How to store a portable air conditioner, so it's ready next June

Why you shouldn't just wheel it into the closet

A portable air conditioner cools by pulling moisture out of the air, and not all of that water leaves through the hose. Some of it collects in a tray inside the unit and clings to the cold coil. Shut that away in a dark closet for nine months and you have ideal conditions for mold and mildew. You won't notice until the first hot day next year, when the unit blows a musty smell straight into your bedroom.

Storage is also where the small problems hide. A dusty filter hardens, a split exhaust hose gets worse, and the window kit loses a piece. None of it matters in October. All of it matters on the first properly hot day, when everyone else is also discovering that their unit doesn't work. The goal is simple: put it away clean, dry, complete, and upright.

The end-of-summer checklist for a portable AC

Pick a dry, mild day and work through these in order. The first two steps take the longest but need the least effort, so start them first and do the rest while the unit dries.

1. Drain the water. Unplug the unit and move it somewhere a little water won't matter, like a tiled floor or a balcony, with a shallow tray or towel under the drain port. Most portable units have a drain plug near the bottom at the back. Some have two: a higher outlet for continuous drainage and a lower plug for emptying the unit completely. Pull the lower one and let it run until it stops. Even “self-evaporating” models often hold more water than you'd expect.

2. Run it on fan-only to dry the inside. Put the plug back, switch the unit on, and run it in fan mode for a few hours. Use fan mode specifically, not cooling or dehumidify: those run the compressor and make fresh condensation. Fan mode just moves air across the coil, so the leftover moisture evaporates instead of sitting there all winter. If your model has a self-dry or self-clean program, it does exactly this. Afterwards, unplug it and drain it once more to catch the last drops.

3. Clean the filter. Slide out the air filter, vacuum off the dust, and rinse it in lukewarm water with a little mild soap if it feels greasy. Let it dry completely at room temperature, not on a radiator or in direct sun, before it goes back in. If your unit also has a carbon or fine-particle filter, those usually can't be washed. Note the part number now so you can order a replacement before next summer, not during it.

4. Wipe down the grilles and casing. With the unit unplugged, vacuum the intake and exhaust grilles with a soft brush attachment and wipe the housing with a slightly damp cloth. Don't spray water into the vents or poke at the metal fins behind them; they bend easily.

5. Check the exhaust hose and window kit. Detach the hose and look along its whole length for splits, holes, or crushed sections. A leaky hose pushes hot air straight back into the room, and it's the part most likely to fail next year. Make sure it's dry inside, then store it loosely coiled, never folded flat or squashed under something heavy. Clean the window adapter and slider panels and check that any foam seal strips aren't crumbling. Then bag every piece of the window kit together and keep the bag with the unit, because those pieces are always the first thing to go missing.

6. Inspect the power cord and plug. Look for cracks, kinks, scorch marks, or a plug that got warm in use. Many units sold in the US have a safety plug with Test and Reset buttons; press Test, then Reset, to confirm it still trips. Any damage means a repair or a replacement cord, not tape. Wrap the cord loosely on its hook or with a strap rather than tightly around the unit.

7. Take the batteries out of the remote. Batteries left in a remote for months are how contacts corrode. Put the remote in the same bag as the window kit so next summer you're not hunting for it.

8. Write down anything that wasn't right. Did it rattle, drip, show an error code, or struggle through the worst week of August? Deal with it now. Autumn is the quiet season for repairs and spare parts, and it's worth checking whether the unit is still under warranty before that runs out over the winter.

How to store it: upright, dry, and covered

Keep it upright. A portable air conditioner has a compressor with oil and refrigerant inside, and it's built to stand on its wheels. Store it and carry it upright. If it does end up on its side, say in the back of a car, stand it up and give the oil time to settle before switching it on. Your manual will say how long; if in doubt, wait a full 24 hours.

Pick a dry spot. A closet, spare room, storeroom, or the space under the stairs is ideal. Avoid damp basements and garden sheds, where humidity, mice, and insects all find their way in. If the only option is an unheated garage, check the storage temperature range in the manual first.

Cover it, but let it breathe. The original box is the best storage there is. If that's long gone, drape an old sheet or a breathable cover over the unit to keep dust out of the grilles. Don't seal it airtight in plastic wrap: if any moisture is still inside, plastic traps it there.

Nothing on top. Keep heavy boxes off the top panel and controls, and don't lean anything against the grilles.

Don't forget the rest of the summer gear

Fans. Unplug them, take off the front grille, and wash or wipe the blades and cage, then let everything dry. Slip a large bag or an old pillowcase over the fan head before it goes into storage. Dust you keep out now is dust you won't blow around the room next summer. Ceiling fans stay where they are, of course. For more on keeping all of these in shape through the year, see our air conditioner and fan maintenance guide.

Evaporative air coolers. These are the most mold-prone thing in the cupboard, because they're designed to be wet. Empty the water tank completely, rinse it, wipe it dry, and leave it open for a day. Let the cooling pads dry out fully and replace them if they're discolored or smell musty. Run the fan without water for a while to finish drying before you pack it away.

Next summer: waking it back up

When it's time to bring the unit out, spend five minutes before the first hot day. If it was moved, stand it upright where it will live and give it time to settle. Check that the filter is back in, reattach the hose and window kit, and run a short test.

Do that in May, not the afternoon the heat wave arrives. The first real heat has been showing up earlier in recent summers, as we cover in our seasonal cooling guide, and a problem you find in May is much easier to fix than one you find in July.

Storing a portable air conditioner: common questions

How do you prepare a portable air conditioner for winter storage? Drain the water through the bottom drain plug, run it on fan-only mode for a few hours to dry the inside, and drain again. Clean and fully dry the filter, check the exhaust hose and power cord, take the batteries out of the remote, and store it upright and covered in a dry place.

Do you need to drain it before storing it? Yes. Water left in the tray or on the coil grows mold and mildew over the winter, which you'll smell the first time you switch it on. Even self-evaporating models usually hold some water.

Can you store a portable air conditioner on its side? It's best not to. It contains a compressor with oil and refrigerant and is designed to stay upright. If it has been on its side, stand it upright before switching it on for as long as the manual says, or 24 hours if in doubt.

Where is the best place to store it? Somewhere dry and indoors, like a closet or spare room, ideally in the original box or under a breathable cover. Avoid damp basements, sheds, and airtight plastic wrap.

Why does my portable AC smell musty after storage? Usually because it was put away wet. Clean the filter, drain the unit, and run it on fan-only mode for a few hours. If the smell stays, the coil may need a proper cleaning.

Set it once with House Bober

Packing the AC away is a once-a-year job, which is exactly why half the steps get skipped and the unit gets forgotten until it's already too hot. The House Bober app is built for jobs like this. Add your portable AC, create a “pack away the AC” task that repeats every 12 months, and mark it done today. Next September it comes back as a reminder instead of an afterthought. You can also attach a photo and a note with the model number and filter part, so next year you know exactly what to order. It's the same idea behind our home maintenance schedule, applied to the gear you only think about twice a year.