CPAP battery backup: sizing and runtime math

Sizing a battery to a CPAP is unusually tractable, because the draw is small, steady and published. The complication is that there is no single number: the same machine can draw roughly 11 W or roughly 59 W depending on one setting. This guide works the arithmetic from ResMed's own documents and shows the assumptions.

Two things first. Nothing here is medical advice, and none of the products below is a medical device. Whether a given power source is appropriate for your therapy device is a question for the device manufacturer and the provider who supplied it. We have not tested any of these units with any CPAP. The Amazon links above are affiliate links, disclosed at the top of this page.

What a CPAP actually draws

Two different published bases exist, and they answer different questions.

The AC side. ResMed's user guides publish a typical and a peak power consumption for the machine plus its power supply. The AirSense 10 user guide lists a 90W power supply, 24V at 3.75A DC output, typical power consumption of 53 W (57 VA) and peak power consumption of 104 W (108 VA). The AirSense 11 user guide lists a 65W power supply, 24V at 2.71A, typical power consumption of 56.1 W (111.5 VA) and peak of 73.2 W (137.6 VA). We took those from the current Americas edition, document 398291/1, dated June 2025, and confirmed the identical block in the current European, Asia-Pacific and Australia and New Zealand editions. These are the figures that apply when you plug the machine's own adapter into a power station's household outlet.

Two caveats on them. The guides do not state which humidifier setting the typical figure was measured at, and the DC table below strongly suggests a figure this high is a humidifier-active one. And there is an older number still circulating: ResMed's original 2021 US edition, document 398001/1, printed 9.0 W typical against a 71.9 W peak. That edition has been superseded, the peak barely moved while the typical figure changed by a factor of six, and the current guide in every region we could reach says 56.1 W. If you find a low CPAP wattage quoted online with no document number attached, that is usually where it came from. Read the values off the edition that came in your box.

The DC side. ResMed's battery guide (document 198103/7) publishes current draw at 12V DC for each device, tubing and humidifier combination, at each treatment pressure. For the AirSense 10 with SlimLine tubing at 10 cmH2O:

| Configuration | Current at 12V DC | Watts (amps x 12V) |

|---|---|---|

| No humidifier | 0.93 A | 11 W |

| Humidifier at setting 4 | 2.30 A | 28 W |

| Humidifier at setting 8 | 3.66 A | 44 W |

| ClimateLineAir at 30 C plus humidifier at 8 | 4.92 A | 59 W |

That is the load-bearing fact of this whole guide. Turning the humidifier from off to setting 8 multiplies the draw by roughly four. Adding heated tubing on top pushes it past five times. Nothing you can buy changes the arithmetic as much as that one setting does.

One caveat on provenance: ResMed's published battery guide covers the AirMini, Stellar, Air10 and S9 families. The AirSense 11 is not in its tables. For an AirSense 11 the published figures available are the user guide's AC typical and peak, without a humidifier breakdown.

The runtime table

Runtime at the ceiling is rated capacity divided by load. Below, four capacities against four published load figures. The assumptions are stated because they change the answer: these use each unit's rated Wh, not usable Wh, and they ignore inverter losses, the battery's low-voltage cutoff and the station's own standby consumption. Real runtime is lower than every number in this table. None of these makers publishes an inverter efficiency figure for a load this small, so we do not apply a derate rather than invent one.

| Rated capacity | At 11 W | At 28 W | At 44 W | At 56 W |

|---|---|---|---|---|

| 286 Wh (RIVER 3 Plus) | 26.0 h | 10.2 h | 6.5 h | 5.1 h |

| 1,024 Wh (Elite 100 V2, DELTA 3 Plus) | 93.1 h | 36.6 h | 23.3 h | 18.3 h |

| 1,056 Wh (SOLIX C1000) | 96.0 h | 37.7 h | 24.0 h | 18.9 h |

| 1,070 Wh (Explorer 1000 v2) | 97.3 h | 38.2 h | 24.3 h | 19.1 h |

The more useful way to read that is per night. An 8-hour night costs 88 Wh at 11 W, 224 Wh at 28 W, 352 Wh at 44 W and 448 Wh at 56 W. So the 286 Wh unit covers roughly three nights with the humidifier off, and does not cover a single 8-hour night at the AirSense 11's published AC typical figure. The 1 kWh class covers a long weekend humidified, or well over a week dry, at the ceiling. Shade all of it down for losses.

AC outlet or DC converter

The picks here are power stations, which means the default plan is to plug the machine's own AC adapter into a household outlet on the unit. ResMed publishes a preference against that path when a battery is the source.

Its battery guide states: "We strongly recommend using DC-to-DC converters to power your ResMed device from a battery rather than DC-to-AC inverters." The reasons it lists are concrete: converters are more efficient, provide electrical protection if leads are connected incorrectly, regulate battery voltage, and "shutdown automatically when the voltage drops below a certain threshold and protects the battery from damage by not allowing a full discharge."

If you use an inverter anyway, ResMed recommends "a pure sine wave inverter with a continuous power rating of 300 watts and a peak/surge rating of 500 watts," and explains that "modified sine wave converters alternate voltage in steps which can damage sensitive electronics." Every unit on this page exceeds 300 W continuous by a wide margin, so the output rating is not the constraint. The waveform is, and here the spec sheets diverge:

• Anker states "1800W Pure Sine Wave" directly in the SOLIX C1000 specs.
• BLUETTI lists "Inverter Type: Pure Sine Wave" for both the Elite 100 V2 and the Elite 200 V2.
• EcoFlow does not state the waveform on the RIVER 3 Plus, DELTA 3 Plus or DELTA Pro 3 product pages, and Jackery does not state it on the Explorer 1000 v2 page. That is an absence of a published claim, not evidence of a modified sine wave. If the waveform matters to you, ask the maker before buying.

The DC path has its own gating spec: the station needs a 12V output for ResMed's converter to plug into. Four of the five picks publish one. The Anker SOLIX C1000 lists a 120W, 12V/10A cigarette lighter output; the BLUETTI Elite 100 V2 lists 1 x 12V/10A car outlet; the Jackery Explorer 1000 v2 lists a 12V, 10A car port; the EcoFlow DELTA 3 Plus lists 12.6V, 10A, 126W max. The EcoFlow RIVER 3 Plus publishes a car input but no DC output row at all, so on the RIVER 3 Plus the AC outlet is the only route.

ResMed also publishes device-specific warnings in the same guide, including that certain of its heated humidifiers must not be used with inverters at all. Those warnings name specific older models rather than the AirSense line, which is exactly why the right move is to read your own device's documentation rather than generalize from ours.

Travel is a different problem

Every unit here is too large to fly with. The FAA's PackSafe guidance for lithium batteries sets the threshold for passenger baggage at 100 watt hours per battery without airline approval, permits batteries "exceeding 101-160 Wh" with airline approval up to two spares, and states that above that they are "forbidden." It also requires that "spare (uninstalled) lithium ion and lithium metal batteries, including power banks and cell phone battery charging cases, must be carried in carry-on baggage only."

The smallest pick on this page is 286 Wh. That is not a flaw in these products; it is a different product category. Purpose-built CPAP travel batteries are engineered under 100 Wh precisely so they clear the rule. If your requirement is air travel rather than home outages, this is the wrong page. Confirm the current rules with the FAA and your airline before you pack anything.

Choosing between them

• You want the smallest thing that does the job, for a bedside outage: the EcoFlow RIVER 3 Plus at 286 Wh, on the understanding that it is a humidifier-off answer.
• You want it to take over automatically when the power drops: a unit with a published UPS switchover. BLUETTI lists 10 ms or less for the Elite 100 V2, and EcoFlow lists under 10 ms for the RIVER 3 Plus and DELTA 3 Plus. Anker publishes under 20 ms for the SOLIX C1000. Jackery's 20 ms figure appears in page copy rather than the Explorer 1000 v2 spec table, so we treat it as unpublished. Pass-through operation means the machine stays plugged into the station and the station stays plugged into the wall.
• You want maximum margin with no thinking: any of the 1 kWh class. The Anker SOLIX C1000, Jackery Explorer 1000 v2 and EcoFlow DELTA 3 Plus sit within 50 Wh of each other, and all three carry inverter ratings many times a CPAP's draw.
• You expect the requirement to grow: the EcoFlow DELTA 3 Plus accepts additional batteries, so capacity can be added without replacing the inverter.

For how these units compare on the specs that matter for backing up a whole house rather than one device, see our plug-in backup guide. For the choice between a portable unit and an installed system, see portable power station vs home battery. For why rated capacity and usable capacity differ, see depth of discharge, and for the underlying unit arithmetic, kWh explained.

Every device figure above is quoted from a manufacturer document with its published basis. The runtime numbers are arithmetic on those figures under the assumptions stated, not measurements we made, and not a statement about whether any of this equipment is suitable for your therapy.