The runtime calculator

How long will your
power station last?

Pick your appliances, set their on-time, and see the battery capacity and output your plan needs.

Official-source defaultsEvery assumption visible

Wh tells you how long.
W tells you what can run.

We’ll help you check both.

01 / Battery size

Your power station

Battery capacity (Wh)

Use the capacity on the spec sheet. Wh is energy; W is output.

Losses & output limits

Example losses from the AC180 manual, §4.4.3. Adjust for your station. A capacity choice does not set its output rating.

Usable capacity (%)Inverter efficiency (%)AC overhead (W)

Optional: enter the maker’s normal output and surge ratings to check this load. Check surge duration in its manual too.

Continuous output (W)Surge output (W)

02 / Build your load

What are you running?

Make a plan

Example hours are editable. Use actual on-time per unit.

Plan length (hours)

Device hours are capped to the plan length. For a fridge or pump, count time actively running.

Wi-Fi router

15 W running 15 W starting

QuantityOn-hours120Wh / plan

Edit wattsOne router or modem. Add each separately.

Wi-Fi router running wattsWi-Fi router total starting watts

Starting watts include running watts. Maker’s reference: 10–20 W running; No extra in chart starting. Use your device’s input label or measured draw.

Laptop

65 W running 65 W starting

QuantityOn-hours260Wh / plan

Edit wattsAC charger; draw changes while charging.

Laptop running wattsLaptop total starting watts

Starting watts include running watts. Maker’s reference: 20–100 W (charger) running; No extra in chart starting. Use your device’s input label or measured draw.

LED light

10 W running 10 W starting

QuantityOn-hours80Wh / plan

Edit wattsPer bulb; set the quantity you need.

LED light running wattsLED light total starting watts

Starting watts include running watts. Maker’s reference: 8–15 W per bulb running; No extra in chart starting. Use your device’s input label or measured draw.

Add an appliance3 selected

Editable planning values from Champion’s wattage chart, not measurements of your devices.

Assume all devices start togetherOff: one unit starts at a time. On: allow overlapping starts.

03 / Your estimate

Estimated runtime

10.6hours

At an average planned draw of 72.5 W, including overhead.

Running load100 W

Starting surge100 W

Running total + the largest single extra starting burst.

Output not fully checked. Enter both ratings above.

Your 8-hour energy plan

Available after losses765 Wh

Plan + overhead580 Wh

Same scale for both bars.

Enough estimated energy for this plan.

Assumes your usage pattern repeats evenly. Device order can change actual runtime. With every selected device on continuously: about 6.7 h on energy alone.

90% usable × 85% inverter · 15 W overhead · no recharging. Source: AC180 example

Find stations for this plan

Filters: at least 1,000 Wh, 100 W continuous and 100 W surge. Uses your chosen size or the larger size this plan needs. Verify the maker’s specifications.

Where the energy goes

Wi-Fi router120 Wh

Laptop260 Wh

LED light80 Wh

Inverter overhead120 Wh

See your estimate~10.6 h

The numbers, explained

A useful estimate. With the working shown.

Allow for losses

We start with 90% usable battery capacity, then 85% inverter efficiency, with 15 W of AC overhead. These are editable examples from the BLUETTI AC180 manual, §4.4.3, not universal power-station specifications. We count overhead throughout the plan.

Use real on-time

Energy is running watts × quantity × hours. A fridge may stay plugged in while its compressor cycles; use actual compressor-on hours. The sample plans are editable examples. Runtime extends your plan’s average draw, assuming the same pattern repeats evenly. It does not model device order.

Leave room to start

Check continuous output against the running total. For one startup at a time, surge is that total plus the largest single (starting − running) burst. If devices can start together, select that option to add every burst, including quantities. A short surge rating must last long enough for the appliance.

Check it by hand

A 1,000 Wh example

Available energy: 1,000 Wh × 0.90 × 0.85 = 765 Wh after capacity and conversion allowances.
An 8-hour plan: 15 W router × 8 h + 65 W laptop × 4 h + 2 × 10 W lights × 4 h = 460 Wh for appliances.
Include overhead: 460 Wh ÷ 8 h + 15 W = 72.5 W average draw in this approximation.
Estimated runtime: 765 Wh ÷ 72.5 W ≈ 10.6 hours. Required nameplate capacity for the 8-hour plan: (460 + 15 × 8) ÷ (0.90 × 0.85) ≈ 759 Wh, rounded up.

AC outlet use only, starting from a full charge, with no solar or other charging during discharge. Temperature, battery age, changing draw, standby behavior and conversion losses can alter runtime. This is an energy-budget approximation, not a runtime guarantee. For cycling loads, use measured energy and the maker’s startup requirements to refine the estimate.

A starting point, not a measurement

Appliance wattage reference

Read the maker’s chart ↗

Editable planning defaults. Starting W is the total during startup, not extra watts.
Appliance	Running	Starting	Published running / starting range
FridgeCount compressor-on time; cycling varies.	200 W	1,200 W	150–400 W 800–1,200 W
CPAP · no heatWithout heated humidification or tubing.	60 W	60 W	30–60 W No extra in chart
Wi-Fi routerOne router or modem. Add each separately.	15 W	15 W	10–20 W No extra in chart
LaptopAC charger; draw changes while charging.	65 W	65 W	20–100 W (charger) No extra in chart
LED lightPer bulb; set the quantity you need.	10 W	10 W	8–15 W per bulb No extra in chart
TV32–55 inch example; check your label.	100 W	100 W	80–400 W No extra in chart
Space heaterHigh setting; a large continuous load.	1,500 W	1,500 W	750–1,500 W No extra in chart
Sump pump⅓ HP example; count actual pumping time.	800 W	1,600 W	500–800 W 1,000–1,600 W
MicrowaveUse electrical input watts from the label.	1,200 W	1,200 W	600–1,200 W No extra in chart
FanWindow / box fan example.	75 W	75 W	50–200 W No extra in chart
FreezerCount compressor-on time.	200 W	1,000 W	100–500 W 500–1,000 W
Window AC5,000 BTU example; count compressor-on time.	600 W	1,200 W	450–600 W 900–1,200 W
CPAP · with heatHeated humidifier example; settings matter.	120 W	120 W	60–120 W No extra in chart
Security systemHome security system example.	25 W	25 W	15–40 W No extra in chart

Defaults are selected planning values within Champion’s ranges. “No extra in chart” means the reference lists no additional starting load; the default total starting watts equal running watts. Your device may differ. For a microwave, use the electrical requirements in its manual. On small screens, scroll the table to see the source ranges.

Direct from the source

References behind the estimate

Champion · appliance wattage chart
Running and starting ranges for each appliance. Our editable starting points sit within these ranges; they are not measurements of your equipment.
BLUETTI · AC180 manual, §4.4.3 (PDF)
The source of our example 90% usable capacity, 85% inverter efficiency and 15 W overhead. These describe the AC180 example, not every station. The manual also notes the effects of temperature and load.
Champion · sizing running and starting loads
The maker’s worked sizing examples add the largest starting differential to the running total when devices start separately. Check the duration of your station’s surge rating.
GE Appliances · microwave electrical requirements
Use the microwave’s electrical requirements in its owner’s manual or installation instructions when checking power needs.

Turn your plan into a shortlist.

Start with capacity. Then verify continuous output, surge duration and the connections you need.

Explore power stations