The Powerwall is a rechargeable lithium-ion battery stationary energy storage product manufactured by Tesla, Inc.
The Powerwall is intended to be used for home energy storage and stores electricity for solar self-consumption, time of use load shifting, backup power, and off-the-grid use.
How much power can Powerwall 2 supply in a blackout and for how long?
The rate at which Powerwall will discharge power to meet loads is limited to a constant output of 5kW and a short burst of 7kW. So while operating in backup modes you cannot use electrical appliances with a combined draw of more than 5kW, which is just over 20 amps on a 240V.
The length of time for which it can run these loads depends on how much energy was stored in the battery when the grid failed and how much power you use.
If the battery was fully charged when the power failed, and your house uses approximately 2kWh per hour then it could run your house for almost 7 hours.
To provide for greater longevity of power supply for critical appliances in a blackout some consumers who buy Powerwall only wire the system to backup specific loads, such as their refrigerator such that these important appliances will last longer if the grid is down for a long time.
If a Powerwall was only running a refrigerator and some lights it could possibly last for days.
How much energy can the Powerwall 2 store?
The Powerwall 2 can store 14kWh of energy.
Given the average US home uses around 28kWh per day this is quite a reasonable amount of storage to deal with a lot of the night time electricity use of a typical house