Tech & Energy
Battery Backup Autonomy Calculator
How long does a Powerwall really last when the grid is down? Depends on what you keep running.
Days of backup
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- Usable kWh
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- Hours of load
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- With solar (indefinite if net positive)
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FAQ
What is a critical load? +
Fridge, lights, internet, phone charging, well pump, furnace blower (not heat strips). Strip out AC, EV charging, hot tubs for backup.
Why reserve %? +
Lithium batteries last longer if you do not fully drain them. 20% reserve doubles cycle life.