Power Planning Calculator

Battery Runtime Calculator

Estimate how long a portable power station or home battery can actually run your devices.

Read: Battery Runtime Explained →

Estimated runtime

7hrs15m

A 1024Wh battery at 85% powering a 120W load.

Your Setup

Fill in your battery and load. Results update instantly.

1Battery capacity

Found on the label or specification sheet of your power station or battery.

2Usable capacity

Inverters lose energy as heat. Typical (85%) is a safe default.

3Device load

watts

Combined running wattage of everything you plan to power at once.

Estimated runtime

Solid match

7hours15 min· Based on 870Wh of usable capacity powering a 120W load.

Runtime range6.4-7.7 hrs

0htypical8.8h

Rated capacity1024 Wh

Usable capacity870 Wh

Power draw120 W

Battery used per hour11.7%

Want longer runtime?

Reduce the load

Add an expansion battery

Recharge from solar

Recharge from a generator

What You Need to Know

Watts vs. watt-hours: Watts measure how fast energy is used. Watt-hours measure how much energy is stored.
Efficiency losses: Inverters commonly lose 10-25% of stored battery energy as heat.
Cold weather: Lithium batteries usually deliver less usable energy in freezing temperatures.

Rule of thumb
Runtime equals usable battery capacity divided by device load.

HOME POWER MATRIX

Power Planning Report

Battery Runtime Calculator

Your Runtime Estimate

Estimated runtime

0 hours 0 min

Expected range-

Setup rating-

Your Inputs

Battery entered-

Rated capacity-

Usable capacity setting-

Calculated usable capacity-

Load entry mode-

Total power draw-

Device Load

Device	Watts each	Qty.	Subtotal
Combined load			-

Assessment

How This Estimate Works

FormulaRuntime equals usable battery capacity divided by the combined device load.

Real-world rangeThe range compares conservative 75% efficiency with optimistic 90% efficiency.

Plan for variationCold weather, battery age, inverter losses, startup surges, and changing device loads can reduce actual runtime.