Tesla’s Home Energy Storage System – Powerwall
Powerwall is a stationary home energy storage system that can be installed in homes to aid in solar self-consumption, time of use load shifting and backup. Powerwall is only available from certified Tesla installers and carries an industry-leading warranty.
The Powerwall features an integrated inverter, allowing households with existing solar systems to add Powerwall without dismantling their inverters. It is also capable of supporting EV charging.
Inverter
Most of us plug in a smartphone, stream music on a portable audio system product-category/powerwall or play a video game when we’re on the go. But if you want to run more elaborate devices, like a laser printer or an LCD TV, you’ll need a power inverter.
An inverter converts DC power from a battery or solar panel into AC household power for running electronic devices and appliances. Inverters are available in a wide range of output voltages and frequencies to match the power needs of various appliances and equipment, from laptop computers to hair dryers.
Inverters that produce a true sine wave output are called pure sinewave inverters, while those that only approximate the shape of a true sine wave are known as modified sinewave inverters. Both types are capable of operating at the maximum power point (MPP) of a battery, but pure sinewave inverters typically require less maintenance.
To increase the total ampere hour (Ah) capacity of an inverter set, multiple batteries can be connected together in a parallel configuration. Two batteries connected in parallel will generate double the amp hours of a single battery, while three batteries in parallel will provide triple the amp hours of a single battery. A fuse or circuit breaker is recommended to protect the inverter and cables from overcurrent, which can cause damage and/or fire. Consult your owners manual to ensure you’re using the appropriate sized fuse or circuit breaker and cable gauge for your specific inverter and power cord combination.
Rectifier
The Powerwall uses a rectifier to convert the direct current (DC) electricity stored in the battery back into alternating current (AC) energy compatible with your home’s electrical systems. This process enables the Tesla Powerwall to seamlessly integrate with your home energy systems, delivering clean, reliable energy and minimizing energy waste.
Rectifiers are essential components of high-voltage DC power supplies, providing stable, high-quality power to critical equipment. They are also used in solar, wind, and other renewable energy systems to convert harvested energy into usable forms of power. Diode rectifiers are especially important, as they can be configured to provide a wide range of different output voltages.
With the new Time-Based Control feature, the Powerwall will monitor your electricity prices and use its battery capacity to save you money on peak utility rates. It will charge when rates are low and discharge when they’re high, allowing you to take advantage of time-of-use electricity pricing and make the most of your solar panels.
The Powerwall can be installed either as a standalone battery or paired with your existing solar system, and both options are eligible for the 30% federal tax credit. You can learn more about the specifics of this credit here.
Lithium-Ion Battery
A lithium battery uses – you guessed it – lithium in metal or ion form as its anode material. This allows them to deliver more power in a smaller space, with a higher voltage than other batteries. This makes them a favorite for small electronic devices, such as smartphones and tablets, as well as medical devices. Larger lithium battery packs are also used to power e-bikes, electric scooters and vehicles.
Lithium-ion batteries are rechargeable and have the highest energy density of any battery technology. They can also withstand many charge and discharge cycles, making them very durable and reliable. They typically have a lifespan of five to 10 times that of their alkaline counterparts, which means they can be re-charged hundreds of times.
During a charge cycle, lithium ions are separated from their electrons by an electrolyte and pass through the cathode to reach the anode. This process is what creates the battery’s high voltage and charge storage per mass and volume, and it also gives a longer lifespan than other rechargeable batteries.
Nickel-Metal Hydride (NiMH) and Lithium Ion Polymer batteries are two of the most common lithium battery chemistries. The latter combines a lithium anode with a polymer separator, which allows the battery to be slim and simplified. For this reason, it can be more easily incorporated into devices and appliances such as tablets or walkie pallet jacks.
Controls
During normal operation, Powerwall will continuously run an energy forecast and learn patterns of your energy usage. Based on the forecast, it will prioritize charging from the grid during low-cost periods and discharge to avoid higher utility rates during peak periods. These priorities can be changed from the Tesla app.
A home on Time-Based Control mode is programmed to maximize energy value even during the winter season, when solar production is much lower than it is in summer. This mode allows the battery to store energy during off-peak periods when rates solar system are typically low and then use that stored energy to offset energy used during high peak rate hours.
Energy prices change throughout the day and across seasons, and Powerwall will create value for you by adjusting its charge and discharge behavior to take advantage of those changes. This technique is called energy arbitrage and is optimized by your Powerwall through an energy forecast that is tailored to your home and its usage patterns.
Your Powerwall is also designed to operate in the event of a grid failure. After the solar inverter stops producing energy, your batteries will automatically switch to a backup mode that allows the system to continue to provide energy for your house while preventing your home from exporting excess energy back to the grid. This feature can be enabled in the Settings menu of the Tesla app.