What will you run at the same time?
Estimated runtime
-
- Total load
- - W
- Usable energy
- - Wh
Formula: capacity × usable share ÷ total watts. Wattages are typical examples: replace them with the figure on your device label, or better, a reading from a plug-in watt meter. Fridges and freezers cycle on and off, so we use an average draw; their start-up surge is higher.
How the calculation works
Station presets come from the capacity and continuous output listed in our power station guide, based on manufacturer specs. Device wattages are illustrative typical values: your exact models will differ.
Watts vs watt-hours
Watts (W) measure how much power a device draws right now. A station's continuous output (W) must exceed the total of everything running together. Watt-hours (Wh) measure energy over time: the battery's tank size. A 60 W device for 10 hours uses 600 Wh.
Three tips for accurate numbers
- Measure: a plug-in watt meter on your fridge for 24 hours gives its real daily Wh.
- Separate surge: motors (fridges, pumps) briefly draw several times their running watts when starting.
- Prefer DC: charging phones and laptops from USB-C avoids inverter losses.
FAQ
How accurate is this calculator?
It is as accurate as the watt figures you enter. The preset wattages are typical examples only; measure your devices with a plug-in watt meter for reliable results. Battery age, temperature and inverter efficiency at low loads also affect real runtime.
Why 85% usable energy?
Converting battery DC to household AC loses energy in the inverter, and stations keep a small reserve. 85% is a common planning figure; DC loads (USB-C, 12V) often lose less. Adjust the slider to your situation.
Why does my fridge show such a long runtime?
A fridge's compressor cycles on and off, so its average draw over a day is much lower than its running watts. We use average draw for runtime. The start-up surge still needs to fit within the station's surge rating.
Can I embed or share this calculator?
You can link to this page freely.