Home Solar Battery Recharge Window

Know exactly how long your home battery needs to recover after a deep discharge. Enter the battery capacity, inverter charge rate, and any simultaneous PV production to see the hours required to reach full charge and how quickly you can bounce back to a resilient state-of-charge.

Use the installed capacity listed for your Powerwall, Enphase IQ, LG RESU, etc.
Maximum continuous power from the inverter or backup gateway dedicated to charging.
Defaults to 80% usable energy so 20% state-of-charge remains in reserve.
Defaults to 90% to reflect inverter and wiring losses.
Optional PV output available during daylight to supplement the charger.

Consult your installer or manufacturer for exact charging profiles before adjusting system settings.

Examples

  • 13.5 kWh battery, 5 kW charger, 80% DoD, 90% efficiency, 2.5 kW solar ⇒ Energy to restore (80% DoD): 10.80 kWh • Effective charging power: 7.50 kW • Time to full recharge: 1.44 hours (86.67 minutes) • Approximate time to reach 90% state-of-charge: 1.30 hours
  • 20 kWh battery, 3.8 kW charger, DoD blank, efficiency blank, solar blank ⇒ Energy to restore (80% DoD): 16.00 kWh • Effective charging power: 3.80 kW • Time to full recharge: 4.67 hours (280.00 minutes) • Approximate time to reach 90% state-of-charge: 4.20 hours

FAQ

Can I include generator charging?

Yes. Add the generator output (minus loads it must support) to the charging power field so the calculator reflects combined charging sources.

What if I only charge off-peak overnight?

Set the solar assist to zero and use your off-peak inverter charge limit. The resulting hours show how long you need to schedule the charge window.

Does the tool model tapering at high state-of-charge?

It assumes constant power charging. Lithium-ion systems often taper near full, so treat the result as a best-case window and add a buffer for the taper zone.

How do I plan for multiple batteries?

Multiply the nameplate capacity and available charge power by the number of batteries, or run the calculation once and scale the result based on how many packs charge in parallel.

Additional Information

  • Depth-of-discharge reflects how much of the battery you actually used—most home systems keep a reserve to protect cell health.
  • Round-trip efficiency captures inverter and wiring losses; high ambient temperatures or older batteries can reduce efficiency.
  • Solar assist should use realistic daytime production during outage recovery, not STC nameplate ratings.

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