How long can you run your house on a Tesla Powerwall?

The simple answer: a Tesla Powerwall can run the average home for just over 11 hours.

Truthfully, it’s not that simple. The amount of time your Tesla Powerwall can power your home depends on several factors specific to your home’s energy use and what devices you’re running. For example, the Tesla Powerwall could last more than two days on a single charge if you’re only using essentials like your lights, refrigerator, Wi-Fi, and phone charger.

So while we can’t give you a definitive answer, we’ve outlined steps to calculate how long you can run your home using the Tesla Powerwall battery.

We figured out the Tesla Powerwall can power the average home for about 11 hours and 10 minutes using a simple equation:

• (13.5 kWh / Avg daily home electricity use) x 24 = # of hours your Powerwall will run

For this calculation, we used the U.S. average daily household electricity use of 29 kilowatt-hours (kWh). Since the Tesla Powerwall has an energy capacity of 13.5 kWh, we divide 13.5 by 29, which gives us 0.466 days. Multiply that by 24 hours in a day to get 11.04 hours—or roughly 11 hours and 10 minutes.

• (13.5 kWh / 29 kWh) x 24 = 11.04 hours

You can swap out the 29 with your average daily electricity use for a more personalized answer to how long your Powerwall will run. To find yours, look at your utility bill. If it doesn’t outline your average daily consumption, divide your monthly usage by the number of days in that month. 

For a closer estimate, we’ve calculated how long the Powerwall would run the average home by region, using monthly U.S. Energy Information Administration (EIA) data.

How long the Tesla Powerwall will run your house by region

Not sure which region your state is in? Check out the chart.

Note: The average energy used per day is estimated based on annual averages, but energy use typically fluctuates by season—this will affect how long your Powerwall will last.

If you want a more accurate answer for how long your house can run on a Powerwall, you need to know:

• How much power you need for your devices

• How that compares to how much power the battery can provide

The power in batteries like the Powerwall is measured in kilowatts (kW), while our appliances are typically measured in watts (W). Luckily, it’s easy to convert; just divide the watts by 1,000. Example: A 350 W refrigerator uses 0.35 kW. 

Let’s break it down further:

To calculate how much power your home needs

You’ll first need to decide which devices you want your Powerwall to power; then, you’ll calculate how much energy those devices use.

If you don’t have the wattage of each appliance readily available, we highly recommend a quick read of our article on understanding electrical loads, which walks you through calculating the electrical load for various appliances.

Next, consider how long you want to run your device for. Your refrigerator or Wi-Fi likely stay on, but you probably won't use things like your phone charger or your TV for more than a couple of hours.

Finally, convert your appliance’s wattage into kilowatts by dividing 1,000; then, multiply the kilowatts by the number of hours you expect the device to run.

• Energy (kWh) = Power (kW) × # of hours

The chart below outlines how much electricity some common household appliances use when running for one hour and 12 hours.

*A device’s listed wattage is usually higher than how much power it actually needs to run because most appliances cycle on and off. For example, a refrigerator cycles on and off throughout the day, so a 500-watt refrigerator actually only uses about 167 watts. (You can divide your refrigerator’s wattage by 3 to estimate its actual energy usage.) 

For the sake of simplicity, with the exception of refrigerators, we decided to stick to the device’s listed wattage for our calculations, but your devices will generally use less electricity. So the bottom line is: The Powerwall will probably be able to power your devices slightly longer than what’s listed above.

To calculate how much power the Powerwall provides

All Powerwall models have a 13.5 kWh energy capacity, but this isn’t the only number we need to pay attention to. Home batteries have two other key metrics: peak power and continuous power.

Peak (instantaneous) power is the amount it takes to start an appliance: In our fridge example, the appliance may need 500 W (0.5 kW) when first plugged in, but the energy required to keep it running is lower. If your appliances have a “surge” requirement, the battery’s peak power will need to be enough to cover that

Continuous power is the maximum amount of power that the battery can supply at any given moment; for example, the power needed to keep the 500 W fridge up and running after it’s started is typically around 167 W or 0.167 kW. This will tell you how many appliances you can continue to run over time, say an hour or more.

The screenshot below compares the peak and continuous power ratings of the three Tesla Powerwall models currently on the market.

Screenshot from Tesla.com.

We can see Tesla Powerwall 3 has a continuous power output of 11.5 kW, which means the battery can continuously run appliances that draw less than 11.5 kW of power for as long as the battery has energy. (If you have a Powerwall+, the continuous power output is reduced to 7.6 kW, and so on.)

The continuous power rating for home batteries typically ranges from 5 to 8 kW, so the Tesla Powerwall 3 really stands out with its 11.5 kW power rating.

To answer the “how long” question, you’ll compare the two factors: the usable storage capacity and how long you're using each appliance.

Energy (usable storage) capacity

Energy capacity—or the fancier term “usable storage capacity”—tells us how much electricity the battery stores. The energy capacity is listed in kWh because it represents using a certain amount of electricity (kW) over a certain amount of time (hours).

The usable storage capacity for a single Tesla Powerwall is 13.5 kWh. Functionally, this means you can use either 13.5 kW for 1 hour, 1 kW for 13.5 hours, or something in between.

Appliance run time

Now that we know roughly how much power our appliances draw, let's determine how long the Powerwall can power each device. We'll take that 13.5 kWh of energy capacity and plug it into the following equation:

• (13.5 kWh / avg electricity use) = # of hours your Powerwall will run it

The big thing to remember here is that you'll probably be running a few of these at any given time, which changes the number of hours the Powerwall will last. For example, if you're running the refrigerator and you want to turn on the TV, this will eat into the amount of time you'll be able to run the refrigerator.

If there was a power outage and you couldn’t recharge your Powerwall, you’d probably reduce your appliance use to a few essentials to extend the length of your battery. For example, your Powerwall could power your refrigerator, phone charger, Wi-Fi router, and a few lights for roughly 59 hours and 21 minutes (2 and a half days) on a full charge.

This is the last important question in the equation. Up until this point, we’ve calculated how long a standalone Tesla Powerwall would last on a single charge. But if you have a solar panel system, you can charge your battery almost indefinitely—even during a blackout if the sun is shining.

If you still don't think one Powerwall will give you enough power, it's important to understand how to expand your system. Many households get at least two Powerwalls to meet their energy needs. Tesla has made it pretty easy by adding the option for the Powerwall 3 Expansion to extend backup energy capacity by an additional 13.5 kWh without paying full price for another battery. (As the name implies, it can only be added to the Powerwall 3.)

For more guidance on how many Powerwalls you should get to meet your energy needs, talk with one of our free Energy Advisors when you get quotes through the EnergySage Marketplace.