Portable Power Station Runtime & Capacity Calculator

Start with a plan between charges

A fridge overnight, evening lights and a laptop create a different load at different times.
This portable power station runtime and capacity calculator adds those usage windows, then compares two products using their storage, output, efficiency and quotes.
It separates an energy shortfall from an output limitation and an over-budget purchase so you can see what needs to change.

The calculation covers appliances connected to a portable power station through its AC outlets.
It does not estimate phone power-bank charge counts or vehicle starter-battery life.
Starting values are fictional examples, not current product prices or guaranteed performance.
Both language versions use the same calculation; quotes are in KRW, so convert foreign prices consistently before entering them.

Read Wh, running W and startup W separately

Find storage Wh, continuous AC output and surge AC output in the exact model manual.
Do not put an advertised maximum output number into the capacity field.
A voltage-reducing boost feature is not automatically the same specification as surge output; confirm the applicable rating before entering it.

Enter appliance windows and simultaneous use

1. The total plan is the elapsed time until the next charge.
   For a 12-hour plan, time starts at 0 and ends at 12; these fields are not clock times.
   One plan can cover up to 168 hours, and schedules do not automatically repeat the next day.
   
2. Each row contains a device name, quantity and running and startup watts per device.
   Split different appliances, or separate operating windows, into separate rows.
   Enter 0 for an unknown startup value; the corresponding output check will remain unknown.
   
3. Start plus duration must fit inside the total plan.
   Lights starting 8 hours after departure and running for 4 hours use start 8 and duration 4.
   A disabled row, zero duration or zero duty cycle contributes no energy or output requirement.
   
4. Duty cycle is the proportion of a window during which the appliance consumes its running power.
   For a fictional 60W fridge operating for half of a 12-hour window, enter 50%.
   Do not enter an already averaged low power and then reduce it again with duty cycle; that understates energy.
   

Quantity multiplies energy, running watts and startup watts.
All devices within one row share the same window, so use separate rows when two appliances alternate.
Names appear in the saved report; use recognizable model or adapter names to make later checks easier.
If you only know measured average power, use 100% duty for energy and separately verify the actual maximum running watts before relying on the output comparison.

Efficiency, idle draw and reserve are distinct

Required capacity and runtime formulas

Percentages are fractions in these formulas: 80% becomes 0.8.
Required nameplate capacity is rounded upward for display, while sufficiency checks use unrounded values.
Different product efficiencies and idle draw produce different required capacities for the same appliance plan.
Idle watts are already measured on the battery side and are not divided by efficiency again.

The model divides the schedule at every appliance start and end, then accumulates battery demand interval by interval.
Within the interval that would use the reserve, it divides the remaining available energy by that interval’s average battery draw.
If the whole plan fits, the display says at least the entered duration, such as 12 hours, without extrapolating an unentered future schedule.
Meeting demand exactly at the end counts as completing the plan.

Worked example: a 12-hour camping plan

Assume one fictional 60W fridge at 50% duty for 12 hours, two 20W lights for 4 hours starting at hour 8, and one 60W laptop adapter for 2 hours starting at hour 2.
Their energy totals are 360Wh, 160Wh and 120Wh: 640Wh altogether.
With 300W startup for the fridge and startup equal to running power for the other devices, peak running output is 120W and the simultaneous startup envelope is 360W.

A’s runtime differs from a simple whole-plan average calculation.
Only the fridge runs during hours 0–2 and 4–8; the laptop adds load during hours 2–4, and lights add load during hours 8–12.
Moving a heavy load earlier can change the time reserve is reached even when the plan’s total Wh stays unchanged.

Interpret energy and output checks in order

1. Compare battery demand with usable energy first.
   A negative energy margin means the entered plan cannot finish while preserving reserve.
   Nameplate capacity shortfall and battery-side energy shortfall can differ because they use different retention and charge-window bases.
   
2. Check peak running watts against continuous AC output.
   A 50% duty appliance still needs its normal running power when it turns on; duty never halves the watt requirement in this check.
   Devices whose windows merely touch are not counted as overlapping.
   
3. Compare the simultaneous startup envelope with surge output.
   The envelope conservatively assumes every device in an overlapping window restarts together; it is not a prediction of the usual peak.
   Unknown appliance startup watts or an unknown product surge rating prevent a complete output check, even when the energy estimate looks sufficient.
   

Passing the entered W limits does not establish compatibility for voltage, frequency, waveform, VA and power factor, port limits or surge duration.
The user-check box records that you reviewed the inputs; it is not a certification.
An averaged duty cycle cannot reproduce the exact timing of compressor starts or protection-circuit behavior.

Compare quotes against the same budget

Include delivery, required cables, cases and accessories that are missing from the base quote, without double counting included items.
A positive quote difference means B costs more; it does not determine which product has better quality or is suitable.
A can be cheaper yet fail the energy requirement, as in the example.

Unknown fees are not automatically free.
Select a product’s confirmation box only after checking the actual quote scope and specifications.
Use the same currency-conversion basis for both foreign quotes and keep the model name and quote date alongside the downloaded report.
The calculator does not retrieve prices, exchange rates or product inventory.

Practical scenarios and avoiding excess capacity

If recharging is planned, enter only the no-recharge interval between charges.
Solar panel nameplate watts are not automatically converted into battery energy here.
Turning the inverter off midway also changes the idle assumption, so review such usage separately; within one plan this model keeps idle consumption active throughout.

Frequently asked questions