Tesla Powerwall Battery Review

Founded in 2003, Tesla has rocketed onto the scene in several markets in a short period of time. Tesla EVs, Tesla solar panels, and the Tesla Solar Roof are shaking up the world of automobiles, solar power, and energy infrastructure in general. And with their Powerwall, Tesla is also transforming the world of energy storage.

The Tesla Powerwall is a great battery option for homeowners. But determining if it is the right battery for you requires weighing its pros and cons.

Let’s take a look at the Tesla Powerwall’s pros and cons and help you determine if it is the best battery option for you.

HOW DOES THE TESLA POWERWALL WORK?

The Tesla Powerwall works like most batteries. It stores energy from a source, such as solar panels or a utility, and can provide that energy at a future time when needed.

With the rise in residential solar installations in recent years, the Tesla Powerwall has often been paired with solar panels to store excess energy production. This provides a clean source of energy that can power the home both during the day and night, on cloudy days, as well as in the dark days of winter.

The Tesla Powerwall can be used to offset Time-Of-Use (TOU) energy rates. Utility customers that are on a TOU pricing structure pay higher energy rates during peak usage times. To avoid these high energy costs, homeowners can install a Tesla Powerwall battery to store solar energy during off-peak hours and use that energy when prices are highest.

This strategy can be especially useful for electric vehicle (EV) owners. That’s because most peak hours occur during the evening, when homeowners and children are returning from work and school. This is also the time when EV owners tend to plug in their electric vehicles. To avoid the high energy prices of charging EVs during peak hours, EV owners can pull from their battery to top up their EV instead of pulling power from the utility

TESLA POWERWALL SPEC SHEET

The Tesla Powerwall has several qualities that set it apart from other top battery options and can help a homeowner choose if it’s right for them.

Let’s take a look at the basics of the Tesla Powerwall: Size, Compatibility, Chemistry, Performance. Warranty, and Cost.

See full Tesla Powerwall spec sheet here.

POWER & CAPACITY OF TESLA POWERWALL

The Tesla Powerwall comes in one size/model: the Tesla Powerwall 2.0 (released in 2016). This model of Powerwall totes a maximum power rating of 5.0 kW and 13.5 kWh usable capacity.

To better understand these numbers, let’s break down the meaning of a battery’s maximum power rating and usable capacity.

A battery’s maximum power rating (measured in kilowatts, or kW) is the maximum amount of electricity that can be output at a single time. The higher the power rating, the better a battery can power more demanding appliances. Think of maximum power as a straw in a drink. The wider the straw, the more liquid can be sucked out at one time.

A battery’s usable capacity (measured in kilowatt hours, or kWh) is the maximum amount of electricity a battery can hold on a full charge. Usable capacity determines how long a battery can power the appliances it is supplying. Think of usable capacity as the drink the straw is pulling from. The larger the drink, the larger the usable capacity.

The balance between maximum power and usable capacity is important to consider. If the battery’s maximum power is high and can easily supply power-hungry appliances, it is important to ensure the energy capacity can sufficiently supply that power for the required time. Using the drink and straw analogy, it’s important to ensure the drink has enough liquid (energy capacity) so that the straw (maximum power) doesn’t deplete the drink too quickly.

COMPATIBILITY

When looking at batteries, it’s crucial to know how the battery will interface with other equipment, such as solar panels and solar inverters.

The Tesla Powerwall is compatible with a wide range of brands (SolarEdge, SMA, Fronois, Enphase, etc.) and equipment (solar panels, solar inverters, including off-grid inverters).

Unfortunately, as of 2021, Tesla has announced that it will no longer sell the Tesla Powerwall without the purchase of Tesla solar panels or Tesla Solar Roof. This greatly limits the ability of homeowners to own a Powerwall battery system without having to install solar panels or solar panels from a different company.

The Tesla Powerwall is also AC-coupled, which means it receives charge through a different process than other batteries that are DC-coupled. AC-coupled batteries don’t receive charge directly from solar panels or the grid. Instead, the DC power from the solar panels must first be converted to AC power through an inverter, then that AC power must be converted back to DC to charge the battery.

AC-coupling has its advantages, such as easier and cheaper installation, as well as the ability to charge off both solar panels and the grid. However, AC-coupling is generally less efficient due to the added steps between power production and storage.

BATTERY CHEMISTRY

The Tesla Powerwall uses lithium-ion technology, specifically lithium nickel manganese cobalt oxide (NMC), to store energy. Lithium-ion technology has greatly improved in recent years, and it is now the preferred chemistry for batteries. This preference is due to lithium-ions’ many benefits, including high energy density, safer operation, lower maintenance, and greater depth of discharge (to be explained later).

PERFORMANCE

Two key performance indicators are important when evaluating battery options: depth of discharge (DoD) and roundtrip efficiency.

Depth of Discharge (DoD): DoD indicates the percentage of a battery’s energy that can be discharged relative to the overall capacity of the battery without damaging the battery’s cells. For instance, if a battery with 10 kWh of usable capacity can be discharged to 1 kWh without damaging the battery, that battery has DoD of 90 percent. The higher the DoD, the better the battery will perform and the longer life it will likely have.

The Tesla Powerwall has a DoD of 100 percent. You can’t get much better than that.

Roundtrip Efficiency: Roundtrip efficiency is a measure of electrical losses involved with charging and discharging a battery. The higher the roundtrip efficiency percentage, the more efficiently the battery can store the electricity it is receiving and then provide that electricity when needed.

The Tesla Powerwall has a roundtrip efficiency of 90 percent, which means that for every 10 kWh of electricity put into the battery, 9 kWh can be output. This roundtrip efficiency is among the top in the battery market, though it lags behind competitors like the LG Chem RESU 10H (with 94.5 percent roundtrip efficiency)

TESLA POWERWALL WARRANTY

The Tesla Powerwall comes with a 70 percent capacity, 10 year or 37.8 MWh energy throughput warranty. This means the Tesla Powerwall is guaranteed to produce at least 70 percent or its original capacity after 10 years or 37.8 MWh energy throughput, whichever comes first.

This is one of the strongest warranties offered by a battery manufacturer, and it beats the coverage of other competitors, such as the LG Chem RESU 10H with 60 percent capacity, 10 year or 22.4 MWh

See full Tesla Powerwall warranty here.

TESLA POWERWALL COST

While cost isn’t the most important factor when buying a battery, it is definitely a huge influence.

Thankfully, battery costs have come down significantly in recent years, which has made batteries much more affordable.

The cost of the Tesla Powerwall has increased twice within the span of a few months between 2020 and 2021. In October 2020, Tesla raised the price of the Tesla Powerwall from $6,000 to $7,000, then raised the price another $500 to $7,500 in early 2021. With the Gateway, an energy management and monitoring device, the cost before installation is $8,500 ($555/kWh). With installation the price is $12,000, not including the required installation of Tesla solar panels (as we mentioned earlier).

Luckily, a portion of this cost could be recouped through the federal solar tax credit (or Investment Tax Credit, ITC). The ITC can provide a 26% tax credit for the entire cost of a solar installation, including battery backup. Your solar provider can provide more details and ensure your system qualifies for the federal solar tax credit.

TESLA POWERWALL PROS

As outlined above, there are many advantages the Tesla Powerwall has over its other competitors in the battery market. Here is a rundown of the largest pros of the Tesla Powerwall, including some not mentioned above.

• $555/kWh price point is competitive with most major brands
• Lithium-ion NMC chemistry provides safer, more durable, more reliable battery than traditional battery chemistry
• 70 percent capacity, 10 year or 37.8 MWh energy throughput warranty beats out warranties of other batteries
• Compatible with many brands and equipment types
• Slim size compared to other batteries, such as sonnenCore
• AC-coupling provides simpler and cheaper installation
• Unbeatable 100% Depth of Discharge (DoD)
• Strong roundtrip efficiency of 90 percent

TESLA POWERWALL CONS

While the Tesla Powerwall has many impressive features, there are several disadvantages it has compared to other top battery competitors.

• Must be installed with Tesla solar panels or Solar Roof
• AC-coupling provides less efficient charging and discharging
• Recent price increases could indicate an upward trending price point

IS THE TESLA POWERWALL WORTH IT?

Determining whether the Tesla Powerwall is right for you requires weighing many factors. 

These factors can include why you want a battery. Do you want the battery for peace of mind during a power outage? Are you wishing to avoid TOU and high peak energy rates? Are you wishing to go off-grid?

It’s also important to factor in whether your utility offers net-metering, which will affect the financial viability of your battery investment.

The answer to each of these questions will certainly affect your decision. And unfortunately, these answers might not be easy to determine without the help of an expert.

Thankfully, Green Ridge Solar can help you decide if the Tesla Powerwall is right for you. We help Oregon homeowners install battery backup with and without solar panels, and we can answer any questions you might have about battery backup.

Contact Green Ridge Solar today with all your battery questions. You can even use our Solar Calculator to see if solar panels could save you money.

TRACKBACKS/PINGBACKS

1. SolarEdge Energy Bank Battery: What We Know – Green Ridge Solar – […] The Energy Bank’s 10kWh capacity is on par with the LG Chem RESU battery, which is a stiff competitor…
2. sonnenCore Battery Review – Solar Batteries – Green Ridge Solar – […] kWh can be output. This roundtrip efficiency lags behind the LG Chem RESU (94.5 percent) and the Tesla Powerwall…
3. SolarEdge Energy Bank Battery Review – Solar Batteries – Green Ridge Solar – […] output. This roundtrip efficiency is on par with the LG Chem RESU (94.5 percent) and beats out the Tesla…