What size battery do I need for a CPAP machine?
A CPAP machine without a heated humidifier uses little power, around 30 to 55 W, but for eight hours straight. We assume two nights without recharging. A humidifier can double the draw, so check the label on your machine and change the value.
A typical setup
These devices at these power levels, for 48 hours without recharging. Adjust them to yours with the button below.
| Device | W | Surge W | h/day | Wh/day |
|---|---|---|---|---|
| CPAP machine | 40 W | 90 W | 8 | 320 Wh |
| Phone | 15 W | 15 W | 2 | 30 Wh |
- 350 Wh
- 989 Wh
- 55 W
- 105 W
Estimates based on typical consumption. They include inverter losses and a 20% reserve.
Recommended for this typical use
No battery in stock meets every requirement according to its spec sheet. Try fewer days, no weight limit or a bigger budget.
Might work, but a figure is missing
They meet everything their spec sheet lists, but the manufacturer does not publish one of the figures we need. We do not count them as a match.
- Anker Solix F1500 1,536Wh / 1800W€520/kWh€799.00
Solar generators
1,536 Wh nominal for the 990 Wh you need (usable capacity not published)
Missing: continuous output and surge power.
- Anker Solix C2000 Gen 2 – 2048Wh/2400W Portable Power| A17832A1€585/kWh€1,199.00
Power stations
2,048 Wh nominal for the 990 Wh you need (usable capacity not published)
Missing: continuous output and surge power.
Sorted by price per usable kWh among those that meet everything. Retailer commissions play no part. How we rank
How we calculate it
For each device we multiply its power by the hours per day and by the share of time it actually runs (a fridge only runs its compressor part of the time). We add them up and multiply by the days without recharging.
We divide that total by the inverter efficiency, which we take as 85%, and add a 20% reserve for cold weather, cell wear and not draining the battery completely. We compare it with the usable capacity the manufacturer declares, or the nominal one if it does not publish it, and we flag that.
Continuous output is the sum of what runs at the same time. Kitchen appliances and tools count one at a time, the biggest one. Surge power adds what the device with the highest start-up demand draws when it switches on.
We do not recommend batteries with more than three times the capacity you need, because you would pay for and carry capacity you will not use. If a battery is missing a figure we need, such as surge or solar input, we do not count it as a match.
Typical power figures for 230 V household power.
This is not medical advice. Check with your CPAP manufacturer how to run it from a battery. Many offer a 12 V adapter that avoids inverter losses.