Start with the two calls that matter more than any equipment
Ready.gov's guidance is explicit: "Talk to your medical provider about a power outage plan for medical devices powered by electricity and refrigerated medicines." That conversation establishes what your specific therapy actually tolerates, and no page on the internet can substitute for it.
The second call is to your electric utility. Many run a registry for customers who depend on electrically powered medical equipment. Being on it does not guarantee faster restoration, but it puts you in the notification and priority processes that exist. Ask what your utility calls its program.
Ready.gov also says to "find out how long medication can be stored at higher temperatures and get specific guidance for any medications that are critical for life." Do that before you buy anything.
What medical devices actually draw
| Device | Published draw | Duty | Per 24 hours |
|---|
| CPAP, humidifier off | 30–60 W | ~8 hrs | ~240–480 Wh |
|---|
| CPAP with heated humidifier | 60–100 W+ | ~8 hrs | ~500–800 Wh |
|---|
| Oxygen concentrator, 5 LPM (EverFlo) | 350 W | Continuous | ~8,400 Wh |
|---|
| Oxygen concentrator, efficient at 2 LPM | ~100 W | Continuous | ~2,400 Wh |
|---|
| Nebulizer | ~100–200 W | ~15 min per treatment | ~100 Wh |
|---|
| Small fridge for medication | ~60–80 W cycling | ~30% duty | ~500–600 Wh |
|---|
CPAP figures from Champion Power Equipment's published wattage chart. The 350W and ~100W concentrator figures are the published consumption for the Philips Respironics EverFlo at 5 LPM and for an efficient stationary unit at 2 LPM. Nebulizer and fridge rows are working estimates from typical equipment ratings, not measurements. Your device's own label is the figure that counts.
The table makes the point on its own. A CPAP is a small, intermittent load that a modest battery covers easily. A stationary oxygen concentrator running continuously at 350W needs about 8.4kWh a day — four times what the largest battery on this site holds.
What that means for oxygen specifically
Be blunt about the arithmetic, because this is the case where optimism is dangerous.
- 2,048Wh at 350W is roughly five hours after inverter losses. Useful, not a night.
- An overnight run needs about 3kWh, which means an expandable battery with a second pack, or a generator.
- Days need fuel. A generator is the only portable answer, with a battery indoors as the buffer that lets the engine run in blocks rather than continuously.
- Cylinders are the real backup. Ask your equipment supplier about backup oxygen cylinders. They need no power at all, and for many people they are the correct answer rather than a bigger battery.
If oxygen is the load, treat any battery you buy as the bridge that gets you to a generator, a cylinder, or somewhere with power — not as the plan itself.
Refrigerated medication
Two separate pieces of published guidance apply, and they are worth reading carefully because they point in different directions.
Ready.gov: "If the power is out for more than a day, discard any medication that should be refrigerated, unless the drug's label says otherwise." That is the conservative default for medication generally.
FDA's insulin-specific emergency guidance is more permissive, and explicitly written for this situation: insulin in manufacturer vials or cartridges, opened or unopened, "may be left unrefrigerated at a temperature between 59°F and 86°F for up to 28 days and continue to work."
The rest of the FDA guidance matters as much as that headline:
- Effectiveness falls with exposure to extreme temperatures, and the longer the exposure the greater the loss.
- Insulin altered by dilution or removed from the manufacturer's vial should be discarded within two weeks.
- Insulin in a pump infusion set should be discarded after 48 hours, or if exposed above 98.6°F.
- Once properly stored insulin is available again, vials exposed to extreme conditions should be discarded and replaced.
Practically: for insulin, an outage of a day or two in a temperate house is covered by the FDA window without any equipment. What a battery buys is the summer case, where an unpowered house exceeds 86°F, and the general case of medications that have no equivalent guidance. Ready.gov also notes a closed refrigerator holds temperature for about four hours and a full freezer for about 48 — keep the door shut.
The arrangement that works
For most households with one electrically powered medical device, this is the shape of it:
- A battery indoors, always charged. Silent, no exhaust, clean sine wave, and safe in a bedroom — the only thing that can sit beside a sleeping person.
- A generator outdoors if outages run long, at least twenty feet from the house with exhaust pointed away, used in blocks to refill the battery rather than to power the device directly.
- Solar input if you are in a storm region. A folding panel turns a fixed capacity into a daily allowance, which is the difference between three days and indefinite.
- A non-electric fallback — cylinders, a cooler and ice, a plan to relocate. Equipment fails; a plan with a second branch does not.
Size the battery to the device and the hours you actually need, not to a headline capacity. Matching capacity to outage length and the home backup comparison both work through the numbers.
Two safety points that are not negotiable
Never run a generator indoors, in a garage, or near a window. Twenty feet minimum, exhaust pointed away. Someone dependent on a medical device is often the person least able to detect or escape carbon monoxide, which makes a working CO alarm more important in this household than in any other, not less.
Test the whole chain before you need it. Plug the actual device into the actual battery and run it for an hour. Some medical equipment is fussy about waveform, some draws more than its label suggests, and the time to discover that is a Tuesday afternoon, not 3am in a storm.
