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Home Solar Battery Backup Runtime (Powerwall) Calculator

Calculate whole-home and critical-load battery backup runtime in blackout hours based on battery capacity (kWh), depth of discharge (DoD), and household appliance wattage.

Laptops, CPAP machine, TV, device chargers

Calculation Results

Blackout Backup Runtime: 15.0 Hours (No Solar) With 12 kWh Daily Solar: Indefinite Off-Grid Operation!
Average Total Load Draw: 900 Watts
Daily Energy Consumption: 21.6 kWh / 24 hrs
Backup Strategy Rating: Critical Circuits Sustained

About This Calculator

Calculate whole-home and critical-load battery backup runtime in blackout hours based on battery capacity (kWh), depth of discharge (DoD), and household appliance wattage.

Frequently Asked Questions

How long does a Tesla Powerwall (13.5 kWh) last during a power outage?

Powering essential loads (refrigerator, LED lights, Wi-Fi, phone chargers averaging 500 Watts), a single 13.5 kWh Powerwall lasts approximately 24 to 28 hours. If paired with rooftop solar panels that recharge the battery during daylight, backup runtime can continue indefinitely.

Can a single battery run a whole-house central air conditioner?

A central 3-ton to 5-ton air conditioner draws 3,000 to 5,000 Watts continuously and requires a massive starting surge current (LRA) of 60 to 100 Amps. A single battery will drain in 2 to 3 hours unless equipped with a soft starter or backed by two or more batteries.

What is Depth of Discharge (DoD) in modern lithium home batteries?

Modern Lithium Iron Phosphate (LiFePO4) and NMC batteries (like Tesla Powerwall 3 and Enphase) offer 100% usable Depth of Discharge, meaning you can utilize all advertised kWh without damaging the battery chemistry.

What is the round-trip efficiency of a home battery system?

AC-coupled home batteries typically operate with an 89% to 92% round-trip efficiency due to DC-to-AC and AC-to-DC conversion losses in the hybrid inverter.