How to Calculate the Number of Powerwalls You Need

How to Calculate the Number of Powerwalls You Need

When you cannot rely on your home’s generator to withstand blackouts during harsh weather or emergencies, you can invest in a Tesla Powerwall in order to keep your home powered up. However, you need to have the correct amount of Powerwalls if you want to successfully power your home. You do not need formal education or training in energy usage in order to determine how many Powerwalls will be sufficient for you.

In order to calculate how many Powerwalls you need to power your home, you must understand how much energy your home uses and determine what energy you will need on standby if your power goes out. Read on to learn how to calculate the number of Powerwalls you need to power your house in a blackout.

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Understand Energy Usage

The first step in calculating the number of Powerwalls you need for your home is determining how much energy you are currently consuming. Your energy usage likely changes from year to year based on multiple factors. Some of these can include:

  • New electric vehicles
  • Severe, uncharacteristic weather
  • Working from home

Looking at the monthly usage bar graph on your energy bill might cause more stress than help. Focus on the kWh symbol, which determines the energy you consume in kilowatt-hours over a certain period of time.

If you remember from math, science, or Greek, the word kilo means a thousand, so a Kilowatt is 1,000 watts. The average home in the United States uses 916 kWh per month or 30 kWh per day. However, any of the factors above can cause you to use much more than that in one month.

Calculate the Energy You Use

Every state, and sometimes specific counties, has different ways to report how much energy you use per month.

  • Your monthly electric bill should clearly list your usage by kWh.
  • You can also call your electric company for a more personal overview.

Once you know the average total amount of energy you use in a month, you will need to look at the energy consumption of your home appliances. Write down how much energy each appliance draws. You can find this information on the appliance labels, manuals, or online.

Add up the total amount for each appliance you use. This will give you a general idea of how many kilowatts you need if the power goes out. This is important because each Powerwall has a capacity limit, and you want to know how much energy you would need, so you do not overload your Powerwall.

Determine What You Need If the Power Goes Out

Once you have calculated the number of kWh you use per month, you can then figure out how much energy you would use in one day. This will then help you determine how much energy you need during a power outage. If your household’s average energy consumption is 1,000 kWh, then on average, you would need 33 kWh per day.

However, during an outage, it is reasonable to say that you will not need to watch television, play video games for hours, or run the ice maker. You could reasonably get by on less than 33 kWh per day if you are trying to just stay warm or keep the lights on in the house.

After figuring the kWh you would need per day, it is up to you to decide how many days you think you will be out of power and need a backup power source. It might be a good idea to calculate the energy you would need in the different scenarios you have been through before to come up with a realistic kWh you would need.

Below are a few very different scenarios regarding power needs during an outage.

  • Rarely need energy backup
  • Require power for normal yearly outages
  • Staying on the safe side
  • Living a normal life during an outage
  • Never wanting to go without power

Each of these scenarios could require different numbers of Powerwalls since one Powerwall can only store and provide so much backup energy.

Rarely Need Energy Backup

Tesla’s solar-powered Powerwall units provide energy, so you do not have to rely on your energy company to provide you power. This is called off-grid power. But, these Powerwalls are a great alternative to generators during outages since they also store excess solar energy. They provide energy during outages or even at night.

  • If you live in an area that rarely sees extreme or turbulent weather, your home may need just a few hours over a couple of days of power.
  • If your Powerwall can charge using solar during the day, you may not need much.

If you are using minimal energy, you could reasonably use a 4.08 Powerwall system, which produces 16 to 21 kWh.

Even if you purchase the basic Powerwall unit, a Tesla representative will need to help you with the permitting and installation. Tesla uses aerial images of your home to determine where the Powerwall and solar panels can best be installed, install the units and monitor your energy usage.

Require Power for Normal Yearly Outages

Sometimes, an electric company turns off power for a few hours one day of the year for testing. It is also possible for the power to be out for a day or two during the winter.

  • In this average situation, where you know you will be okay, although cold or uncomfortable, you can minimize energy usage.
  • If this is the case, you may be okay with partial blackouts.

In these typical situations, an 8.16 Powerwall system, which produces 32 to 41 kWh, would work well.

If you cut back energy usage in these normal situations, this Powerwall unit should meet the average daily energy consumption of 33 kWh.

Staying on the Safe Side

Some areas experience more power outages due to more extreme weather or even having the energy companies themselves pushed to their capacities. There are also homes that are larger, requiring more energy or more people in the house to consider during an outage.

A 12.24 Powerwall system, which gives out 48 to 62 kWh, is a good fit for these situations and households that need consistent daily power during an outage.

This amount of energy is above the average amount of energy usage and should provide enough daily energy, especially if it is recharged during the day with solar.

If you are an “on the safe-side” type of person, you will want to monitor your Powerwall usage through Tesla’s monitoring system after installation is complete. Monitoring your Powerwall will give you a better understanding of what you are using and may need in the future. This is a phone application that is easy to install and use.

Living a Normal Life During an Outage

If you experience long outages, max out your energy, or just want the safe feeling that everything is running as normal in emergency situations, you will need more power. The 16.32 Powerwall system produces between 65 and 82 kWh and should be able to provide far more than the average American household use for power during the day.

Again, run through the different scenarios where you would need backup power and how long you can go without power. Do not compare yourself with the average energy consumption. After looking at your energy consumption levels and understanding your personal preferences, only you can determine what amount of energy you require.

Never Wanting to Go Without Power

Discussed above are the amounts of energy and the Powerwall models you need during intermittent power outages, but what if you want Powerwalls to power your home full-time? Powerwalls can be used for full-time, off-grid energy.

If you are looking to purchase Powerwalls as a replacement to your energy company, the Tesla website has a calculator which takes your average energy consumption and address and makes a quick suggestion on the number of solar panels and Powerwalls you would need.

One of the biggest problems with this calculation is that Tesla does not service all areas and, therefore, cannot calculate certain addresses.

If you meet the calculation requirements on the Tesla website, you will need to agree to be contacted by a Tesla representative to go over your home design specifics and help you calculate exactly how many Powerwalls you need to provide your house full-time energy off-grid.

Here’s a Helpful Solar Panel Needs Calculator

In order to offset 100% of your electric bill, you will need:

400 Watt Panels

Based on Tesla Solar Panel pricing it will cost:


Does Tesla Offer Discounts on Solar?

Tesla solar panels are already the lowest price solar panels on the market, but are there any other ways to save money when ordering?

In short, the only way to get a discount on Tesla solar panels is by using an existing Tesla owners “referral link” when ordering your Tesla solar panels.

Tesla has did this same “referral program” concept with it’s vehicles and essentially it allows new customers to get a discount on their purchase by using an existing customers personal referral link.

In regards to Tesla solar discounts, using a Tesla referral link when ordering will save you $300 off solar panels or $500 off solar roof.

The referral discounts are typically only available for a limited time before Tesla stops offering the discount, so take advantage of the savings while you can.

tesla solar panel discount

Solar Discounts:


The articles here on are created by Greg, a Tesla vehicle and Tesla solar expert with nearly half a decade of hands-on experience. The information on this site is fact-checked and tested in-person to ensure the best possible level of accuracy.

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