Know your real runtime before the grid goes down.
Add your devices, set inverter efficiency, and watch the battery drain live. This is a professional power‑management view — not a generic calculator.
Battery status
100%Capacity
1024 Wh
Usable
870 Wh
Remaining
870 Wh
Power station setup
Typical: 300–2000 Wh for portable stations.
AC inverters typically lose 10–20%.
Add a device
Add as many devices as you like. Runtime updates instantly.
Connected load
0 devicesTotal load
0 W
Est. runtime
∞
Energy used
0 Wh
Runtime breakdown
Usable energy
0 Wh
After inverter losses
Remaining battery
0%
After runtime target
Est. runtime
—
At current total load
Runtime target
Add devices to see how long the station can run them.
How portable power station runtime really works
Watt‑hours (Wh) — the true capacity
Portable power stations are rated in watt‑hours, not amp‑hours, because they contain lithium cells with a nominal voltage that converts directly to energy. A 1,024 Wh station can theoretically deliver 1,024 watts for one hour, or 512 W for two hours, before accounting for losses.
Amp‑hour ratings (Ah) are meaningless without voltage. A 100 Ah battery at 12 V is 1,200 Wh, but the same 100 Ah at 24 V is 2,400 Wh. This calculator uses Wh to avoid that ambiguity.
Inverter efficiency — the hidden 10–20%
AC output requires an inverter that converts DC battery voltage to 120 V or 230 V AC. That conversion is not perfect. A typical pure sine wave inverter is 85–92% efficient. If you draw 500 W AC, the battery actually supplies roughly 550–590 W.
DC and USB outputs usually skip the inverter, so they are 95–98% efficient. This is why a 12 V fridge often runs longer than a 120 V mini‑fridge with the same wattage.
Real‑world device examples
Use these typical wattages to build your load. Actual draw varies by model and usage.
| Device | Typical watts | Notes |
|---|---|---|
| Laptop | 45–90 W | Charging + use |
| Phone charging | 5–20 W | USB‑C PD or Qi |
| Wi‑Fi router | 10–30 W | 24/7 draw |
| 32″ TV | 50–80 W | LED backlight |
| Mini‑fridge (AC) | 60–100 W | Compressor cycles |
| CPAP (no humidifier) | 30–60 W | DC model saves power |
Why advertised runtime differs from real‑world runtime
1. Inverter losses. Advertised runtimes often ignore the 10–18% lost in DC‑to‑AC conversion. This calculator applies efficiency directly.
2. Depth of discharge (DoD). Most lithium stations allow 80–90% DoD before the BMS shuts off to protect cells. A “1,000 Wh” battery may only deliver 800–900 Wh. Our usable energy figure uses your starting percentage and a safe internal limit.
3. Temperature. Lithium‑ion capacity drops 10–20% in freezing conditions. Cold camping trips will not match summer ratings.
4. Device startup surges. Motors, compressors, and pumps draw 2–3× their rated wattage for a second or two on startup. A station with a 300 W continuous / 600 W peak rating may struggle with a 200 W fridge that surges to 500 W.
5. Parasitic loads. The station’s own display, BMS, and standby circuitry consume 1–5 W continuously. Over a 10‑hour run, that’s an extra 10–50 Wh.
Portable power station FAQ
How do I calculate runtime for multiple devices?+
Add the wattage of every device that runs at the same time. Sum them, then divide usable Wh by total watts. This calculator adds devices for you and shows the combined load instantly.
Should I use AC or DC output for longer runtime?+
DC and USB outputs bypass the inverter, so they are 95–98% efficient versus 85–92% for AC. If a device has a native 12 V or USB‑C option, use it for longer runtime.
What is a realistic inverter efficiency?+
Most portable stations use pure sine wave inverters rated 85–92% at half load. Efficiency drops at very low loads (under 10% of rated capacity). Default to 85% for conservative estimates.
Why does my station shut off before 0%?+
The battery management system (BMS) reserves 10–20% capacity to prevent deep discharge damage. This calculator’s “usable energy” accounts for your starting percentage, not the full nameplate capacity.
Can I run a heater or hair dryer?+
High‑wattage resistive loads like heaters (1,500 W) and hair dryers (1,800 W) will drain a 1,000 Wh station in under 30 minutes and may exceed its continuous output rating. Check your station’s continuous and peak wattage first.
How accurate is this runtime calculator?+
It gives a close estimate based on steady loads. Real runtime varies with temperature, battery age, startup surges, and parasitic draw. Use the result as a planning figure, not a guarantee.
What size power station do I need for camping?+
For a weekend trip running a CPAP, phone, LED lights, and a small fan, a 500–700 Wh station is often enough. Add a 12 V fridge and you’ll want 1,000 Wh or more. Use this calculator with your actual device list.
Does temperature affect runtime?+
Yes. Lithium‑ion batteries lose 10–20% capacity near freezing. If you’re camping in cold weather, reduce your expected runtime by 15–25% or keep the station insulated.