Run time is the usable stored energy divided by the load. Running only essential circuits stretches it a long way.
How it works
Hours = usable kWh × (1 − reserve) ÷ load in kW.
Example: 13.5 kWh running 1.2 kW lasts about 11.2 hours.
At a glance
Same settings as the calculator, changing only the load.
| Load | Run time |
|---|---|
| 0.5 kW | 27.0 hours |
| 1 kW | 13.5 hours |
| 1.5 kW | 9.0 hours |
| 2 kW | 6.8 hours |
| 3 kW | 4.5 hours |
| 5 kW | 2.7 hours |
Tesla Powerwall 3 at a glance
| Usable energy | 13.5 kWh |
|---|---|
| Continuous power | 11.5 kW |
| Off-grid continuous power with solar | up to 15.4 kW |
| Charging power | 5 kW |
| Average installed cost (13.5 kWh battery, EnergySage, H1 2026) | $15,647 |
Common questions
How long will a Powerwall last in an outage?
13.5 kWh runs a 1 kW load for 13.5 hours. With solar recharging during the day it can last much longer.
What uses the most battery?
Central air conditioning, electric heat, water heaters, ovens and EV charging. Leaving them off stretches backup time.
Sources
- Tesla, Powerwall 3 specifications: https://service.tesla.com/docs/Public/Energy/Powerwall/Powerwall-3-with-Gateway-3-Installation-Manual-NA-EN/GUID-EC527BC7-4750-4425-BBC4-DB8C000339B3.html