Emily ParkerBy Emily Parker

Updated November 2026

The EcoFlow Delta 2 Pro Max is a portable power station that can keep essential household loads running during a power outage. To use it well, you need to match its stored energy to what you plan to power, then estimate how long that energy will last. This guide walks through that math for a refrigerator, a CPAP machine and a sump pump.

Step 1: Find the Battery Capacity

Start with the battery capacity printed in the product specifications. Manufacturers list it in watt-hours (Wh), which is the amount of energy the battery can deliver at a steady rate for one hour. Remember that real-world output is lower than the rated number because of conversion losses in the inverter, typically somewhere around 10 to 20 percent depending on load and temperature. Plan around the usable figure, not the label.

Shopping for one? See our guide: EcoFlow Delta 3 Max Plus Review: Features and Performance.

Step 2: Calculate the Watt-Hours Each Device Needs

For each device, multiply its running wattage by the hours it will run per day. Check the nameplate or manual for wattage. Many appliances cycle on and off, so a fridge does not run at full draw all day. A common rough estimate for a modern refrigerator is 150 to 400 Wh per day, but the figure varies with model, age, kitchen temperature and how often the door is opened.

Some typical loads to plan around:

  • Refrigerator: Often 150 to 400 Wh per day on average, with high startup surges. Confirm with your appliance’s energy label or a plug-in energy meter.
  • CPAP machine: Commonly around 30 to 90 W while running. Overnight use of 8 hours can easily land between 250 and 700 Wh, depending on humidifier use and the model.
  • Sump pump: Usually 300 to 1,000 W while pumping, but it runs only in short bursts. Your daily total depends on how often water rises and how long each cycle lasts.

Step 3: Build a Runtime Estimate

Add the daily watt-hours for every device you want to keep running, then apply a safety margin. A practical formula looks like this:

Usable Wh divided by total daily Wh equals approximate hours of runtime.

Suppose you want a fridge (300 Wh per day), a CPAP (500 Wh per night) and occasional sump pump use (200 Wh per day). That totals about 1,000 Wh. If your estimate of usable energy is around 2,700 Wh after losses, you can expect roughly two and a half days of that combined load, assuming no solar recharging. Real results will differ, so treat the number as a planning figure rather than a guarantee.

Step 4: Plan Recharging and Load Priorities

Runtime only matters if you can recharge or stretch the energy. The Delta 2 Pro Max accepts AC wall charging, and many owners pair it with solar panels for extended outages. Check the product’s solar input specifications before buying panels, since input limits determine how fast you can recharge. You can read more about panel sizing in Solar Panels for EcoFlow Delta Pro: How to Choose and Connect Them (2026).

Prioritize loads. Keep the CPAP and refrigerator at the top of the list, and run the sump pump on a schedule or only when water is rising. Turning off nonessential outlets and limiting high-draw appliances such as space heaters or microwaves will extend your runtime considerably.

Sizing Reference Table

Load Typical Daily Use Planning Note
Refrigerator 150 to 400 Wh Varies with model and door openings
CPAP (8 hours) 250 to 700 Wh Humidifier adds energy use
Sump pump Highly variable Depends on water inflow

Common Mistakes to Avoid

  • Using the rated capacity as if it were fully usable energy.
  • Ignoring startup surges from compressors and pumps, which can exceed running wattage.
  • Forgetting that a CPAP or sump pump may run longer during a storm than on a normal day.
  • Skipping a test run before the outage so you know how the setup behaves.
  • Plug-in energy meter: Measures actual watt-hours used by each appliance, which is more reliable than guessing from nameplates. View on Amazon
  • Solar panels compatible with EcoFlow stations: Extend runtime during multi-day outages when sunlight is available. View on Amazon
  • Heavy-duty extension cord rated for outdoor use: Helps route power safely from the station to outlets or appliances. View on Amazon

FAQ

Can the EcoFlow Delta 2 Pro Max run a refrigerator all night?

Often yes, since many refrigerators use a few hundred watt-hours per day. Measure your own unit with an energy meter to confirm, because older or larger models use more.

How long will a CPAP run on this power station?

Runtime depends on the CPAP’s wattage, humidifier use and the usable capacity you have left. Calculate from the machine’s nameplate wattage and hours of use for an estimate.

Should I consult a professional before setting up backup power?

Yes, especially if you plan to connect the station to home circuits. A licensed electrician can advise on safe transfer methods and load limits.

Conclusion

To use the EcoFlow Delta 2 Pro Max for home backup, match its usable watt-hours to your real daily loads and build in a margin for losses. Prioritize essential devices like a CPAP and refrigerator, and plan a recharge method if outages may last several days. Test the setup before you need it.

Ready to choose one?

Emily Parker

About Emily Parker

Emily Parker is part of our editorial team and reviews and edits our solar generators for home backup & emergencies guides, checking product details against manufacturer specifications and owner feedback.