How Many Powerwalls Do I Need?

Tesla is one of the most influential companies globally for green energy. From Tesla cars, the Tesla solar roof, to the Tesla Powerwall, they offer complete solar solutions with energy backups and electric vehicles, all combined into one synchronized system.

This article will help you understand how many Powerwalls you need for your home and how a Powerwall can help you become energy independent.

Tampa FLUSA A Tesla Battery Powerwall at the Tesla dealership in Tampa FL. Tesla Inc. is an American automotive and energy company that specializes in electric car and solar panels.

How Many Powerwalls Can You Have?

Strictly speaking, the limit to how many Powerwalls you can have attached to your home or business is ten. But realistically, it depends on the total power draw of your home and how long you need backup power for. 

Most homes may only need the power to last 24 hours after a power grid outage. If you have a Tesla vehicle charge your vehicle at home, you could invest in additional Powerwalls for more capacity.

How Many Powerwalls Should a House Have?

Most homes can get by with a single Powerwall, but it all depends on the power draw of your house. It’s vital to calculate the power draw of your home by adding up all appliances that are constantly on, like a refrigerator. 

Add in items that you do not always use, but draw a lot of power when in operation, such as air conditioners or heaters (not to mention charging your Tesla vehicle). When you know your home’s load, you can reliably calculate how many Powerwalls you’ll need.

Here’s an example of the power that a home needs for domestic appliances.

Appliance TypeStartup WattageRunning WattageWattage Difference
Electric Water Heater4500 W4500 W0 W
2 Ton Air Conditioning8750 W3800 W4950 W
Fridge / Freezer2900 W700 W2200 W
Clothes Dryer6750 W5400 W1350 W
Washing Machine1200 W1200 W0 W
Cool / Dry Dishwasher540 W216 W324 W
TVs (2)380 W380 W0 W
Lighting (LED)1000 W1000 W0 W
800W Microwave1300 W1300 W0 W
Laptop / Wifi300 W300 W0 W
Electrical (Various)2000 W2000 W0 W
Totals29620 W20796 W10174 W
Power in Watts Required For Domestic Appliances

The basic Tesla and Powerwall system is 10 solar panels and a Powerwall. With this system in ideal conditions, you will generate 13.5 kWh per day and a Powerwall can hold 12.2 kWh.

Based on those calculations, to run a house with a Tesla Powerwall and Tesla solar panels, you’ll need one Powerwall and 22 solar panels to run a typical American home.

This calculation is for peak conditions, which will be in hot southern climates in the summer. So to be sure that you’re constantly powered, it’s best to calculate your minimum needs and winter conditions for your area.

See also: Tesla Solar Panel Review (Specs – Is It Worth It?)

Do I Need One Powerwall or Two?

For a small grid-connected home, maybe you can get by with one Powerwall if you don’t need backup power for a long time and you don’t have many power-consuming devices. 

If you’re not sure what you’ll need, it’s okay to start with only one Powerwall and expand to two or more if you need them. They are designed to allow for later additions.

For off-grid installations, I recommend at least two Powerwalls, though more may be necessary. Two Powerwalls can store 24.4 kWh, which will be enough to supply you with power for a day.

How Many Powerwalls Do I Need to Be Off the Grid?

For an average-sized home, consider at least two Powerwalls as a completely off-grid solution. You might need more depending on your location and needs. 

Many factors are consequential for calculating whether an off-grid solution is possible, such as the number of sun hours per day, average high and low temperatures throughout the year, size of the home, amount of electrical load from appliances within the property, and electric vehicles.

A solar photovoltaic (PV) system is used with off-grid Powerwalls, but you could include wind, geothermal, or even biomass generators to create a complete system. 

Up North

For colder northern climates, you may need a larger than average solar array to charge up Powerwalls fully to provide heat. 

Down South

In a sunny desert climate like Arizona, a smaller solar array may be sufficient because of the abundant sunshine. But you also need more power for air conditioning. The number of Powerwalls necessary to go completely off-grid is a complicated question with many variables. 

Using the Tesla Powerwall smartphone app, it is possible to simulate an extended outage and discover how much capability your Powerwalls can handle in an extended emergency.

How Long Will A Single Powerwall Last?

Some homes can get by with a single Powerwall. The capacity of a single Powerwall is about 13 kilowatts, so depending on the power draw of the house, one Powerwall can power a non-solar home without the grid for about 13 hours. 

That’s assuming your home draws 1 kilowatt per hour, which is the average. That may not be enough for your home, depending on where you live and whatever natural threats you face.

Are Powerwalls Worth the Investment?

Consider a Powerwall as insurance against loss of energy supply from the grid. You hope you never need it, but if you do, you’ll be glad you have it. 

Think Bigger – Powerwall Scalability

Tesla built the Powerwall system with scalability in mind. If you have a house that can function for a few hours with only one Powerwall and that’s all you need. A single Powerwall may suffice. You can always add more later if your needs change.

Reason With Me: Backup or No Backup?

But what if you are running a business with facilities that require a lot of power? 

  • Do you run web servers for an e-commerce business that always have to be on? 
  • Do you need a 24-hour security system? 
  • Maybe you own an ice cream shop. 
  • What if it lost power and all of your product melted because of no backup power? 

There are a million reasons to justify the investment of an adequate power backup solution, but there is no reason I can think of not to have it.

Benefits Of A Tesla Powerwall

Another advantage of Powerwall is its ability to charge when your grid’s rates are lowest and save that power to be used later when the rates are the highest. Essentially, you can choose when you buy your power and when to use it to get the best rates. Over time, it can pay for itself.

If your home already has solar and you want to add battery backup, Powerwall+ is for you. It can charge from the grid or from solar. During the day, solar will power your home with the excess going to the Powerwall+ as a backup. 

At night, Powerwall+ can power your home (if there is no grid) until the morning when the sun charges it up again.

What Are The Tesla Powerwall Products?

Battery Storage System

The Tesla Powerwall is a battery storage system for single-family homes and businesses. It can primarily serve as a backup power reserve when your local power grid goes down because of storms or other problems. 

Combi – Add Solar Panels

Combined with a PhotoVoltaic (PV) solar panel installation, a home can function completely off-grid. If you have a Tesla electric vehicle, it’s possible to power your car from the sun! Energy doesn’t get any cleaner and greener than that.

Powerwall and Powerwall +

Tesla Powerwall is available in two varieties: 

  • Powerwall and 
  • Powerwall+. 

They are mostly identical except for how they handle solar power and how much continuous power they can supply. 

They both have a battery storage capacity of 13.5 kWh (kilowatt-hours) but the Powerwall+ can supply more energy over time (up to 7.6 kVA [kilovolt-ampere] with solar power and full sun).

Note the differences between the original Powerwall (no longer manufactured) and the Powerwall 2 (commonly known as Powerwall today). 

The first Powerwall capacity was only 6.4 kWh of storage compared to the vastly improved 13.5 kWh capacity of the Powerwall 2. For simplicity, I will refer to Powerwall 2 as Powerwall throughout this piece.

Energy Supply and Peak

Powerwall is a standard backup solution for a non-solar-powered home. But only your local electrical grid charges it. When the grid goes down, Powerwall supplies 5.8 kW of continuous power or a 10 kW peak. 

If you want to add solar to your home later, Powerwall is compatible with all third-party grid-tied solar inverters.

Tesla Powerwall FAQ

Can Powerwalls Go Outside?

Yes. You can install Powerwalls outdoors or indoors. But consider the climate where you live. Heat, cold, humidity, etc., can affect their performance. 

Batteries are less efficient in colder climates. They designed the Powerwall chassis to be fireproof and to contain any internal battery fires because of thermal runaway. 

Can I Make a Tesla Powerwall Last Longer?

If a home’s local power grid is unavailable due to a disaster, a single Powerwall can last between 12 to 15 hours, assuming a maximum 2 kWh draw. 

If this means I have to make some sacrifices by turning off high-draw appliances such as air conditioning, I can extend the time I go in low-power mode. 

Can Powerwall Charge a Tesla Car?

Yes! Tesla designed Powerwall products to work together to create a total solution for your home and vehicle. 

With a Tesla Solar Roof, Powerwalls, and a Tesla vehicle, your home can charge your car powered with solar energy.

The only caveat to that scenario is whatever energy I divert to charge my car is energy not available to power my home. Home and car share the same Powerwall resources. 

So if you have a Tesla (or any other electric vehicle) and you want or need Powerwalls as a backup, factor in enough capacity to serve both.

How Much Does a Tesla Powerwall Cost?

A single Powerwall unit costs $7500 without the installation. A Powerwall + with an integrated solar inverter necessary for solar PV systems comes to $8500 each, but without solar panels.

Consider also energy incentives when combining your system with solar technology, which will set off some of the cost of your investment.

Into the Future – Powerwall 3

Tesla’s announced its latest and greatest Powerwall, the Powerwall 3, to be released no earlier than Spring 2022. It will have a 9.6 kW peak output (increased from 7 kW) and the same 13.5 kW battery capacity. 

That means more power is available for your home for the same duration or you can draw higher output.


Photo of author
Elliot has 20+ years of experience in renewable technology, from conservation to efficient living. His passion is to help others achieve independent off-grid living.

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