The Tesla Powerwall: How it Works

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Although Tesla is known for its electric vehicles and other cutting edge innovations, its solar product line has gained significant traction. Many people are excited about the company’s solar shingles and home battery.

Although solar shingles are struggling to take off, the home battery is rated one of the best on the market. Taking a look at the Powerwall, Tesla’s home battery illustrates why Tesla is such a forward-thinking company.

How the Tesla Powerwall Works

The Powerwall is a home backup battery. Before delving into this battery, however, we need to examine commonly used home battery types.

Lithium Ion Batteries Vs. Lead Acid Batteries

There are two main battery types used for home battery backup. These include lithium-ion and lead-acid batteries.

Lead acid batteries are cheaper. However, there are some pretty obvious reasons why. Lead acid batteries are large and heavy. They also have a lower depth of discharge and shorter lifespan.

This means that although the lead-acid battery is cheaper in the long run, it actually will cost you more. This is why when Tesla created their home battery they made sure it was a lithium-ion battery.

Inner Workings of the Powerwall: a Lithium-Ion Battery Par Excellence

Let’s take a look at the basics of how a lithium-ion battery works. When a battery is powering objects, a current of electrons moves across a circuit. In a lithium-ion battery, this movement is set in motion by the movement of lithium ions across the battery. For reasons beyond the scope of this piece,using a Li-ion battery is the better option.

The Powerwall is a Li-ion battery. Inside the Powerwall, there is a connection point, a liquid-cooling inverter, and a battery pack.

The connection point allows the Powerwall to connect to your home and solar panels. The liquid cooling keeps the battery from overheating. Lastly, the inverter converts direct current in the battery to alternating current for home use.

How Many Powerwalls Needed to Power Your Home

How many Powerwalls you will need depends on how much energy you typically use. It’s also dependent on whether you only want to power essential loads.

Powering Essential Loads

If you determine that you only want to power a couple of things in an outage, one Powerwall will do the trick. The combined power needs of your essentials just need to be less than the continuous power supply of the battery.

Power for the Whole Home

Whole home power refers to the number of batteries you need to power your entire home during an outage. This is still less than the number of batteries you would need to continuously power your home.

Mounting Styles of the Powerwall

When you get your Powerwall(s) there are several different ways you can choose to have them mounted. These include side-by-side, front-to-back and stacking.

Side-by-side mounts are installed along a wall. In order for this mount to work, you need room on each side for electrical connections and ventilation.

Front-to-back mounts are floor mounted using stake kit hardware. For this installation to work, it also needs to be anchored to a wall.
Stacking mounts are installed on the wall. You can stack up to three Powerwalls in one stack.

The Tesla Mobile App

Once you have your Powerwall installed you are ready to use the mobile app. This app not only keeps track of when your powerwall is being used but allows you to control its use.

Home Battery Competitors

Although the Powerwall is the best home battery on the market, it isn’t the only one. To determine which home battery will best meet your needs, there are six categories to compare. These categories include capacity, depth of discharge, round trip efficiency, chemistry and warranty.

Capacity is the amount of usable energy that the battery can hold. The depth of discharge tells you how much of that energy you can use before it needs to be recharged.

Round trip efficiency tells you how much power is being lost each time the battery is recharged. A high charge round trip efficiency is ideal.

The chemistry of the battery as stated earlier can make a difference in the longevity of the battery. Most batteries are either Li-ion or Lead-acid. The last thing to consider is the battery’s warranty; a quality warranty is long-lasting and will protect you against possible issues.

Comparison of the Sonnen Home Battery

Sonnen currently has two home battery options. These include the Sonnen eco and the Sonnen ecoLinx.

Capacity of the Sonnen eco and ecoLinx

The Sonnen eco has 5-15 kilowatt hours of usable capacity.  And the Sonnen ecoLinx’s usable capacity is between 10-20 kilowatt hours.

Sonnen Depth of Discharge for the Eco and EcoLinx

The Sonnen eco has a continuous output of 3,000 – 8,000 watts of alternating current. This is equivalent to 3 to 8 kilowatts. The Sonnen ecoLinx has a continuous output of 8,000 watts of alternating current.

Round Trip Efficiency and Warranty of the Sonnen Home Batteries

The efficiency of the eco and the ecoLinx is 93 percent. However, their cycles and warranties are different. The eco has a 10,000 cycle 10-year warranty and the ecoLinx has a 15,000 cycle 15-year warranty.

Chemistry of the Sonnen Home Batteries

Last of all is the chemistry of the batteries that Sonnen offers. Both of these batteries are Li-ion batteries.

Sonnen ecoLinx 20 Full Specs

  • Weight: 950 lbs
  • Dimensions: (26 in x 83 in x 14 in)
  • AC Voltage (Nominal): 120/240 volts
  • Grid Frequency: 60 Hz
  • Usable Energy: 20 kWh
  • Max Continuous Power: 8 kWh
  • Round Trip Efficiency: 86%
  • Warranty: 15-year or 15,000 cycles

Taking a Look at the LG Chem RESU Home Battery

The LG Chem RESU batteries have gained a lot of traction lately. Let’s take a look at the specs for this battery so you can better determine if this traction has any merit.

There are five different sizes of batteries available. These include RESU3.3, RESU6.5, RESU10, RESU7H and the RESU10H.

Capacity and Depth of Discharge of LG Chem Home Batteries

Depending on the model that is chosen, the LG Chem batteries have a capacity between 3.3 and 9.8-kilowatt hours. However, the depth of discharge is less. For the smallest battery that depth of charge is 2.9-kilowatt hours and the largest battery has a depth of charge of 9.3.

Round-Trip Efficiency Chemistry and Warranty of LG Chem

All of the LG Chem batteries have a 95 percent round trip efficiency and a 10-year 80 percent capacity warranty. They are also all Li-ion batteries.

LG Chem RESU10H Full Specs

  • Weight:214-220 lbs
  • Dimensions: (29.3 in x 35.7 in x 8.1 in)
  • Voltage range: 350-450 V and 385-550 V
  • Total Energy: 9.8 kWh
  • Usable Energy: 9.3 kWh
  • Max Continuous Power: 5 kWh
  • Peak Power: 7 kWh
  • Round Trip Efficiency: 95%
  • Warranty: 80% after 10 years

What Sets the Powerwall Apart From the Competition

Because the Powerwall is a Tesla product, it already has a reputation for quality. However, taking a look for yourself will ensure that this home battery really is the top of the line in terms of what you need.

Capacity  and Depth of Discharge of Tesla Home Batteries

The Tesla Powerwall has a usable capacity of 13.5-kilowatt-hours with a continuous power supply of  5 kilowatts. It also has a depth of discharge of 100 percent. This means that you will get hours from your battery before it needs to be charged.

Round-Trip Efficiency, Chemistry and Warranty of the Powerwall

The Powerwall also has a round-trip efficiency of 90 percent. Their battery is a Li-ion battery with a 10-year warranty. Although it is warrantied for 10 years, depending on how regularly you use it, the battery could last much longer.

Tesla’s Powerwall 2 Full Specs

  • Weight: 276 lbs
  • Dimensions: (45.3 in x 29.7 in x 6.1 in)
  • Mounting Types: Floor and wall mount
  • AC Voltage (Nominal): 120/240 V
  • Internal Battery DC Voltage: 50 V
  • Grid Frequency: 60 Hz
  • Total Energy: 14 kWh
  • Usable Energy: 13.5 kWh
  • Max Continuous Power: 5 kWh
  • Peak Power: 7 kWh
  • Round Trip Efficiency: 90%
  • Warranty: 10-year

Cost Savings of the Tesla Powerwall

How much something costs is one of the most pressing questions that most have. Especially with large purchases such as a home battery. However, what needs to be taken into consideration is how much of that price is going to be made up for in the savings.

Applying the ITC to the Powerwall and Solar

If you purchase a Powerwall 2 with your solar array you can qualify for the Federal Investment Tax Credit (ITC). Currently, this credit covers 30 percent of the cost. This is a huge chunk of the cost so you will want to remember it when you file your taxes the following year.

How the Powerwall Pays for Itself

Even with this discount, purchasing a Powerwall is an investment. However, this is an investment that is well worth the money. When you purchase a Powerwall for your home you are investing in solar storage.

A solar system can generate electricity all day, but as soon as the sun goes down it no longer is able to produce power. Often people make up for this by staying connected to the grid.

However, net metering programs are not always fair in the eyes of customers. Often, utilities pay less for customer solar generation then what they charge for their power.

When you install a Powerwall, you are able to store your excess power for later use. This means you don’t have to worry about losing as much money to the utility. In fact, over time, you will recoup the money you spent on the home battery through savings on electric bills.

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