released pricing yet for their SunVault battery product, but we're seeing prices around $15,000 being mentioned from individuals who have had their SunPower system installations completed.

If you want to install the SunVault system as part of a solar-plus-storage system, battery costs are just one piece of the equation. A five-kilowatt (kW) solar energy system costs anywhere from $9,000 to $15,000, depending on where you live and the type of equipment you choose.

That may sound like a lot of money, but installing a solar-plus-storage system can be a worthwhile investment. Whether or not the SunPower SunVault makes sense for you is determined by the way that your electric utility structures its rates, as well as your reasons for installing a solar battery.

In some cases, depending on where you live, you may have access to financial incentives that can reduce your home energy storage installation costs. For instance, if you live in California, you could get a cash rebate that covers most of your home battery costs through the Self-Generation Incentive Program (SGIP). Other states (such as Massachusetts) are in the early stages of evaluating battery storage performance incentives as well, and several states already provide cash rebates.

You can request a quote for a SunPower SunVault directly through SunPower's website or from local solar installers and/or installation companies that carry the SunVault system. Adding energy storage technology to your home is a complicated process that needs electrical expertise, certifications, and knowledge of the best practices required to install a solar-plus-storage system correctly.

A qualified EnergySage-approved company can give you the best recommendation about the SunVault system home battery system and other energy storage options available to homeowners today. If you are interested in receiving competing installation quotes for solar and energy storage options from local installers near you, simply join the EnergySage Marketplace today and indicate what products you're interested in your profile's preferences section.