Generac PWRcell expert review: What makes it the most exciting new battery on the market?

Updated

The Generac PWRcell home battery and inverter.
The Generac PWRcell home battery and inverter.

The Generac PWRcell (pronounced “power cell”) is a whole-home solar battery backup system from a trusted American company long-known for its backup generators. It all started in 2019 when Generac bought Pika Energy, the original developer of the PWRcell, and Neurio, a manufacturer of home energy monitoring equipment. 

By combining the technology from the acquired companies with know-how from over 60 years of making generators, Generac began marketing PWRcell to compete with the likes of the Tesla Powerwall and LG Chem’s RESU home batteries. 

So how does the PWRcell stack up? Below is our complete expert review of the PWRcell ecosystem of products, with an analysis of specs and comparisons to other top batteries. But first, here are some important facts about PWRcell:

Key takeaways

  • Each battery cabinet can store between 9 and 18 kWh of energy using between three and six 3 kWh battery modules. Two battery cabinets can be combined for up to 36 kWh of storage.
  • PWRcell can deliver up to 12,000 watts of surge power to start heavy-duty appliances like well pumps and air conditioners.
  • When used with Generac’s Smart Management Modules, the PWRcell system can prioritize the startup of large appliances, allowing it to run more devices than any other solar battery system on the market.
  • The Generac PWRcell system can be installed alongside a new or existing solar system, and costs between $11,000 and $18,000, depending on the size of your system and where you live.
  • Additional 3 kWh battery modules can be purchased for around $2,000 and installed in the battery cabinet to add storage capacity as needs change.
  • The PWRcell can be paired with Generac’s backup generators to provide additional flexibility in power outages by charging the PWRcell battery if it gets low when the sun isn’t shining.

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    Find out if going solar with battery storage is worth it in your area

    How the Generac PWRcell works

    Like other home solar batteries, the Generac PWRcell is designed to provide backup power in the event of a grid outage and to save homeowners money by helping them avoid costly peak energy charges under Time of Use (TOU) energy rate plans. 

    The PWRcell stores energy generated by your solar panels and provides power to the home either when the sun doesn’t shine or when the grid is down. 

    Unlike other home solar batteries, Generac PWRcell is not just a battery box that hangs on your wall. Instead, it is an integrated system of components that can work together to make the energy storage system more effective and efficient. Generac makes every piece of equipment for a home solar system, except for the solar panels and racking.

    When part of a new solar installation, a PWRcell system includes the following main components:

    • SnapRS inline disconnect switches that go between each solar panel and allow for rapid shutdown in case firefighters need to work on the roof
    • PV Link substring power optimizers that take energy from the panels and send it to the battery and inverter
    • PWRcell battery modules to store solar energy, inside a specially-designed battery cabinet
    • A PWRcell solar islanding inverter that connects everything together and sends power to the electrical panel in your home

    Here’s how they all fit together:

    generac pwr cell diagramThe components of a full Generac PWRcell system. Image source: Generac

    The PWRcell battery and inverter can also be added to an existing solar system, and can receive up to 7.6 kW of solar power. In that situation, the system uses an Automatic Transfer Switch (ATS) connected between the main electrical panel and the PWRcell inverter. This switch allows the system to accept incoming power from the existing solar inverter and use it to power the home and charge the PWRcell battery, depending on the home’s needs and the battery’s state of charge.

    Connecting the PWRcell like this is called AC coupling, because the connection between the PWRcell system and the existing solar inverter happens after the power has been converted from Direct Current (DC) to Alternating Current (AC). By contrast, the full PWRcell system shown in the diagram above connects the Direct Current (DC) output of the solar panels to the battery, and converts that power to AC only when it is sent to the home’s main electrical panel.

    Here’s a diagram showing how the PWRcell works when AC coupled to an existing solar installation:

    A diagram showing how the PWRcell system can be AC coupled to an existing solar inverter. Image courtesy of Generac.

    Existing solar systems with greater than 7.6 kW output can also be AC coupled with the PWRcell. In this situation, the existing system’s output must be split, with up to 7.6 kW available for charging the PWRcell battery and the rest going to power the home. In a power outage, only the 7.6 kW connected to PWRcell system would be available for use.

    Now let’s look at each of the components that come with the PWRcell system.

    SnapRS switches and PV Link optimizers 

    These are fairly straightforward pieces of hardware that have an important job in the PWRcell system. 

    The SnapRS switches connect between each solar module in an array and will shut down the output of that module within 10 seconds from whenever the inverter is turned off. Rapid shutdown is a fire code requirement of solar systems, and these switches are how Generac accomplishes this task.

    The PV Link boxes are substring power optimizers. They attach between a short string of solar panels (up to 2500 W) and the inverter, and ensure that the DC power delivered by the panels gets sent to the inverter as soon as panel output reaches 60 volts. The PV Link was initially developed by Pika Energy to integrate with the PWRcell battery. 

    Because they optimize the power output of a string of panels, the PV Links are somewhat less efficient than microinverters and DC power optimizers, which are attached under each solar panel in an array. The advantage of the PV Link is having fewer points of failure, at the expense of a little less energy output over time. For people who want the extra juice, Generac has announced its own microinverters, which will be available later in 2022 (more on these below). 

    The PWRcell battery cabinet 

    The PWRcell battery cabinet can hold up to 6 modules, each of which can store 3 kWh of usable electricity. The cabinet can be set up with 3, 4, 5, or 6 modules, allowing 9 - 18 kWh of storage. Here’s how that looks:

    Generac’s modular battery cabinet designGenerac’s modular battery cabinet design allows for future capacity expansion. Image source: Generac

    If installed alongside the PV Link optimizers and SnapRS rapid shutdown devices, the PWRcell’s battery is charged using DC power sent directly from the solar panels. This makes the battery very efficient compared to batteries like the Tesla Powerwall and sonnenCore, which charge using energy that gets converted from DC to AC and back again, causing some loss of energy in the process.

    When the PWRcell was first launched, this DC-coupled setup was the only supported way to install it. On August 9th, 2022, Generac launched its Automatic Transfer Switch (ATS), allowing the PWRcell to be installed as an AC-coupled battery. In this setup, the PWRcell can easily accept AC power from an existing solar inverter. It can also be attached to one of Generac’s fossil fuel generators for additional backup flexibility. The AC coupled setup requires a full M6 battery cabinet, with 18 kWh of storage.

    Learn more: Is a DC or AC battery right for your home?

    The PWRcell inverter 

    The Generac PWRcell inverter was designed to operate a home in grid-connected or “islanding” mode in case the grid is down. It can be set by the homeowner to one of several modes, including backup power, self-supply, time-of-use, and zero-export. 

    The inverter comes in two models: 

    • X7602, which can provide up to 7,600 W of single-phase AC power when connected to the grid
    • X11402, which can provide up to 11,400 W of 3-phase AC power when connected to the grid

    Most homeowners will end up with the X7602, while commercial businesses are the target customer for the X11402.

    Both inverters can accept up to 30 A @ 420 VDC from solar panels, and both output 9,000 W continuously in islanding mode when connected to one 18-kWh PWRcell battery. Both inverters can deliver up to 12,000 W to start a motor. That’s a very impressive number, as it means a PWRcell inverter can start a well pump, sump pump, or a 3-ton HVAC unit.

    Optional components in the PWRcell system 

    In addition to the required components, Generac also makes some optional pieces of equipment to provide extra flexibility. They are:

    • Automatic transfer switch (ATS)
    • Smart Management Modules (SMMs)
    • Sure-Start HVAC soft start box

    This is where the PWRcell system really eclipses other home energy storage solutions. Generac brought these components from their home generator business to complement the PWRcell battery. The ATS and SMMs automatically shut certain appliances down, based on priority, to start up other appliances that require high surge power. 

    Using these components, homeowners can run nearly their entire home on a single backup battery in the event of a grid outage—something many other companies’ batteries can’t provide. Altogether, this makes the Generac PWRcell one of the most exciting home batteries on the market

    Automated Transfer Switches 

    These specialized pieces of equipment control the flow of power inside the home. As the name implies, they automatically send power to appliances, the PWRcell battery, or the grid, depending on the needs of the home at any given time. In addition, the Generac ATS isolates the solar and battery during a power outage, allowing them to continue to operate independently from the grid in “islanding mode.” Finally, using a Generac ATS can allow a single PWRcell inverter to manage up to four individual HVAC units, turning them on and off so they don’t overload the inverter’s capacity by starting all at once. An ATS is required for AC coupling.

    Smart Management Modules 

    Generac SMMs are small boxes that contain hardware to turn a given circuit off and on, based on how much of a priority it is to keep powered. They are installed in-line, which means they need no external power or communication—the circuits are turned on or off via a powerline signal from the PWRcell inverter. 

    Basically, when the appliance wants to start, the SMM tells the inverter to check whether it can. If a higher-priority appliance is running, the SMM will not allow its appliance to start up. When the higher-priority device is no longer running, the SMM allows the lower-priority device to start. This way, the home’s appliances can all run off the same inverter and not overload the circuit by all drawing power at once.

    PWRmanger

    Generac’s most recent innovation is the PWRmanager, which it calls an “advanced load management device.” This small box can take the place of several SMMs, providing a centralized automatic load management solution. Essentially, the PWRmanager’s job is to selectively shut off certain loads to prevent too much current from being drawn at once. This allows the PWRcell to provide whole home backup while not overloading the inverter. Users can also turn individual circuits on and off by using Generac's PWRview app.

    Sure-Start HVAC soft start box 

    This piece of equipment is used to reduce the start-up current that an air conditioner compressor needs. It further reduces the peak power consumption needed and allows the PWRcell system to keep running essential equipment as an air conditioner starts.

    How Generac’s optional components work 

    Here’s a look at how SMMs and a Sure-Start box work within the PWRcell system:

    pwrcell smm diagramImage source: Generac

    The image above shows how the PWRcell can power three of the most important appliances in the home as it operates in a grid-down situation. Here’s what’s happening, from bottom to top right in the image:

    • The sump pump is wired without an SMM so it will always receive power when it needs it
    • The well pump is set to Priority 1 using an SMM to turn it on whenever it needs to run to supply water to the home
    • The 3-ton A/C is set to Priority 2 and allowed to run when the well pump is not running. A Sure-Start box is attached to keep the current it draws from overwhelming the inverter
    • The 5-ton A/C is set to “lockout” using an SMM, which means it will not turn on when the grid is down, because it would draw more power than the PWRcell inverter can provide

    Generac’s PWRview monitoring app 

    Another optional addition to your PWRcell system is Generac’s PWRview monitoring app. 

    It’s a one-stop-shop for information about energy generation and usage in your house. The app contains data on solar generation, battery charge, grid usage, and more - and can even give you an estimate of your next utility bill based on that data it’s collected if you enter your rate plan.

    It certainly sounds like a good app to have, and its functionality is similar to other solar monitoring solutions from equipment manufacturers and solar installers. Unfortunately, reviews of Generac’s Android and iOS apps are not positive. Users complain about glitches, missing data, bad customer service, and more. This seems to be one area where Generac has stumbled, in regards to its PWRcell system.

    If you’re curious about how the app works, check out the below video about its features.

    Cost and availability

    Generac’s PWRcell components are sold through a nationwide network of licensed dealers, so pricing can vary, depending on the area where you live. That said, we do have some pricing information.

    Generac has said that a minimum-size 9 kWh PWRcell system will cost $12,435, plus installation costs, which we estimate will be around $2,000 more than a solar installation without a PWRcell.

    Each battery module can be purchased separately for about $2,000, so the cost of a full-sized 18 kWh PWRcell system ranges from about $20,000 to $22,000 installed, depending on offers from dealers in your area.

    The good news is that the PWRcell is eligible for solar storage incentives in certain areas. Not only that, but when you install a solar system, you can claim the federal clean energy tax credit. These incentives (as well as other applicable incentives and rebates you may qualify for) can reduce the cost of a solar-plus-battery storage system substantially.

    Try our solar cost calculator to see what an installation would cost you

    PWRcell warranty information

    Generac is a solid, reputable company that stands by its products. You can count on it to be around for decades to come. While that’s a good basis for trusting a warranty, the numbers need to be right. Let’s see how well they fare when it comes to offering their customers protection against product failures.

    The good news is, the Generac PWRcell warranty covers parts, labor, and limited travel (100 miles/3 hrs maximum, per occurrence) for all components of the PWRcell system. The length of coverage depends on the product type and Generac promises the products will be free from defects in material and workmanship during their coverage period. 

    Here’s a look at how long each component is covered:

    Generac PWRcell warranty information
    Component Warranty coverage
    PWRcell battery cabinet 10 years
    PWRcell battery modules 10 years or 7.56 MWh of energy throughput per module; whichever comes first
    PWRcell inverter 10 years
    PV link 25 years
    SnapRS 25 years

    Importantly, the pieces that are going to stay up on your roof for 25 years (PV Link and SnapRS) are warrantied for 25 years. The PWRcell inverter and battery come with 10-year warranties, which is fairly standard in the industry for these components. 

    Additionally, the throughput warranty for the battery modules is fairly standard. To put it in perspective, if you drained each battery module 100% of its usable power (3 kWh) every day, you’d get to 7.56 MWh in about 6.9 years. The vast majority of people will choose to retain some battery capacity for emergencies, and therefore, will use less. To get to the full 10 years, don’t go over an average of 69% drain per day.

    Unfortunately, the PWRcell battery module warranty doesn’t say anything about how much capacity the modules will retain over those 10 years; only that they will be free of defects in materials and workmanship. If you think the batteries have lost more capacity than they should, it’s up to you to convince Generac of that, and up to them to agree with you.

    This isn’t normal. Many other batteries on the market, including the Tesla Powerwall and its main competitors, guarantee between 60% and 70% of the original capacity at the end of their warranty periods. This is an oversight for Generac. We’ll update this article if that changes.

    Can you go off-grid with Generac PWRcell?

    Going off-grid with solar is not for the faint of heart. In general, you need to oversize your solar system and battery capacity to generate and store enough electricity to get through 2 or 3 days with little to no sun, something you very well may experience - especially in the wintertime. An alternative to an oversized solar system is a fossil fuel backup generator.

    The PWRcell system can interface with two kinds of Generac backup generators: the Guardian HSB and the new PWRgenerator. Guardian series generators start at 10 kW of power output and top out at 26 kW, while the PWRgenerator puts out 9 kW. Generac says the Guardian series is better for those who want whole home backup with minimal load management and the ability to start large loads of 50 amps or greater, while the PWRgenerator is better for those who want the quietest possible generator that uses as little fuel as possible.

    The Generac Guardian 26 kW and PWRgenerator 9 kW side by side. Images from Generac: Guardian and PWRgenerator

    These generators are the backup to your backup. The PWRcell system will detect whenever the battery discharges to 30%, then turn on the PWRgenerator to recharge the battery to full. Generac says the PWRgenerator can charge a 12-kW battery from 30% to full in about an hour, and the Guardian series generators would do it even quicker. Depending on the size and model of the generator, these options can cost between about $5,500 and $9,500.

    Although a generator and the PWRcell system should keep your home running during extended power outages as long as you have fuel and sun, Generac has shied away from saying the system can work in a true off-grid setting. That kind of promise has to come with robust provisions for redundancy and the proven ability to perform a black start (aka, start up the whole system with no outside power source), and Generac hasn’t done the testing and extra work to prove that.

    A diagram of the full Generac PWRcell system. Image: Generac

    More information on how the PWRgenerator works is available in this Generac datasheet (PDF), and information on Guardian series models is here.

    How PWRcell compares to other top home batteries

    We’ve made allusions above to how PWRcell compares to Tesla’s Powerwall, but let’s make the facts more explicit here, and add a comparison to LG Chem RESU Prime batteries, which are another of the top home energy storage solutions.

    PWRcell differs from the Powerwall and RESU batteries in a couple of key areas: 

    • PWRcell is a DC- or AC-coupled modular battery system available in multiple capacity sizes of between 9 kWh and 18 kWh; two can be connected together for a total of 36 kWh of storage.
    • Tesla Powerwall is a single AC-coupled battery box that comes in one size: 13.5 kWh. Multiple Powerwall batteries can be installed together.
    • LG Chem RESU Prime batteries are DC-coupled batteries that come in 9.6 and 16 kWh sizes. They must be paired with an inverter that is built for paired storage.

    Here’s a comparison of key data points of these three market-leading home energy storage solutions:

    Generac PWRcell specs vs. Tesla Powerwall and LG Chem RESU Prime
      Generac PWRcell Tesla Powerwall+ LG Chem RESU Prime
    Power connection DC or AC AC DC
    Battery chemistry Li-NMC Li-NMC Li-NMC
    Capacity 9 - 18 kWh 13.5 kWh 9.6 - 16 kWh
    Max. continuous output 4.5 - 9 kW 5.8 - 9.6 kW* 5 - 7 kW
    Peak power output 6 - 12 kW 10 - 22 kW* 7 - 11 kW
    Round-trip efficiency 96.50%/90%** 90% >90%
    Warranty 10 years 10 years 10 years
    Throughput warranty (MWh per kWh of storage) 2.52 2.8 3.35
    End-of-warranty capacity N/A 70% 70%
    Average installed cost $11,500 - $17,000 $10,500 $9,000 - $12,000
    Energy monitoring app Yes Yes 3rd party
    EV charging in-app No Yes No
    Load prioritization Yes No No
    Generator integration
    Yes No Depends on inverter

    *Tesla Powerwall+ output depends on whether the grid is up or down, and also increases when paired with a solar installation of at least 4 kW under full sun. A solar installation of more than 12 kW is necessary for peak power output of 22 kW.

    **96.5% round-trip efficiency when DC coupled, 90% when AC coupled.

    One thing we can’t capture with a single data point is availability

    As of August 2022, both the Generac PWRcell and LG RESU Prime batteries are available from installers all around the country, while the Tesla Powerwall has at least a 3-6 month waiting period after ordering. All of the batteries listed above can be installed by many different solar installers, so contact companies near you to get quotes for solar and home energy storage.

    Concerns about past performance

    There have been many reports of performance issues from users of Generac’s original version of the PWRcell system. In particular, the original versions of the SnapRS rapid shutdown devices (801 and 801A) seem to have had a flaw that could cause them to overheat and undergo thermal failure, leading to a lawsuit from at least one company, Power Home Solar. Generac has since developed a new version of the rapid shutdown device, the SnapRS802, to replace the older versions.

    Bottom line: Is the Generac PWRcell system right for you?

    As we outlined above, the Generac PWRcell is an exciting entry into the home energy storage market and has some unique features that set it apart from the competition. If you’re looking for home battery backup for emergencies that can also help you avoid high peak energy costs under a Time of Use billing plan, the PWRcell is an excellent choice.

    If you’re looking for a solution that can take you off the grid, the PWRcell may be just right for that too, but don’t expect Generac to support that method of installation. Again, despite designing for integration with its generators to extend the backup capabilities of the PWRcell, Generac does not officially endorse the use of PWRcell in off-grid solar setups.

    The tradeoffs here are a somewhat higher price than the batteries from Tesla and LG, and the missing end-of-warranty capacity guarantee. Still, if you’re looking for a robust home battery system and you need to run critical appliances like a well pump, sump pump, and A/C during an outage, the PWRcell is one of the best batteries on the market.

    Find out if going solar and installing a solar battery like the Generac PWRcell is right for your specific home by using our solar panel cost and savings calculator below.

    Find out how much a solar system would cost for your specific home
     - Author of Solar Reviews

    Ben Zientara

    Solar Policy Analyst and Researcher

    Ben is a writer, researcher, and data analysis expert who has worked for clients in the sustainability, public administration, and clean energy sectors.

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