Does a CPAP need a pure sine wave inverter?
Use pure sine wave. CPAP manufacturers specify it, and essentially every current portable power station provides it. Modified sine wave can cause audible buzzing, heat in the power supply, and sometimes a machine that refuses to start — not a risk worth taking on equipment you rely on nightly.
Mains electricity is a smooth sine wave. A cheap inverter approximates it with a blocky stepped waveform — "modified sine wave" — which is adequate for a kettle and much less adequate for sensitive electronics.
A CPAP uses a switching power supply, and those are among the most waveform-sensitive things in the house.
What modified sine wave does to a CPAP
The common symptoms are a buzzing or whining noise from the power brick, the brick running noticeably hotter than on mains, erratic behaviour from the humidifier's heating control, and occasionally a machine that simply will not power on.
None of these are guaranteed, and plenty of people report running a CPAP on modified sine wave without incident. But "it usually works" is a poor standard for a device treating a condition that interrupts your breathing.
Manufacturers are unambiguous — ResMed and others specify pure sine wave in their own documentation. Check the wording in your machine's manual for the model you own.
The good news: largely a solved problem
Essentially every current portable power station from the mainstream brands — Jackery, EcoFlow, Bluetti, Anker — outputs pure sine wave and says so on the spec sheet. Buying new from a known brand, you will almost certainly get it.
Where modified sine wave still turns up is in cheap cigarette-lighter inverters and in older or no-name units. Those are the ones to avoid for this job.
| Power source | Typical output | Suitable for CPAP |
|---|---|---|
| Current-generation power stations | Pure sine wave | Yes |
| Dedicated CPAP batteries (DC) | No inverter at all | Yes — best case |
| Cheap cigarette-lighter inverters | Modified sine wave | Avoid |
| Older or no-brand inverters | Often modified | Check before use |
How to check what you have
Look for the phrase "pure sine wave" in the AC output section of the spec sheet. If a listing does not say it, assume it is modified — manufacturers advertise pure sine wave when they have it, because it costs more to build.
If you cannot confirm, running the machine on DC instead sidesteps the question completely, since no inverter is involved. That route also gains runtime — see DC vs AC.
- Will modified sine wave damage a CPAP?
- It may not damage it outright, but it commonly causes buzzing, excess heat in the power supply, and sometimes a refusal to start. Manufacturers specify pure sine wave, so use it.
- Do Jackery and EcoFlow power stations output pure sine wave?
- Current models from the major brands do and list it in their specifications. Confirm on the spec sheet for the exact model rather than assuming across a product line.
- Does running on DC avoid the issue?
- Yes. On DC there is no inverter and so no waveform to worry about, which is one reason dedicated CPAP batteries run DC to DC.
Keep reading
Keep reading
- Should you run a CPAP on DC or AC from a battery?
Run it on DC if your machine supports it.
- CPAP battery or portable power station — which should you buy?
Buy a dedicated CPAP battery if the only job is the CPAP and you travel with it: DC-native, lighter, and sub-100Wh models are the simplest category to fly with.
- How long will a power station run a CPAP?
A 1,000Wh power station runs a typical CPAP for about 98 hours — roughly 12 nights — with the humidifier off.
- Does the CPAP humidifier drain the battery?
Yes — dramatically.