Power station for a CPAP: what size runs it through the night?

A night through the sizing formula

We use the existing 45 W CPAP and 80 W CPAP-plus-heat examples from PowerStation Size. Neither is a rating for every machine or for the ResMed and Philips accessories discussed below. The eight-hour night is an illustrative schedule. Actual consumption depends on your equipment and configuration.

For this page’s table, a night means 8 hours of use. We apply 85% inverter efficiency, 20% unused reserve and omitted inverter idle draw. Those are editable assumptions, not measurements of your station. Capacity is rounded upward to whole watt-hours. The table assumes no recharge between nights and no additional devices.

Without heat, the arithmetic is 45 W × 8 h = 360 Wh; 360 ÷ 0.85 ÷ 0.80 ≈ 530 Wh nameplate. With heat, it is 80 W × 8 h = 640 Wh; 640 ÷ 0.85 ÷ 0.80 ≈ 942 Wh nameplate. That difference is why the heat configuration must remain visible in a battery plan.

These figures are capacity targets, not device approvals. They do not establish whether an outlet remains on through light loads, whether a converter is compatible, or whether the system tolerates a power interruption. Use the general sizing guide for the distinction between energy, running power and startup checks.

Humidifier and heated tubing change the load

ResMed’s battery guide separates configurations by device, humidifier use, tubing and pressure setting. A blower-only figure should not be carried over to a setup using heated accessories. The heat example here is not a separately verified allowance for every humidifier and tube combination, so do not add or subtract an invented heater wattage.

If you want a lower-energy battery configuration, ask your clinician or equipment supplier whether changing humidifier or heated-tube settings is appropriate for you and how the device should be configured. Do not alter prescribed therapy settings to make a battery result fit. A reduction that is acceptable for another user is not a recommendation for your treatment.

Keep separate notes for the configuration you normally use and any alternative agreed with your provider. Label the saved calculator plan clearly. A result made with heat omitted becomes misleading if the accessories are enabled when you travel. Recheck the power arrangement after a machine, adapter or accessory changes.

AC and DC: compare the complete power path

An AC connection runs the machine through its mains supply and the station’s inverter. A compatible DC route can avoid that inverter stage, but a converter still has losses and limits. ResMed’s battery guide recommends its appropriate DC-to-DC converter rather than an inverter for the devices covered by that guide. The document is older; confirm current compatibility for your exact equipment. It addresses stand-alone deep-cycle batteries with daily recharging, not validation of our multi-night power-station examples.

ResMed’s UK AirSense 11 converter page describes an accessory for that device using a suitable 12 V or 24 V vehicle auxiliary supply, including configurations with its named humidifier and heated tube. This verifies that specific accessory’s intended use. It does not certify every portable station’s DC port or a generic cable.

Philips’ DreamStation DC-cord sheet describes a 12 V cord and compatible battery connection, including connected heated accessories. That is an older product document, not evidence of compatibility with every later Philips device. Ask the supplier to match the exact model, current instructions, connector and electrical requirements.

Do not turn the AC table into a DC promise by deleting the efficiency allowance. Our calculator uses an AC-oriented planning model; it has no verified conversion-loss figure for your particular DC chain. The conservative next step is to obtain maker-specific consumption and compatibility information, not to assume loss-free operation because the connector fits.

Read the supply, then measure your own use

Look for the equipment model and electrical ratings on the power-supply label and in the manual. Distinguish the supply’s input requirements from its output rating. A supply rating describes the equipment it can support; it is not proof that the same power is drawn steadily throughout a night. Keep the label information for compatibility checks while establishing actual energy separately.

The North Dakota State University energy worksheet identifies labels and plug-in electricity monitors as ways to investigate appliance energy use. If your equipment provider permits it, a suitable plug-in energy meter on the AC supply can record total energy over your normal overnight session. Follow the meter and device instructions, and keep your prescribed configuration unchanged.

Record the session duration, measured energy and accessories used. Use energy divided by time to obtain an average input load for an illustrative plan, while retaining the real output and startup requirements for compatibility. A measurement under one set of conditions does not prove future runtime; repeat or confirm the assessment when the setup changes.

Outages and camping across several nights

The figures below extend exactly the same assumptions. They are our calculations, not a maker’s measured runtime table. Click a result to inspect the assumptions. Do not round the nightly target first and multiply it: the calculation rounds the final total upward.

For an outage, also plan what happens if the grid stays unavailable or the backup fails. For camping, establish the intended recharge arrangement before leaving. Neither a campsite socket nor useful sunshine should be assumed without checking. Phones, lights and other loads must be added to the list rather than silently sharing the medical-device allowance.

Wall, car and solar recharging

Use the station’s specified wall charger when mains power is available. Confirm the available socket and charging instructions before travel, and follow the manual’s conditions for charging or powering loads at the same time. A fast-charge claim for the station does not establish anything about therapy continuity.

For vehicle charging, check the station’s permitted input and the vehicle outlet’s limits. Charging the station from a vehicle is different from powering a CPAP directly through a maker-approved converter. Do not assume a vehicle starting battery can support an overnight load without consequences. ResMed’s battery guide warns about vehicle-battery discharge and voltage spikes when starting an engine; follow current instructions for your arrangement.

Solar recharge depends on compatible panels, input limits, weather, positioning and time available. The calculator exposes panel and sunlight assumptions separately from stored capacity. No local harvest, guaranteed recharge time or promised camping-night total is invented here.

Use product cards as a comparison starting point

Small-to-mid examples appear below using the existing maker-sourced comparison. The compact base models shown do not cover even the no-heat night under this article’s AC assumptions. They remain visible to explain the shortfall, not as CPAP recommendations. A larger energy rating still cannot approve an adapter or provide a medical-backup guarantee.

Match the checked region and look at each missing specification. Our model checks compare entered energy and watts on paper, while non-fridge startup inputs remain unverified placeholders until replaced. Ask the equipment provider about the complete system and interruption requirements before treating any station as part of your backup plan.

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