Which EcoFlow can run your AC or heater?

The three numbers that decide what an EcoFlow can run

Before any model names, these three spec-sheet numbers do all the work, and confusing them is where most bad buying decisions start.

• Capacity, in watt-hours (Wh), decides how long it runs. This is the size of the tank. A 1,024 Wh Delta 2 holds about a kilowatt-hour of usable energy, minus some to conversion loss.
• Continuous output, in watts (W), decides whether it runs the load at all. This is the engine size. A unit rated 1,800 watts can feed an 1,800-watt draw steadily; ask for more and it either boosts briefly or shuts off.
• Surge, in watts, decides whether it can start a motor. An air conditioner or compressor pulls a spike far above its running draw for the first fraction of a second, and the station has to survive that spike. This is the number people skip, and it is the one a window AC most often trips.

So a unit can have a big tank and still be unable to start your AC, and a unit that starts anything can still empty in an hour on the wrong load. Every question below is really about which of these three numbers is the limit for your equipment.

Which EcoFlow do you need for a window air conditioner?

A window air conditioner is the classic question, and the surge is what decides it. A standard window unit with an ordinary compressor pulls two and a half to three and a half times its running watts at the instant it starts, so the startup spike, not the steady draw, is what the station has to clear. Rough running and starting numbers by size:

One thing changes this table completely: whether the AC is an inverter model. An inverter window unit ramps its compressor up gently instead of slamming it on, so its startup surge is only around a third more than its running watts, not triple. That means an inverter 12,000 BTU unit can start on a Delta 3 that would stall trying to start a standard 12,000 BTU unit. If you are buying the AC and the EcoFlow together, an inverter AC is the one that lets you get away with a smaller station.

Does X-Boost let a smaller EcoFlow run my AC?

No, and this is the single most misunderstood thing about these units, so it is worth being exact. X-Boost is EcoFlow's feature that lets a station run a device rated above its continuous watts by lowering the output voltage, keeping the total wattage under the inverter's ceiling. It works because a resistive device, a space heater, a kettle, a hair dryer, simply runs a little cooler at lower voltage with no harm done. For resistive loads, X-Boost is genuinely useful.

A motor is a different animal. Dropping the voltage to a compressor makes it draw more current to compensate, which adds heat and can stall it, and more to the point, X-Boost governs the steady running wattage, not the split-second startup surge. The surge is handled by the station's separate peak rating, which X-Boost does nothing to raise. So X-Boost will not make a window air conditioner start that could not start otherwise. If the AC's startup surge is above the unit's peak, no X-Boost setting fixes it; you need a bigger EcoFlow or a soft start added to the air conditioner.

Can an EcoFlow run a mini-split?

Yes, and a ductless mini-split is one of the friendliest real HVAC loads for an EcoFlow, for the same reason an inverter window unit is. Its inverter compressor eases up to speed instead of snapping on, so there is almost no startup spike to clear, and you can size the station by running watts alone against its continuous rating. A single indoor head pulls anywhere from about 300 watts for a small unit loafing along to roughly 1,800 watts for a big one working hard, and because it throttles back once the room is at temperature, the everyday draw usually sits well below that top figure.

In practice a Delta 2 or Delta 3 runs a smaller 115-volt mini-split, and you step up to a Delta Pro or Delta Pro 3 for a larger 18,000 or 24,000 BTU unit, many of which are 240 volts and need a unit that supplies it. A Delta Pro running a 12,000 BTU mini-split that has settled to around 500 watts lasts six to seven hours and longer as it modulates down. Of the things people actually want to run in an outage, a mini-split is where an EcoFlow shines.

Can an EcoFlow keep my furnace running during a power outage?

If your furnace burns gas or oil, yes, easily, and this is the best outage story an EcoFlow has for heat. The burner does the heating on fuel, so the station is only feeding the electrical bits: the fan that circulates the warm air, the ignition, and the small motor that vents the exhaust. A variable-speed fan sips under 300 watts and an older single-speed one wants somewhere around 500 to 800 watts, which is a light, steady draw either way. A Delta 2 keeps a 250-watt fan going for several hours nonstop, and far longer in practice because the furnace only fires in bursts, while a Delta Pro rides right through the night.

The catch is only if your heat itself is electric. A battery running a gas furnace is powering a few hundred watts of fan and controls; a battery running electric resistance heat is powering the heat itself, which is a different order of magnitude, covered next. So the rule is simple: a gas or oil furnace on an EcoFlow is a comfortable overnight job, and an electric furnace is not.

Why does a space heater drain an EcoFlow so fast?

Because a heating element converts every watt directly to warmth with none of the multiplier a heat pump gets, and warmth is expensive in watts. A plug-in heater sits at 1,500 watts, the ceiling a normal outlet allows, and it holds that draw flat out with none of the on-off cycling that stretches an air conditioner. X-Boost does apply here, since the element is resistive, but that only affects whether a smaller unit can feed it, not how long the charge lasts.

The math is unforgiving. A 3,600 Wh Delta Pro running a 1,500-watt heater lasts about two hours. A 1,024 Wh Delta 2 lasts about forty minutes. That is the worst return of any HVAC load you can put on a battery, and it catches people who assume heat is easy. If staying warm in an outage is the goal, the far better plan is to power a gas furnace's blower or a mini-split, both of which run for many hours, rather than a resistance heater that empties even a large unit before you are through the evening.

Can any EcoFlow run central air conditioning?

For a portable station, no. A central air conditioner runs on a 240-volt circuit and its compressor pulls an enormous startup surge, on the order of fifteen to twenty thousand watts for a fraction of a second on a typical home system, which is far beyond what a portable unit can deliver. The River and Delta 2 and Delta 3 units are 120 volts only, and even a single classic Delta Pro is 120 volts until you pair two of them through a Smart Home Panel. None of them starts a central AC.

The only EcoFlow that credibly backs a central system is the Delta Pro Ultra class, which is a stackable whole-home battery with native 240-volt output measured in tens of kilowatts, and even that generally needs a soft start added to the air conditioner to tame the startup surge. A single Delta Pro 3, which is natively 240 volts, can reach a small central system only with a soft start, and that is a possible-not-guaranteed situation rather than a clean yes. At that point you are really shopping for a home battery, not a portable power station, which is a different decision covered in our guide to running your HVAC on a home battery.

How long will an EcoFlow run each HVAC load?

The estimate is straightforward: take the capacity in watt-hours, trim it by about fifteen percent for conversion loss, and divide by the running watts. Cooling and heating that cycle on and off stretch further than that in mild weather, but the worst-case number is a good planning figure. The contrast across one 1,024 Wh Delta 2 and one 3,600 Wh Delta Pro is below.

Those are single-unit figures, and every Delta can take one or more extra batteries to multiply them. To size it for your own equipment and the exact appliances you want to keep running, our generator sizing calculator totals the running and starting watts the same way a power station has to meet them.

Which EcoFlow should you buy for your HVAC?

Start from the heaviest thing you want to run, since that sets the model, and remember the newer Delta 3 line has largely replaced the Delta 2 line while the older units stay on shelves at a discount. A rough guide:

• Just a gas furnace blower or a small mini-split: a Delta 2 or Delta 3 (around 1,000 Wh, 1,800 watts) is plenty, and a River 3 Plus can cover a low-draw ECM blower alone.
• A window AC or a larger mini-split: a Delta 2 Max or Delta 3 Max (around 2,000 Wh, 2,400 watts, higher surge) gives the headroom to start a bigger unit and run it longer.
• A window AC plus other loads, or you want most of a night: a Delta Pro or Delta Pro 3 (3,600 to 4,000 watts, larger tanks, expandable) is the comfortable choice, and the Delta Pro 3 adds native 240-volt output.
• Anything approaching central air or whole-home backup: that is Delta Pro Ultra territory, a stackable 240-volt home battery, and it belongs to the home-battery decision rather than the portable one.

Two reminders as you choose. The capacity number tells you how long it lasts, the output number tells you whether it runs the load, and the surge number tells you whether it starts a motor, so check all three against your equipment, not just the price. And if a window AC is the sticking point, adding a soft start to the air conditioner, or choosing an inverter model, can let a smaller and cheaper EcoFlow do the job. If you are also cross-shopping brands or a permanent battery, our EcoFlow vs Jackery vs Tesla Powerwall comparison weighs the whole field.