When the power goes out, you may wonder how long a Tesla Powerwall can keep your home running.
The answer depends on how much electricity your home uses, what you’re running during the outage, how many Powerwalls you have, and whether your system is connected to solar.
A Tesla Powerwall 3 stores 13.5 kWh of energy and can provide up to 11.5 kW of continuous power. But that doesn’t mean every home will get the same amount of backup time. A home using only essential appliances will use its stored energy much more slowly than one running air conditioning, an electric water heater, an EV charger, and other large loads.
How Long Will a Tesla Powerwall Last During a Power Outage?
There isn’t one number that applies to every home.
A Powerwall’s backup time depends on:
- How much electricity your home uses
- Which appliances are running
- How many Powerwalls you have
- Whether solar can recharge the battery
- Whether you’re backing up the entire home or only essential loads
For a simple example, a Powerwall 3 stores 13.5 kWh.
If your home averages 1 kW of electricity use, that stored energy would theoretically last about 13.5 hours. At an average of 0.5 kW, it could last roughly 27 hours. At 2 kW, it would be closer to 6.75 hours.
These are simplified examples. Your home’s energy use changes throughout the day, so actual backup time will vary.
What Uses the Most Power During an Outage?
Some appliances use considerably more electricity than others.
Large energy users can include:
- Central air conditioning
- Electric heating
- Electric water heaters
- Electric dryers
- Electric cooking appliances
- Pool pumps
- Well pumps
- EV chargers
Smaller loads such as refrigerators, lights, Wi-Fi, and phone chargers generally require much less energy.
If you’re trying to stretch your backup time, limiting high-energy appliances can make a significant difference. Tesla recommends reducing energy-intensive loads during an outage to help conserve Powerwall energy.
Can a Powerwall Run Essential Appliances?
Yes. A Powerwall can back up common household loads, including refrigerators, lights, Wi-Fi routers, televisions, and other appliances. The exact appliances you can run depend on how your system is configured. Some homeowners choose to prioritize essential loads during an outage rather than trying to run everything as they normally would.
For example, you might keep your refrigerator, lights, Wi-Fi, and essential outlets running while turning off an EV charger, pool pump, or other high-energy equipment.
What If You Have Solar Panels?
Solar can make a big difference during a longer outage. When Powerwall is connected to solar, your panels can continue producing electricity during an outage and can recharge the battery when conditions allow.
For example, if an outage starts overnight, the Powerwall can provide backup power while your solar panels aren’t producing. Once the sun comes up, your solar system can produce electricity for your home and recharge the battery with excess energy.
That means you’re not limited to the energy stored in the battery when the outage begins. Solar production can vary, though. Cloud cover, storms, shade, and other conditions can reduce how much energy your panels produce.
How Many Powerwalls Do You Need?
One Powerwall isn’t necessarily the right amount of storage for every home.
A larger home or a home with higher electricity use may need additional battery capacity, especially if you want to run larger appliances during an outage. Powerwall 3 has 13.5 kWh of energy capacity, and additional Powerwall 3 units can increase the total available storage.
The number you need isn’t determined by square footage alone. Your installer should look at your electricity use, the appliances you want backed up, and how much backup coverage you’re looking for.
How Can You Make a Powerwall Last Longer?
If you’re dealing with a long outage, a few simple changes can help stretch your stored energy.
Limit High-Energy Appliances
Avoid running several large appliances at the same time. If you don’t need something during the outage, turn it off.
Prioritize Essential Loads
Focus your available energy on the appliances and equipment you actually need, such as your refrigerator, lights, Wi-Fi, and essential outlets.
Monitor Your Energy Use
The Tesla app allows Powerwall owners to monitor their system during an outage. If your battery is getting low, reducing your home’s energy use can help extend the remaining backup time.
Let Solar Recharge the Battery
If you have solar and weather conditions allow your panels to produce enough electricity, your system can recharge the Powerwall during the day. This can be especially helpful during outages that last multiple days.
What Happens If the Powerwall Runs Out?
If the Powerwall’s stored energy gets very low, it can stop providing power to the home.
Tesla states that Powerwall enters a standby state when it reaches less than 10% energy remaining. If it’s connected to solar, it can attempt to recharge once enough solar energy is available.
Reducing your home’s energy use while the battery is low can help conserve the remaining energy.
So, How Long Will Your Powerwall Last?
The answer depends less on a fixed number of hours and more on how your home uses electricity.
A Powerwall can provide significantly different backup times depending on whether you’re running only essential appliances or trying to power your entire home as normal. Solar and additional battery capacity can extend that coverage even further. That’s why battery sizing should be based on your home’s actual energy use and what you want to keep running when the grid goes down.
Want Backup Power for Your Home?
If you’re considering a Tesla Powerwall, 8MSolar can help you look at your home’s energy use, solar production, and backup goals to determine what type of battery setup makes sense.