Ever since its inception in 2003, Tesla has positioned itself as an industry-leading producer of affordable electric vehicles. Elon Musk, the (sometimes controversial) CEO of Tesla, is an ardent promoter of clean energy and sustainability. In 2015, the automaker entered the home energy storage market with their home battery, the Tesla Powerwall. Powerwall is one of Tesla’s scalable energy products, aiming to provide a simple and easy solution to common energy storage needs.
In this blog, we’ll answer some of the typical questions homeowners have regarding Powerwall, and cover all the features and specs that truly make it one of the best battery backups available on the market.
What Is a Tesla Powerwall and How Does It Work?
Tesla Powerwall is a hybrid solar battery and inverter system. It’s a lithium-ion battery system that stores energy and detects outages to automatically power your home when the grid goes down. The energy produced by your solar panels during the day is stored in the Powerwall for use in the evening and early morning. If you own a Tesla car, you can also use the Powerwall to charge it.
The Powerall system can work both with and without a solar panel system.
PowerWall With Solar Panels
When the sun is up, the home gets powered through solar. In case additional power is required, the power from the utility grid can be utilized. The Powerwall is charged during the day when your solar panels generate more electricity than is being consumed. The excess energy is stored by the Powerwall so that it can power the house when the solar panels aren’t producing electricity at night or the grid goes offline.
The cycle continues when the sun comes up the next morning.
Powerwall Without Solar Panels
Powerwall can find energy savings even when it is not paired with solar panels. If the electricity rates in your area fluctuate all through the day, your Powerwall will charge when the rates are low and discharge the energy when the rates go up, so you use the stored (cheaper) energy, rather than drawing the more expensive energy from the power grid. It also detects power outages and automatically becomes the main source of power for your home when the grid goes down, providing quick backup.
Powerwall Tech Specs
Total energy capacity
7kW peak / 5kW continuous
Depth of discharge
Round trip efficiency
45.3″ L x 29.6″ W x 5.75″ D
251.3 lbs / 114 kg
Floor or wall mount
Let’s dig deeper into these specs.
Powerwall Power Capacity
The power capacity determines the maximum amount of electricity your battery can store on a full charge. The Tesla Powerwall is currently available in only one size of 14 kilowatt-hours (kWh). This is the total energy capacity. 13.5 kWh of the 14 kWh stored is usable. This is about half of the daily electricity usage in a typical household in the U.S.
Powerwall Power Rating
In addition to the power capacity, another important metric is the power rating, which tells you how much power a battery can deliver at any point in time. In other words, the power rating indicates how many appliances it can power at the same time. The Powerwall comes with a maximum power rating of 5 kilowatts (kW), which is standard for lithium-ion batteries. With this power rating, one Powerwall is enough to run small 120-volt appliances, lights, and emergency circuits.
Powerwall Round Trip Efficiency
The round trip efficiency, also called AC/AC efficiency, measures the amount of usable energy compared to the amount of energy it took to store that energy. A higher round trip efficiency means that the battery is more efficient at converting incoming electricity into stored electricity and then back into usable electricity. The Tesla Powerwall has a round trip efficiency of 90%, which is one of the highest in the industry. So, for every 10 kWh sent to your Powerwall, it will provide 9 kWh output for future use.
Powerwall Depth of Discharge
Depth of discharge (DoD) helps in evaluating the performance of a solar battery. It is the percentage of the battery’s energy that has been discharged, compared to the overall capacity of the battery. A higher depth of discharge means the battery will last longer. This is because every time a battery is charged, discharged, and recharged, its useful life decreases. The Tesla Powerwall has a remarkable 100% DoD, which means it can pull out the entire 13.5 kWh capacity if required.
Powerwall Dimensions and Weight
The Tesla Powerwall measures 45 inches tall, 30 inches wide, and 6 inches deep and weighs 251 pounds. The sleek, compact design, along with floor and wall mount options, allows you to store more energy while taking up less space.
A Powerwall installation includes at least one Powerwall and an additional Tesla Backup Gateway system, which provides energy management and monitoring for solar self-consumption, time-based control, and backup operation. It controls the connection between the Powerwall system and the grid, and allows you to monitor energy use through the Tesla app on your smartphone. The Backup Gateway also automatically detects outages and immediately provides backup power.
The Tesla Mobile App and Customizing Your Powerwall
You can easily manage your Powerwall from the Tesla mobile app, available for both Android and iOS. This is the same app that allows customers to manage their Tesla vehicles, and it allows you to monitor your Powerwall in real time. The ‘Power Flow’ option shows you how much energy is stored or discharged by Powerwall, used by your home, and exported/imported from the grid. Through the app, you can also choose an operating mode for your energy storage system. To select an operating mode, go to the ‘Customize’ section of the Tesla app. There are three different modes available according to the specific needs of the customer. These are:
- Self-Powered Mode – Self-Powered mode stores any solar energy produced and not used during the day to power your home at night. The Powerwall charges during the daytime when excess power is generated. Once the battery is fully charged and there is enough energy produced to offset your consumption, the excess energy is sent back to the grid. In the same way, if you’re consuming more power than is being generated and stored, you will draw energy from the grid. This mode is ideal for those who want to reduce their carbon footprint and become more energy independent. This mode isn’t available if your Powerwall is not paired with solar panels.
- Backup-Only Mode – Backup power mode, which is stated as Backup-Only in the Tesla app, conserves 100% of the energy generated to provide backup power in case of an outage. During an extended outage, the Powerwall can recharge itself from the solar power system. If you don’t have a rooftop solar energy system, the Powerwall will charge itself from the grid. So, unlike self-powered mode, you don’t require your Powerwall to be paired with solar panels to switch to this mode.
- Time-Based Control Mode – This mode is useful for those who live in areas with time-of-use utility rates. Time-of-use plans are utility rate structures where electricity rates vary based on the day, time, or season. This structure divides the day into three sections:
- Peak: High electricity demand and high prices.
- Off-Peak: Low electricity demand and low prices.
- Shoulder: All other times.
Powerwall uses energy forecasting to learn your energy use patterns and the solar energy system’s production. This forecast allows Powerwall to create maximum savings for you. When set to the time-based control mode, Powerwall charges during the peak hours, when electricity costs are low, and discharges when the electricity costs are high.
There are two different ways in which the time-based control mode can operate: Balanced and Cost-Savings.
The balanced mode prioritizes charging during the off-peak times and using stored energy during peak times. This option is available only when your Powerwall is paired up with solar. The cost-savings mode, on the other hand, optimizes for maximum savings but may reduce your self-powered score. It is available even if your system is not paired up with solar panels.
How much does the Tesla Powerwall cost?
The price of one Powerwall as listed by Tesla is $7,000. The whole system will cost a total of $11,500, which includes the $3,500 Powerwall installation cost and $1,000 Backup Gateway cost. Most homeowners choose to buy two Powerwalls, in order to meet their full energy requirements. The installation cost of the Powerwall battery system falls to $3,000 if one chooses to install two Powerwalls instead of one. Up to ten Powerwalls can be installed in parallel to maximize storage capacity.
Does Tesla Powerwall Qualify for the Federal Tax Credit?
Yes! Tesla Powerwall qualifies for the Federal Solar Investment Tax Credit, at the 22% rate for 2021, if it is paired with an existing solar panel system or installed with a new one. It does not qualify for the incentive when installed without solar or if solar is installed after Powerwall. The Federal Tax Credit will reduce your federal tax liability on a dollar-to-dollar basis, up to 22% of the total cost of installation. There is no upper limit to how much credit you can claim.
Let’s understand this with the help of an example:
If you install one Powerwall system, costing $11,500, you will receive $2,990 back in federal tax credits, thereby reducing your system’s cost to $8,510.
Now is the best time to install solar panels and Tesla Powerwall because the federal tax credit will expire completely for residential energy systems in 2022. Homeowners who install Powerwall or solar panels after 2021 will not receive any federal tax credit.
Residents of Oregon are also eligible to receive a cash incentive of $300 per kW up to $2,400, on top of the federal tax credit. These incentives combined make switching to solar more affordable than ever.
Tesla Powerwall comes with a 10-year warranty that guarantees the battery will operate at a minimum of 70% of its initial capacity after 10 years. So, you can expect its storage capacity to be no less than 9.45 kWh at the end of the warranty period. All rechargeable batteries deteriorate over time as they go through multiple cycles of charging and discharging. However, a minimum of 70% retained capacity after 10 years provides remarkable value for your money. If your Powerwall fails to perform up to standard, Tesla will either repair/replace your battery at no cost, or refund your money back.
Tesla Powerwall has taken home energy storage to a new level. Powerwall 2.0 was a huge leap forward from the first-gen Powerwall that provided half the storage capacity and needed a separate inverter. The latest Powerwall has an energy capacity of 13.5 kWh, which is ideal for modern homes. On top of that, it comes with a great warranty, two mounting options, a liquid cooling system, and its own monitoring and customization options through the Tesla app.
Honestly, we believe Tesla Powerwall is a truly versatile battery that is a worthwhile investment for most homeowners due to the immense value it provides. There are already over 100,000 Powerwalls installed, making it the most popular battery choice.
You can book a free solar audit with Smart Solar Energy Co. to learn more about the right number of Powerwalls required to fulfill your specific energy requirements and available incentives.