How Long Will an EcoFlow DELTA 3 Run a Fridge, CPAP or Space Heater?

How long will an EcoFlow DELTA 3 run a refrigerator, a CPAP or a space heater? Here are the real numbers for every model and the simple formula behind them.

The Short Answer

Every EcoFlow DELTA 3 can run a refrigerator, a CPAP and a space heater. The question is for how long, and the answer depends almost entirely on which of the three you plug in. A fridge sips power in bursts, a CPAP sips steadily, and a space heater drinks from a fire hose. Below are the real numbers for each DELTA 3 model, how we got them, and how to work out your own appliances.

How to Calculate Runtime Yourself

Runtime in hours equals usable battery capacity divided by the appliance's average draw in watts. Usable capacity is the battery's rated watt-hours multiplied by about 0.85 to account for inverter losses. So a 1,024Wh DELTA 3 has about 870Wh of usable AC power.

Runtime (hours) = (Battery Wh × 0.85) ÷ Appliance average watts

The trick is "average watts." A device's label shows its maximum draw, not what it uses over an hour. A fridge labeled 700W might average 60 to 75W because the compressor only runs about a third of the time. A space heater labeled 1,500W really does pull 1,500W the whole time it is on high. Getting the average right is the whole game.

Usable Capacity by Model

Model	Rated capacity	Usable (× 0.85)	Max with extra batteries
DELTA 3 Classic	1,024Wh	~870Wh	Not expandable
DELTA 3 / Plus	1,024Wh	~870Wh	5kWh (~4,250Wh usable)
DELTA 3 Max	2,048Wh	~1,740Wh	See product page
DELTA 3 Max Plus	2,048Wh	~1,740Wh	10kWh (~8,500Wh usable)
DELTA 3 Ultra	3,072Wh	~2,610Wh	Not expandable

Refrigerator

A modern full-size refrigerator uses about 1.2 to 1.5kWh per day, which averages out to roughly 50 to 65W across the day even though the compressor pulls 150 to 250W when it runs and can spike to 600 to 1,200W for a fraction of a second at start-up. Every DELTA 3 handles that surge; the 1kWh units are rated for 3,600W and the Ultra for 7,200W.

Model	Full-size fridge (1.35kWh/day average)
DELTA 3 Classic / DELTA 3 / Plus	About 14 to 17 hours
DELTA 3 Plus with extra battery (2kWh)	About 30 hours
DELTA 3 Max / Max Plus	About 30 hours
DELTA 3 Ultra	About 46 hours
DELTA 3 Plus expanded to 5kWh	About 3 days
DELTA 3 Max Plus expanded to 10kWh	About 6 days

Two things stretch these numbers. First, a fridge that is not opened much during an outage runs its compressor less. Second, any solar input during the day directly offsets the fridge's draw; a single 220W panel in good sun covers a fridge's average consumption several times over, which is why a DELTA 3 Plus plus one panel can keep a refrigerator going indefinitely through a sunny week.

CPAP

A CPAP machine without a heated humidifier draws about 30 to 40W. With the heated humidifier and heated tube switched on, that rises to 60 to 100W depending on the settings. Over an eight-hour night, that is roughly 0.25kWh without humidification and up to 0.8kWh with it.

Model	CPAP, no humidifier (35W)	CPAP with heated humidifier (80W)
1kWh DELTA 3 models	About 25 hours, or 3 nights	About 11 hours, or 1 night
DELTA 3 Max / Max Plus	About 50 hours, or 6 nights	About 22 hours, or 2 to 3 nights
DELTA 3 Ultra	About 75 hours, or 9 nights	About 33 hours, or 4 nights

Two practical notes for CPAP users. Many machines can run from a 12V DC cable sold by the CPAP manufacturer, which skips the inverter and gains back most of that 15 percent loss. And the DELTA 3 Plus's sub-10ms UPS switchover means you can leave the CPAP plugged into the power station full-time, with the power station plugged into the wall, and a grid outage will not interrupt therapy.

Space Heater

A space heater is the honest test of any battery. A typical unit draws 1,500W on high and 750W on low, continuously, for as long as it is switched on. There is no compressor cycling to help you. Every DELTA 3 can run one, since 1,500W is under the 1,800W continuous rating of even the smallest model, but the battery drains fast.

Model	Heater on high (1,500W)	Heater on low (750W)
1kWh DELTA 3 models	About 35 minutes	About 70 minutes
DELTA 3 Max / Max Plus	About 70 minutes	About 2.3 hours
DELTA 3 Ultra	About 1.7 hours	About 3.5 hours
DELTA 3 Max Plus at 10kWh	About 5.7 hours	About 11 hours

If heat is your priority during an outage, a battery is the wrong primary tool. A propane heater such as a Martin direct-vent heater will run for days on a tank, and the DELTA 3 is better spent on the fridge, lights and communication. Where a battery-powered heater makes sense is a heated blanket at 50 to 100W, which any DELTA 3 runs all night, or a heater with a thermostat that cycles on and off in a small, well-insulated room.

Other Common Loads, Quick Reference

Using the same 0.85 factor and typical draws, here is how long a 1kWh DELTA 3 runs each of the following. Double for a Max, triple for an Ultra.

• Wi-Fi router and modem (15W): about 58 hours.
• Laptop (50W): about 17 hours.
• 55-inch LED TV (100W): about 8.7 hours.
• Chest freezer (1kWh/day, about 42W average): about 21 hours.
• Sump pump, 1/3 HP (800W running, cycling 10 minutes per hour): roughly 6 to 7 hours of coverage.
• Microwave (1,000W): about 50 minutes of cooking time, or dozens of individual reheats.
• Electric kettle (1,200W): about 43 minutes, or roughly 12 to 15 full boils.
• Window air conditioner, 5,000 BTU (450W): about 1.9 hours continuous, longer with thermostat cycling.
• Phone charging: about 60 to 80 full charges.

Three Ways to Get More Runtime

1. Add solar. This is the single biggest lever. A DELTA 3 Plus with 1,000W of panels refills in about 70 minutes of good sun, and even one 220W panel will offset a fridge's entire daily draw. Our solar panel pairing guide explains what fits each model.
2. Add a battery. A DELTA 3 or Plus grows to 5kWh; a Max Plus grows to 10kWh. That turns a day of fridge into three to six. See the expansion battery guide.
3. Cut the load. Run the fridge, not the freezer and fridge. Use the CPAP without the humidifier. Swap the space heater for a heated blanket. Small choices double runtime.

All DELTA 3 models are in stock at Wild Oak Trail with solar and battery bundles in the EcoFlow collection.

Frequently Asked Questions

How long will an EcoFlow DELTA 3 run a refrigerator?

A 1kWh DELTA 3, DELTA 3 Plus or Classic runs a typical full-size refrigerator for about 14 to 17 hours. The 2kWh DELTA 3 Max runs one for about 30 hours, the 3kWh DELTA 3 Ultra for about 46 hours, and a DELTA 3 Plus expanded to 5kWh for about three days.

Can an EcoFlow DELTA 3 run a CPAP all night?

Yes. Without a heated humidifier a CPAP draws about 35W and runs for roughly 25 hours, or three nights, on any 1kWh DELTA 3. With a heated humidifier, expect about one night per kilowatt-hour of battery.

How long will a DELTA 3 run a 1,500W space heater?

About 35 minutes on a 1kWh model, about 70 minutes on the DELTA 3 Max, and about 1.7 hours on the DELTA 3 Ultra. On the 750W low setting, roughly double those figures. A battery is not an efficient way to heat a room; a propane heater is a better primary heat source in an outage.

How do I calculate how long a power station will run an appliance?

Multiply the battery's watt-hours by 0.85 to account for inverter losses, then divide by the appliance's average wattage. A 1,024Wh DELTA 3 has about 870Wh usable; divided by a 50W laptop, that is about 17 hours.

Can the DELTA 3 handle a refrigerator compressor starting up?

Yes. Fridge compressors briefly spike to 600 to 1,200W at start-up. Every DELTA 3 model surges to at least 3,600W, so the start-up is not a concern.

What is the best way to extend DELTA 3 runtime?

Add solar. Even a single 220W panel covers a refrigerator's average daily draw in good sun, and the DELTA 3 Plus accepts up to 1,000W of panels for a full recharge in about 70 minutes. Adding an extra battery is the second-best option, raising the DELTA 3 Plus to 5kWh or the Max Plus to 10kWh.