Power Station Runtime Calculator
Select the devices you need to run, pick a duration, and get a recommended battery size — computed live from this project's 20-entity verified dataset.
1. Select Your Devices
2. How Long Do You Need Power?
3. Matching Power Stations
Select at least one device and a duration to see results.
How to Calculate Power Station Runtime
Runtime is capacity divided by load — but only after taking out what the inverter loses turning stored DC into mains AC. Skipping that step is why a unit that looks like it should last all night runs out hours early.
Working the other way, to size a unit before buying it, the calculator above adds a safety margin on top:
The 0.75 is AC inverter efficiency: roughly a quarter of the stored energy is lost as heat in the conversion. Running a device from a DC or USB port skips the inverter and loses far less, which is why a DC-only fridge outlasts the same fridge on an AC plug. The 1.1 adds a 10% buffer so a unit is not sized to finish at exactly zero.
Typical Device Wattages
These are the running-watt figures the calculator uses. They are planning figures for common appliance classes, not measurements of any specific model — check the plate on your own device where the exact number matters.
| Device | Category | Running watts | Hours from 1024 Wh |
|---|---|---|---|
| CPAP (no humidifier) (needs pure sine wave) | Medical | 30 W | 25.6 h |
| CPAP (heated humidifier) (needs pure sine wave) | Medical | 75 W | 10.2 h |
| Oxygen concentrator (stationary) (needs pure sine wave) | Medical | 330 W | 2.3 h |
| Mini-fridge | Home | 100 W | 7.7 h |
| RV fridge | Home | 250 W | 3.1 h |
| Window AC unit (running) | Home | 700 W | 1.1 h |
| Space heater | Home | 1500 W | 0.5 h |
| Sump pump (running) (needs pure sine wave) | Home | 800 W | 1.0 h |
| Television | Home | 150 W | 5.1 h |
| Box fan | Home | 75 W | 10.2 h |
| Laptop | Office | 65 W | 11.8 h |
| Wi-Fi router | Office | 10 W | 76.8 h |
| Monitor | Office | 55 W | 14.0 h |
| Phone charger | Office | 10 W | 76.8 h |
| Coffee maker | Kitchen | 1200 W | 0.6 h |
Last column assumes one EcoFlow DELTA 2 (1024 Wh) running that device alone on AC. Fridges and air conditioners cycle on and off rather than drawing continuously, so they last longer in practice than a flat division suggests.
Worked Example
A home-office outage load on the EcoFlow DELTA 2 (1024 Wh):
- Mini-fridge — 100 W
- Laptop — 65 W
- Wi-Fi router — 10 W
- Total load: 175 W
- 1024 Wh × 0.75 ÷ 175 W = about 4.4 hours
Swap the laptop for a 1500 W space heater and the same unit is empty in well under an hour. Heating elements are what capacity planning turns on — everything else on this list is rounding error by comparison.
Power Station Runtime: Common Questions
How long will a 1000Wh power station run a fridge?
On the flat arithmetic, a 1,000Wh unit running a 100W mini-fridge gives about 7.5 hours after inverter loss. In practice it runs far longer, because a fridge compressor cycles rather than drawing continuously — at a 40% duty cycle the same unit covers closer to 18 hours.
Why does my power station die faster than the calculator says?
Usually one of three things: the load is higher than the figure you entered (a kettle or heater pulls its full rating the whole time it is on), the unit is being asked for AC through the inverter rather than DC through a USB or car port, or it is cold. Lithium cells deliver 10-30% less usable energy below room temperature.
Does running devices from the USB ports last longer?
Yes. USB and 12V car ports draw straight from the battery and skip the AC inverter, so they avoid the roughly 25% conversion loss this calculator applies. A device that can be run on DC will typically last about a third longer than the same device on an AC plug.
What size power station do I need for a 3-day outage?
Add the running watts of everything you genuinely need, multiply by the hours per day each item runs, then multiply by three days and divide by 0.75 for inverter loss. Most households sizing for essentials only — fridge, phones, router, lights, a fan — land between 2,000Wh and 4,000Wh, which usually means a unit plus expansion battery or solar recharge rather than a single box.
Methodology: total wattage × hours ÷ 0.75 AC-inverter efficiency factor × 1.10 safety margin = recommended Wh. Devices marked ⚕️ require a confirmed pure sine wave inverter — units with an unconfirmed or non-pure-sine-wave inverter are excluded automatically, not just deprioritized.