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Tesla Powerwall 2: We review the data and functions you need to read about the leading home battery

Updated: Feb 2, 2021

Learn about the Tesla Powerwall 2 the leading home solar battery
Tesla Powerwall 2: The details, data, and functionality you need to know

Tesla Powerwall 2 Introduction:

When people think about home solar batteries, the first name that usually comes up first is the Tesla Powerwall. The Powerwall is now on the second generation. The Powerwall 2 comes with new battery technology and features to help improve functionality for homeowners. Like the Model 3, Powerwall 2 is Tesla's first real attempt at a mass-market product.

The specs of the Powerwall 2 are very impressive, a AC energy storage system that has a usable capacity of 13.5 kilowatt-hours. The Powerwall 2 inverter set up can deploy 7kW of peak AC power or at a 5kW continuous rate. If a homeowner needs additional functionality to address a larger power appliance or extend coverage during a power outage, additional Powerwall 2s can be installed to address the home's needs.

When looking at batteries, an essential factor is the round trip efficiency. The efficiency is rated based on how much power is lost between when produced, gets into the battery, and can be deployed from the battery. The Powerwall 2 has a round trip efficiency of 90%, which is towards the top of mass-market residential energy storage.

When looking at a battery, one of the most the import data points to looks at is the kilowatt-hours of the product. To make a product seem more impressive, some battery manufacturers list the total capacity of a battery's cells instead of a battery's usable capacity.

Tesla is very aware of this fact and lists the USABLE capacity of the battery. This means that 100% of the listed 13.5 kWh usable capacity can actually all be utilized when needed by the home.

Every year energy storage becomes a more critical feature of the residential solar space. In some markets, like Hawaii, batteries are now a mandatory part of a solar installation. Not only does the Powerwall 2 help consumers fight utility rate changes, potentially save more money when installing solar and avoid blackouts, but they can even help utility grids become more resilient. Let's take a look at what the Powerwall 2 offers homeowners looking to add energy storage to a solar panel installation.

Tesla Powerwall 2 AC Battery and Efficiency
Tesla Powerwall 2 Battery Information

The Tesla Mobile App:

Depending on how a homeowner purchases the Powerwall, they will utilize the Tesla mobile app to manage the battery. The app is available for both Android and iOs app store. People who already own a Tesla Model S, 3, X, or Y use the same app as their car key and for monitor charging.

Within the application, a homeowner has live updates on the state of charge of the Powerwall and change any setting related to the Powerwall.

The application gives homeowners visibility into electricity flow from the rooftop solar, the Powerwall, grid, and into/out of the home. The flow of electricity is depicted utilizing graphics and animations to simplify the information and help users understand how the system performs.

If users are looking to get a more robust understanding of the home battery's performance, they can also do that in the app. The app provides access to graphs on each energy source production and visualization into when electricity is being consumed or generated. This information can be vital in locations where utilities utilize a time of use billing structure. The application allows homeowners to change usage patterns to improve the return on investment for their solar and energy storage.

Powerwall Operating Modes:

Tesla Powerwall 2 Settings (Backup, Self-Powered, Time-Based Control)
Tesla Powerwall 2 Settings

Like its cars, the Tesla Powerwall 2 can do over-the-air updates to ensure that the Powerwall has the most up-to-date functionality. By ensuring the Powerwall 2 has internet connectivity, the Powerwall Backup Gateway 2 can be adjusted based on electricity costs, utility policies, and power outages. By leveraging the available data from the deployed Powerwalls, a homeowner can pick from a few optimized settings to get the most from their Powerwall 2.

Self-Powered This mode is designed to maximize the self-consumption of the solar produced at home. To accomplish this, during the day, the Powerwall 2 is first filled by solar power before the solar energy flows into the house. At night, the stored energy is deployed from the battery into the home, limiting the need to pull electricity from the utility grid. When set up for Self-Power, the battery can be set up to keep a reserve of anywhere between 0-100% for power outage situations.

Backup-Only One of the most appealing aspects of a Residential battery backup solution is utilization to provide backup power during a utility outage. Not only does the Powerwall 2 provide backup power, but when combined with solar can recharge itself with a homeowner's solar. If the solar system is sized correctly and the homeowner manages their electrical usage, this gives a home the capability to have power even if the utility grid goes down for hours, days, or weeks. In Backup-Only, the Powerwall can be set up to reserve 0-100% of power for backup functionality.

Advanced Time-Based Control Utilizing its internet connectivity gives Powerwall 2 the ability to optimize when it deploys electricity to help optimize the value of the electricity produced and stored by the solar system. The battery intelligently charges and discharges when the price depending on the cost of electricity. This ability is vital in utilities with a time of use rate structures like in California under NEM 2.0.

Within the Advanced Time-Based Control, Tesla gives homeowners two options a balanced mode or a cost savings mode.

Balance mode focuses on the solar and battery system utilizing stored solar power in the home when electricity from the utility is at it's most expensive and when the sun goes down.

Cost-saving mode is designed to utilize the battery's power to minimize a home's utility electrical usage and reduce the amount of utility electricity a home uses as much as possible.

In addition to the optimization modes, the Powerwall 2 also has modes for some situations that are more regionally specific.

Grid Services Because of our partnership with Sunrun, in some markets, the Powerwall 2 can unlock access to utility Grid Service programs like the Kukui Hele Pō in Hawaii. Grid service programs allow the utility to utilize the power stored in a residential battery in exchange for additional compensation. The batteries' power can be used to help stabilize the grid, avoid the need for costly power plants, and reduce the likelihood of blackouts.

Storm Watch By utilizing online storm information, this setting can determine when a storm is approaching a house and adjust to keep energy stored in the Powerwall. In high storm regions, this option can even fully charge the battery to ensure the home has full access to backup power in an outage case. This function can also be deactivated if desired.

Tesla promises more updates like this as more batteries are installed across the country.


Tesla has long been known for its battery technology. Although they have done a lot to optimize their battery's performance, the lithium-ion battery chemistry they use is one of the most common for residential home solar batteries. More specifically, the Powerwall two is a lithium nickle manganese cobalt oxide (NMC) battery. This information is important for customers to keep in mind because, at their price point, LFP batteries have some of the highest energy density (the amount of energy that can be stored in physical space) and the best safety of any battery chemistry. If you would like to learn more about the different residential battery types, check our guide to residential battery types.

Technology Advantages:

In addition to the expertise that Tesla has gained from the first generation of the Powerwall, the companies' automatic history has also given it the ability to incorporate critical technological advantages. One of its unique developments is its preconditioning functionality.

Because the Powerwall 2 is the only residential battery with a full liquid thermal management system, The liquid cooling system is fully enclosed and circulates 2.4 quarts (2.3 LO) of liquid coolant to ensure the battery can stay as close as possible to ideal temperatures.

This thermal management allows the battery to operate at the broadest range of temperatures for a residential battery -4°F to 122°F. It also helps protect the battery because temperature swings can harm a battery's efficiency, reducing useable storage and lifespan.

Due to its internet connectivity and the ability to optimize battery performance based on real-time data, the liquid coolant system improves its efficiency. The Powerwall 2 can start warming the battery up before sunrise during cold nights to help ensure the battery is at an ideal temperature to start receiving a charge when the solar system starts working.

Powerwall Gateway 2:

What makes the Tesla Powerwall Gateway 2 Such An Important Part of a Home Battery
Tesla Powerwall Gateway 2 Overview

We have spent a lot of time discussing the importance of internet connectivity and updating as new programs and information become available. Making the Powerwall 2 a "smart battery" unlocks more value for homeowners and helps to optimize a home's solar and battery system. The brains of the Powerwall and what allows it to optimize and improve is the Powerwall Gateway.

In 2019 Tesla upgraded to the Powerwall Gateway 2. The Powerwall Gateway 2 is a marked improvement from the first generation of the product for various reasons. Unlike the first-generation product that was an ugly grey box with antennas sticking out to improve cellular and WiFi communication and an ethernet plug inside in case of emergency, the Gateway 2 is designed to look like a mini Powerwall.

The Gateway 2 is more expensive than the first-generation product, but by upgrading the internal communication components and the aesthetics, the new product helps improve the long-term value and performance for Powerwall 2 customers.

The Powerwall Gateway 2 is the brains of the battery, and the investment that Tesla has made in the product shows that they understand that residential energy storage is an evolving market. By upgrading the component that unlocks homeowners access to future programs and savings, they are improving the customer experience with the Powerwall 2 today and in the future.


Overview of installation information for Powerwall 2 home solar battery
Tesla Powerwall 2 Installation Details

When looking for a home location to install the Powerwall, it is important to keep in mind that it must either be ground-mounted or mounted on the wall. Part of the site survey process is to identify the best location for the installation, to increase the battery's efficacy, reduce costs and protect the battery's cells, but it is always good to let your consultant know if you have any preferences on the location of the battery.

We usually recommend a location that is as close as possible to the solar installation and electrical panel. The Powerwall 2 is touch-safe and also designed to be water-resistant and dustproof. This allows more installation flexibility and helps to avoid the need for special clearances or safety measures.

Like other batteries, the Powerwall 2 has an optimal temperature range between 32°F to 86°F (0°C and 30°C). It can operate between -4°F to 122°F (-20°C to 50°C), but in extreme temperature, the efficiency will decrease significantly, and the longterm lifespan of the battery may be impacted. Because of the importance of maintaining the optimal temperature range, installing the product in a garage may make sense if you live in a location with more extreme temperature swings.

At Alchemy Solar, we only use installation partners who are approved and vetted to install the Powerwall 2. We highly recommend that anyone interested in the product does the same. Even though the product's design is very sleek and might remind you of an Apple product, this is a massive battery that will be going near your electrical panel. When installed by a professional, issues like wiring, local code, or even flooding will not be an issue, but if installed by someone who does not know what they are doing, it could be dangerous.

The PowerWall 2 is an extremely heavy product and weighs in at 269 pounds (122 kilograms). It has a height of 45.3 in x width of 29.7 in x depth of 6.1 in (1150 mm x 755 mm x 155 mm), allowing for the flexibility to install on the wall or ground. The density of the batteries does mean it usually requires a team of two or more to install the product, and usually, special transportation equipment is needed to move the battery to the desired installation location safely.

Depending on what the use case for the battery will be, additional equipment will also be needed. If the battery is used as a backup power source for essential loads, the installers will need to install a new sub-panel to connect the Powerwall 2 to the specific circuits in the home that it will backup during an outage.

The Powerwall 2 does have the ability to do full home backup, but the feasibility of this will depend on the home's electrical load and usage patterns. If a homeowner can use the Powerwall 2 for full home backup, the Powerwall and Backup Gateway will be wired directly to the main electrical panel.

Tesla Powerwall warranty coverage:

  • Warranty period: 10 years

  • Guaranteed end of warranty capacity: 70%

Tesla Powerwall 2 offers a 10 year and 70% capacity warranty on it's battery
Tesla Powerwall 2 Warranty

For most homeowners, the Powerwall 2 will be designed to go through one cycle of charging and discharging a day. Tesla provides a 10-year warranty on its product and guarantees that it will maintain at least 70 percent of its ability to hold a charge through those ten years.

Like other batteries, over time, the Powerwall will lose some of its ability to hold a charge. Most of you have experienced this with laptops or smartphones, but the critical thing to keep in mind is the company backing the warranty.

2020 was a year of massive financial growth for Tesla and put them on the road to financial stability, something they had struggled with in the past. The 70% capacity and the financial backing of Tesla means that the Powerwall 2 warranty is one of the more robust energy storage spaces.

Powerwall Price, Rebate, Incentives:

The Powerwall 2 can only be purchased and installed by approved vendors, and unfortunately, many companies advertising the Powerwall do not have the required certification. The Tesla Powerwall 2, like some other Tesla products, has had issues with availability. At Alchemy Solar, we make sure to partner with companies who can consistently obtain the product, but it is good to be prepared for a longer installation timeline than other home solar battery options.

The cost of installing the Powerwall 2 is varies based on a variety of factors. The Cost of Powerwall 2 on its own is around $6,500, and the Powerwall Backup Gateway 2 costs $1,100. Additional hardware, permitting, and installation costs usually cost around $3,0000-5,000. Fortunately, Alchemy Solar has various finance options and is partnered with the Power Purchase Agreement leader Sunrun to offer the Powerwall 2 with $0 down and no upfront cost to homeowners in specific markets.

When charged with solar, Powerwall two also qualifies for various rebates and, when charged with solar panels, the Federal Solar Tax Credit. For example, in California, some homeowners can qualify for the Self-Generation Incentive Program, reducing the cost of installing the battery significantly.

Alchemy Solar Powerwall 2 advantage:

The Powerwall 2 is one of the most in-demand products for customers looking at home solar and energy storage. Unfortunately, many solar companies use this customer excitement to utilize disingenuous marketing techniques to sign up for agreements that do not address the customers' wants.

At Alchemy Solar, we only partner with installers who have been certified to install the product. Being a certified Poerwall installer is important because Powerwall 2 is complicated, expensive, and designed to provide backup power during a power outage. We want to make sure our customers have a battery that lasts for the entire warranty timeline and keeps homeowners safe during a power outage.

The other important factor is product availability. Because Alchemy Solar only partners with the nation's leading solar companies, our partners have access to the Powerwall 2. We cannot guarantee that the product will always be available, but we are confident that when the Powerwall 2 is available, our partners will be at the head of the line.

We also understand that the Powerwall 2 or other energy storage options can be an expensive addition to a solar panel system. We have access to some of the industries leading finance options like Sunrun with its $0 down BrightBox option, LoanPal, Mosaic, and many more to make sure that we can accomplish your financial goals.

If you are interested in learning more about the Powerwall 2 or if energy storage and solar is a good fit for you, please schedule a free consultation with Alchemy Solar today.

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