If you are looking at purchasing Tesla solar panels or having the company replace your traditional roof with a brand new solar roof, you probably have been discussing Tesla’s Powerwall 2. This device stores your solar energy during off-peak hours, when energy prices are low, so you can use that energy later when prices are at their highest cost.
In October 2016, Tesla unveiled its Powerwall 2, the successor to its original battery storage device, the Powerwall. A Powerwall gives you energy independence by storing energy you can use later so you do not need to rely on your energy company. But, is the newest, latest Powerwall battery device worth the extra price? Read on to find out.
Why You May Need a Solar Battery Device
There are numerous reasons why individuals decide to go solar, whether it is with solar panels or a solar roof. Not only does solar energy ensure you are using clean, renewable energy to power your home. Over time, you can save money on your electric bill because you are powering your home with the sun, not electricity from the grid.
One reason to purchase a Powerwall is for energy independence during a power outage. Even with solar energy, if your power goes out so does your solar since it needs the grid to power your home. This is where the Powerwall comes into play – if your power goes out, the Powerwall will kick in and power your home with stored energy.
The second reason to purchase a Powerwall battery device is for the added energy savings on your electric bill since it stores energy more efficiently because of how it times energy storage. Tesla’s Powerwall stores energy from the sun during the day when energy is in low demand and, in turn, is less expensive to store in the battery.
When you get home at night is when energy is at its most expensive rate to use because these are peak hours when energy demand is high. You cannot use solar energy now because the sun went down, so you can use the stored energy in the Powerwall to inexpensively power your home. These are the main benefits:
- Save money on your electric bill by storing energy during off-peak hours and then discharging it during peak hours
- Reduce your carbon footprint by using clean, renewable stored energy
- Have the peace of mind you desire during a power outage by having energy independence
The Powerwall 2 Has Benefits Over the Original Powerwall
The latest Powerwall version from Tesla does transform how a battery can store solar energy for your home. The first version of this Powerwall was an affordable energy storage option, offered a DC-coupled battery, and a 6.4 kilowatt hour capacity. This first generation Powerwall made waves as a unique, high-voltage battery for the home.
The use of the Powerwall was also attractive; not only were your Tesla solar panels or solar roof garnering energy from the sun to provide power to your home, but energy was now stored for later use. This exceptional aspect of time-related power storage brought a new world of energy-related savings to the mainstream in solar and non-solar homes.
This means the Powerwall had the ability to power your home when the sun was not shining and energy rates were at non-peak hours. However, the original Powerwall was smaller than other battery versions, which meant the amount of power stored would more than likely not give your major appliances continuous power during an outage.
The Powerwall 2 has changed this amount of kilowatt power and has really taken battery storage issues to the next level of storage space. This amount of storage is just one of the different ways Tesla has improved the Powerwall 2 over their original model. However, this also comes at a price – $8,500 just for the device itself before installation.
Storage for the Powerwall 2 is Double the Capacity of the Powerwall
If you have a larger home or family to power throughout the day and night, the Powerwall 2 will benefit you more than the Powerwall. The storage capacity of the Powerwall 2 has doubled from the original Powerwall, from 6.4 kilowatt hours to a massive 13.5 kilowatt hours of functional energy storage capacity to power the home.
This larger storage capacity is a chief benefit of the Powerwall 2 over the original Powerwall in that you can now cover nearly half of your home’s daily energy usage in one device. This larger amount of kilowatt hours is one of the uppermost usable capacity ratings for solar batteries today. However, do you need that much power?
In order to take full advantage of this larger storage capacity, your home will need to produce more than 15 kilowatt-hours of power to fully charge the Powerwall 2. You can check your electric bill to see how much energy your home produces a day. If it is under that number, the smaller Powerwall may be just fine to store energy for the home.
If you have solar panels, you will need to make sure you have enough on your roof – probably five or more kilowatts of solar panels during the day – to fully charge the Powerwall 2 device. That being said, the smaller Powerwall probably will not generate enough energy to run your major appliances during an outage like the Powerwall 2.
Larger Storage and More Power With the Powerwall 2
The Powerwall 2’s 13.5 kilowatt hours of functional energy is 100 percent depth of discharge. Not only that, but the device handles an impressive 7 kilowatts of power (charge and discharge) capacity, 5 continuous, and 14 kilowatt-hours of energy storage. Since the average family uses 30 kilowatt-hours per day, more power is welcomed.
How do the specs compare now that a new Powerwall is on the market? You can take a look for yourself and see if the Powerwall 2 is indeed worth the price. Just remember that the Powerwall 2 is more than double the size of the original Powerwall. This means more energy needs to be put into the batteries to fully charge it to the 13.5 capacity:
- 13.5 kilowatt hours of energy capacity means it will store the proper amount to run your major appliances for a full day
- The depth of discharge is 100 percent
- Round trip efficiency is at 90 percent
- 7 kilowatt peak power, 5 kilowatt continuous power
- Seamless backup transition
- Lithium nickel manganese cobalt battery chemistry
- Pure sine wave output
- Floor or wall mount
- Indoor or outdoor placement
- Works in impressive temperatures – -4 degrees to 122 degrees Fahrenheit (which equates to -20 degrees to 50 degrees Celsius)
- 10 year warranty or 37.8 megawatt-hour (MWh) throughput
Looking at the specs above, the Tesla Powerwall 2 is an impressive option for a solar battery storage system that is much larger than its predecessor. This second-generation battery works well for residential homes that can fill the 13.5 kilowatt capacity so that there is enough stored energy for high-peak hours or during a power outage.
If you combine Tesla’s Powerwall 2 with solar, the battery could power your home for approximately twelve hours. If you are not using a solar system, you will possibly need more than one Powerwall 2 – maybe even three or more – to power your home for an entire day. Two batteries will power a home for eighteen hours without a solar system.
What About the Warranty – is the Powerwall 2 Better?
The Powerwall 2’s warranty is comparable to other home-based batteries. This new warranty is ten years with 70 percent minimum retained capacity, which is better than the Powerwall 1 warranty. If you are charging your Powerwall 2 completely by solar power, it is unlimited in both kilowatt-hours and cycles, but not if you do not have solar:
- Ten-year warranty for the Powerwall 2, or
- 37,800 stored kilowatt-hours in lieu of unlimited solar power.
If you charge the Powerwall 2 using solar and low tariff energy that is also off-peak, the number of daily cycles may be more than one, which can increase the possibility of cell degradation. Other factors that will cause cell degradation include the depth of discharge, the total number of cycles, the rate of charge, and the operating temperature.
Remember that if you want a warranty that is unlimited through Tesla, you must use the Powerwall 2 100 percent with a solar system. That being said, the Powerwall’s degradation rate is 12 percent after 1,250 cycles, which means the total degradation after ten years would be outside of the warranty limit: 35 percent versus 30 percent.
In addition, most batteries will slowly degrade in capacity over time from the continuous storing, charging and discharging of energy into the home. Lithium batteries, like the one used in the Powerwall 2, will usually have reduced their retained capacity to around 60 or 70 percent after ten years (and this is when the warranty is null and void).
Time-Based Control Options Are Not Unique, But Still Impressive
The time-based control element may not be unique to the Powerwall 2, but it is impressive when reviewing the monitoring that comes along with it. The battery is continuously operating an energy forecast of the home, which is useful when examining your home’s energy usage and optimizing the solar capabilities to maximize savings.
How does this work in the new Powerwall 2? The energy forecast will show you when your home is using energy at the higher-costing times of the day and then prioritizes charging during the lower-costing times. The Powerwall 2 will then discharge the stored energy during high-cost periods so that you are saving money on your energy bill.
The Powerwall 2 offers two types of time-based control functions:
- Balanced version of time-based control will charge the Powerwall 2 by using the excess solar energy your battery accumulated during off-peak and shoulder hours and then discharges the energy during high-peak, more expensive hours. It essentially balances sustainability and cost savings by reducing your peak usage and maintaining a high self-powered score. This can only be used with a solar system.
- Cost-savings version charges from the excess solar your battery stores during off-peak and shoulder hours, but does not need to be used with a solar energy system. That means this version does maximize savings, but not the self-powered score as with your solar panels or solar roof.
This means you can optimize your family’s energy usage so that you are charging your Powerwall 2 during the less expensive, off-peak hours and then using this stored energy during the more expensive, peak hours of the evening when energy costs the most. And since the Powerwall 2 is much larger than the Powerwall, that is more energy to use.
- prioritizes its use of stored solar energy to power the home when electricity is expensive
- powers the home from the Powerwall 2 after the sun goes down and the sun is not able to power the solar panels
- Minimizes the home’s usage profile to keep the electric bill costs down and your carbon footprint in check
- optimizes the storage and usage of electricity
If you are using Tesla solar panels or their solar roof, they will first absorb the sunlight to create what is called DC electricity. This is then converted to AC electricity through an inverter which is either used or stored in your Powerwall 2 and managed through its cloud-based app. This is another function that makes this new version impressive.
An Integrated-AC Battery Saves Time and Money
When your solar panels produce electricity from the sun’s rays, it comes out as direct current (DC) power. However, your home’s major appliances run on alternating current (AC) electricity. Therefore, you need an inverter to convert the energy produced by the solar panels from DC to AC. The Powerwall 2 has a fully-integrated AC battery system.
The original Powerwall needed a separate inverter to convert this DC energy into AC electricity that could be stored in the battery for later use. This separate device added more time, and more expense, to the customer during the installation process. The new Powerwall 2 offers an integrated inverter built into the battery to save these expenses.
The Powerwall 2 comes in two different varieties – an AC-coupled version that includes the inverter and a DC-coupled version that does not. If you choose the first version, you get essentially an all-in-one model that internally converts the DC energy to the AC energy needed. This integrated system has other benefits over the original Powerwall:
- A unique aspect of having an AC-coupled battery with an integrated inverter/charger
- In most cases, you do not need to purchase an additional inverter to convert your energy into usable power
- The Powerwall 2 can be retrofitted pretty seamlessly into homes that already have solar installed
- The integrated inverter can be installed in homes without solar capabilities so that the Powerwall 2 is simply used as a backup for power during outages
- Protected by a 12.5-year manufacturer’s warranty, which is nearly three years longer than the 10-year inverter warranty that is the industry standard
The Powerwall 2’s fully-integrated AC battery system also gives you more flexibility of where you can place the battery system in your home. You can have the Powerwall 2 installed indoors or outdoors, on the wall or on the floor, it does not matter since the inverter is integrated into the system itself for more flexibility as well as more power.
Flexibility is a Main Advantage of the Powerwall 2 Over the Powerwall
As noted above, the Powerwall 2 can be installed outdoors or indoors, which means it is water resistant, dust proof, and can handle all weather-related conditions. It is also easier to install and more suitable for places inside the home since it can be mounted on the wall or on the floor. This is because of the brand new design of the Powerwall 2.
Some Tesla customers have complained that the original Powerwall was more aesthetically-pleasing with its rounded edges and turtle-shell looking exterior. The Powerwall 2 has been said to look too boxy, but Tesla has explained its reasoning behind the new look. Again, it all comes down to making the device more flexible.
The curvier exterior of the Powerwall definitely looked sharp in the home, but it could not hold the weight of the battery. This meant the Powerwall had to be mounted on a wall, which limited the space and orientation of where you could place it in your home. The hard right angles and rectangular shape are why ground mounting is possible.
The flatter design of the newer Powerwall 2 also gives customers the ability to stack units back-to-back. This means you can double up on more devices without losing more wall space. In fact, up to ten Powerwall 2 batteries can be installed together at one location if your home has the larger amount of energy needs to be fulfilled.
Monitoring Your Energy Usage is Even Easier with the Powerwall 2
Not only does having an AC-coupled, integrated inverter give you more flexibility and ease; it also gives you a complete and seamless monitoring and control system through a Tesla app interface to manage your energy anywhere at any time. This means you do not even need to be home to see how your home produces and uses its solar energy.
This compatible Tesla app helps you monitor your energy usage in real time as well as document your savings. The app has a backup-only option to amplify protection during an outage, and the area “Power Flow” from the home screen shows how the Powerwall is working with your home, your solar system, and the grid by graphing the following:
- How many kilowatts your house is using
- How many kilowatts your solar system is producing
- How many kilowatts is actually going into the Powerwall for storage and out of the Powerwall for energy consumption
- How many kilowatts is being pulled from or sent to the grid
These energy screens show your daily and weekly activity, as well as historic looks at the past days, weeks, months, and even years of energy activity. This app is very useful for recording your daily energy activity to see how exactly your home uses the solar energy being produced by your solar system and stored into the Powerwall for later use.
This Tesla app allows you to customize your Powerwall 2 based on your home’s particular needs. For example, if you are pairing the system with solar, you can use “self-powered mode,” which stores solar energy not used during the day to power your home at night and exports excess energy to the grid if the Powerwall 2 is fully charged.
The Powerwall 2 has a Notable Advanced Cooling System
The Powerwall 2 is literally cooler than the Powerwall 1 due to a new, advanced liquid cooling technology system. This liquid thermal management system allows the system to function in a much wider range of temperatures – from negative 4 to a whopping 122 degrees Fahrenheit – because the battery keeps its temperatures stable over time.
This liquid cooling system protects the battery device from power deration or reduction when temperatures hit above 104 degrees Fahrenheit, which is normal for batteries that are lithium-ion based and used in hotter areas of the world. The cooling system allows the Powerwall 2 to release more heat under high loads and during rapid charging.
This liquid cooling system protects your battery in extreme heat and will also enable the battery to charge at temperatures that reach below freezing. Other lithium-based batteries would undergo harshly-reduced charge rates when the temperature drops, and most cannot even charge properly below 41 degrees Fahrenheit.
The Powerwall 2 can precondition, which means it preheats the cells at lower temperatures so that its charging performance is improved when the temperatures fall towards freezing. The advanced liquid cooling system allows for a longer life span of the Powerwall 2 versus its competitors that also have a lithium-ion based battery system.
Do Not Forget You Need to Purchase a Backup Gateway
Another possible negative is that you will need to purchase a backup gateway for backup power because the Powerwall 2 cannot perform as a backup power supply. This is because the Powerwall 2’s integrated inverter does not work on its own from the grid during an outage. It needs a backup gateway in order to provide this backup power.
This device is sometimes not calculated in the price when looking at the cost of a solar system, but it can be an expensive addition that is needed. Tesla is offering its Backup Gateway 2 for around $1,800, which performs as a management system and communications center for your household energy needs. It also does the following:
- Separates the backup circuits during a blackout from the electricity grid
- Allows your energy system to work during “off-grid” times
- Has even more advanced monitoring services and time-based controls for the Powerwall 2
- Includes a higher speed, 4G communication system that includes a three-phase operation and more accurate CT monitoring
- Looks more aesthetically-pleasing than its predecessor, which was an old, grey backup gateway box
The Backup Gateway 2 comes at a steep cost, just under $2,000, and it will not work as a dedicated off-grid power system. Therefore, you should not think about disconnecting entirely from the electricity grid just because you purchased the Tesla Backup Gateway 2. It is for short durations of off-grid mode when the Powerwall is in backup mode.
Pricing is unclear overall of the Powerwall 2 and its additional components, as some solar roof customers saw the price of their Powerwall go up after they had already signed their contracts. Others have said it has been near impossible to even get a Powerwall 2 from Tesla without also installing new solar panels or a new solar roof.
Are There Any Other Negatives Related to Tesla’s Powerwall 2?
Adding a solar battery storage system will increase the initial cost of your solar system, whether it is simply purchasing Tesla solar panels or an entire Tesla solar roof. However, the Powerwall 2 is powerful enough to save money on energy bills in the long run by timing the energy stored versus the energy discharged to power the home.
The cost of the Powerwall 2 has increased, and this does not include the cost of the gateway, installation, and any other costs that may arise. That being said, the federal government does give a 26 percent federal tax credit that can be used on the cost of the battery. Some states also offer monetary incentives to purchasing the device.
Another negative is that the Powerwall 2 can only be installed by approved Tesla installers, which means the price of installation is hard to pin down and can vary depending on location and installer. That being said, the new shape of the Powerwall 2 makes it more attractive than the original for larger homes since they can be stacked.
If your home can produce enough energy, solar or otherwise, to fill the 13.5 kilowatt hours of this larger Powerwall 2, it can be a lucrative option to power your home during peak times or a power outage. The Powerwall 2 could probably power a home for approximately twelve hours if the home consumes 28 kilowatt-hours each day.