Why “Box Math” is Wrong
Battery Runtime Calculator
Use this lab-tuned calculator to estimate real-world runtime for your portable power station. Enter your battery size and device wattage and we’ll apply realistic efficiency standards — not the fantasy math printed on the box.
Why “Box Math” Is Wrong
Most brands quote runtime using a flawless Capacity ÷ Watts formula. That assumes
100% efficiency — no inverter loss, no heat, no wasted energy. Real hardware never behaves that way.
- AC Mode: We apply an 85% efficiency standard to account for inverter losses when you power fridges, TVs, CPAPs, and PCs.
- DC Mode: We apply a 95% efficiency standard for USB ports and 12V car outlets.
- Result: Runtimes that match what we actually see in Home Power Lab testing — not wishful thinking.
Don’t trust the number on the cardboard box. Trust the meter.
⚡ Lab-Grade Runtime Estimator
Start by entering your battery capacity in watt-hours. Then either choose a device from the list or type in its watt rating from the label or Kill A Watt meter.
- Toggle AC on for wall-outlet devices (fridge, CPAP, TV, desktop PC).
- Toggle it off for DC-only loads (USB, 12V fridge, DC lights).
- Hit Run the Numbers to see an estimated runtime in hours.
This is a planning tool — always leave buffer for startup surges, temperature, and battery age.
Battery Runtime Calculator
⚡ Lab-Grade Runtime Estimator
Example Runtimes (Based on Our Lab Tests)
Here’s how the calculator lines up with real devices we’ve tested. Your exact results will vary, but these give you a realistic ballpark:
| Battery | Device | Approx. Draw | Estimated Runtime* |
|---|---|---|---|
| EcoFlow River 2 (256Wh) | Wi-Fi Router | 15W (AC) | ≈ 14–15 hours |
| EcoFlow Delta 2 (1024Wh) | CPAP (Humidifier OFF) | 40W (AC) | ≈ 18–20 hours |
| Jackery 1000 (1002Wh) | Full-Size Fridge (running) | 150W (AC) | ≈ 5–6 hours |
*Using the same 85% AC efficiency standard as the calculator. Actual runtime depends on temperature, surge watts, battery age, and how steady the load is.
Battery Runtime Calculator – Mini FAQ
How accurate is the runtime estimate?
We use lab-verified efficiency standards (85% AC / 95% DC). Results closely match real-world runtimes, but temperature, surge loads, and aging batteries can shift actual numbers.
Why is my real runtime sometimes shorter?
Devices like fridges and compressors draw more watts than their label suggests. Inverter heat, cold weather, and battery wear also reduce available Wh.
Should I size my battery exactly to the calculated number?
No — always add at least 20–30% overhead. Critical devices such as CPAP machines deserve an even larger buffer to prevent mid-night shutdowns.
When should I use AC mode vs. DC mode?
AC Mode = Wall-outlet devices like fridges, CPAP, laptops, TVs. DC Mode = USB, 12V fridge, DC-powered CPAP using the correct converter cable.
Can I run a space heater or electric cooker?
Portable batteries can power them briefly, but the runtime is poor — a 1500W heater will drain a 1kWh power station in under an hour. These devices are generally inefficient for battery power.
Battery Runtime Calculator
Battery Runtime Calculator: Calculate the real-world runtime of any battery generator (EcoFlow, Jackery, Bluetti). Our Lab-Grade Estimator applies...
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Operating System: Web
Application Category: UtilitiesApplication