Short AC hose run beside UK window

Keep Hose Runs Under 2m: Portable AC Hose Length for UK Homes

Most portable air conditioners ship with a hose that compresses to around 1.2 to 1.5 metres and stretches to roughly 1.5 to 2 metres at full extension, according to DIY Doctor’s guide to portable air conditioners. The practical rule is simple: keep the installed run as short and straight as you can, because every extra bend or metre of hose reduces airflow and cooling power. Diameter and routing matter more than a few centimetres of extra length.

TL;DR:

  • Extending a portable AC hose beyond 2 meters causes significant airflow resistance, reducing cooling efficiency and increasing compressor strain.
  • Most hoses ship compressed to roughly 1.2 to 1.5 meters and stretch up to 1.5 to 2 meters; exceeding this length worsens performance.
  • Proper routing with minimal bends, supports, and straight lines is crucial to prevent kinking, condensation pooling, and airflow restrictions.
  • Match the hose diameter precisely to the spigot size, typically between 100 mm and 150 mm, to ensure an airtight seal and optimal airflow.
  • When longer runs are necessary, use smooth, short extensions and avoid multiple jointed sections, or reposition the AC closer to the window for better performance.
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Table of Contents

What the numbers mean: compressed length, stretched length and diameter

Manufacturers usually quote two figures for a portable AC hose. The compressed length is the hose in its coiled, neutral state, before you pull it out. The stretched or maximum length is how far it extends when fully pulled, and this is the figure most buyers focus on when checking whether a unit will reach their window.

Diameter matters just as much as length. Most domestic units use a spigot in the 100 to 200 millimetre range, which is roughly 4 to 8 inches, and the hose has to match that spigot exactly or you lose airflow through gaps at the joint, as installation discussions on DIY Doctor’s forum point out when explaining why the wrong grommet or adaptor causes fitting problems. A hose that is technically long enough but the wrong diameter will still perform poorly.

A few numbers worth keeping in mind when comparing specifications:

  • Compressed length is typically quoted as roughly 1.2 to 1.5 metres, per DIY Doctor.
  • Stretched or maximum length usually sits around 1.5 to 2 metres for domestic portable units.
  • Common spigot diameters run from 100 mm (about 4 inches) to 150 mm (about 6 inches), with some larger units up to 200 mm (about 8 inches).
  • Single-hose and twin-hose units vent differently, which changes how the hose length interacts with room air pressure, as DIY Doctor explains.

Advertised length is not always usable length. Some listings quote the stretched maximum, which looks generous on paper but performs worse once you factor in bends near the window kit.

Practical measurement and installation checklist for the hose run

Get the measurement right before you buy anything, and the fit problems mostly disappear. Start by measuring the straight-line distance from the AC unit’s spigot to the window or wall vent point, then walk that same route with a tape measure to capture the actual path the hose will follow, including any furniture or door frames it needs to clear.

Add extra length for every bend the hose has to make. A single gentle curve barely affects the total, but each additional turn should add a small allowance, typically 10 to 15 centimetres, so the hose is not stretched taut at the joints. Taut hoses pull on the spigot and the window kit fitting, which weakens the seal over time.

Follow this sequence on site:

  1. Measure the straight-line distance from spigot to vent point.
  2. Trace the planned route and note every bend or obstruction.
  3. Add 10 to 15 centimetres per bend as slack allowance.
  4. Account for window kit thickness and spigot depth, both of which eat into usable length.
  5. Mark the final route with a spirit level to check the hose will not sag or pool.
  6. Fit supports or clips every so often along longer runs to stop the hose drooping under its own weight.

Keep a small kit handy: a tape measure, a marker pen, a spirit level, and a few cable clips or hose supports. These are cheap and solve most fitting headaches before they start. For a worked example of the whole process, Simco Direct’s guide on venting a portable AC through a window kit walks through the fitting steps with photos.

Pro Tip: Dry-fit the hose and window kit before switching the unit on, so you can adjust the route while the room is still cool and you are not rushing.

Extending the hose: safe methods, performance trade-offs and practical limits

Lengthening a portable AC hose is possible, but it comes at a real cost to performance. Every extra metre increases resistance to airflow, which forces the compressor to work harder and can lead to warm air being pulled back into the room, a problem known as reheat.

If you do need to extend, stick to a few basics:

  • Use short, smooth duct extensions rather than several flexible sections joined together.
  • Choose proper adaptor couplings sized to match the existing hose diameter exactly.
  • Avoid joining more than one extension piece, since each seam is a potential air leak and a spot for turbulence.
  • Treat 2 metres as a sensible practical ceiling for most domestic units, beyond which cooling drops noticeably.

Community discussion on DIY Doctor’s forum repeatedly comes back to this kind of short, practical threshold: once a run needs meaningfully more hose than the unit ships with, the fix is usually to reposition the AC closer to the window, not to keep adding hose sections.

Typical installation errors that reduce cooling or damage the hose

Most performance complaints trace back to a handful of avoidable mistakes rather than a faulty unit.

  • Kinking or sharp bends: tight bends restrict airflow far more than length does. Manufacturers advise keeping the hose as straight as possible, and forum reports confirm that S-shaped routing is common but discouraged because it increases back pressure.
  • Multiple bends stacked together: one gentle curve is fine; two or three tight turns in sequence noticeably cut cooling output and can let warm exhaust air drift back into the room.
  • Condensation pooling: a hose that dips in the middle collects moisture, which can drip back towards the unit or block airflow. Route the hose so it slopes gently towards the window, not the appliance.
  • Unsupported long runs: a hose left to sag under its own weight vibrates against furniture or walls, causing noise and wear. Support it every metre or so with a simple clip or bracket.
  • Modifying hoses without checking warranty terms: cutting, taping or forcing an ill-fitting adaptor onto a hose can void the manufacturer’s warranty, so check the terms before altering anything.

Pro Tip: If you hear a new rattling noise after fitting a longer hose, it is almost always a support issue rather than a fault with the unit itself.

Simco Direct practical guidance and where to find compatible parts or kit help

Getting the fit right the first time saves a return trip to the shop. Before buying a replacement hose or window kit, check the spigot diameter stamped on your existing unit and match it against the new part rather than assuming a universal fit.

  • Simco Direct’s guide on venting a portable AC with a window kit covers the fitting steps with photos for a typical window kit install.
  • Always confirm spigot diameter against the hose or adaptor before ordering, since a mismatch is the most common fitting complaint.
  • If you are choosing between a single-hose and dual-hose setup, our piece on single-hose versus dual-hose AC units explains how that choice affects hose routing.
  • Accessory purchases often include a returns policy for flexibility if a hose or kit does not fit as expected.

Reach out to Simco Direct’s customer support team if you are unsure which spigot size or kit your unit needs before placing an order.

Choosing between adapting your installation and replacing the unit

Choosing between adapting your installation and replacing the unit — overview diagram

My view is that most hose problems are routing problems, not length problems. If your required run is close to the hose’s stretched maximum, a single sensible bend and good support will usually solve it. Once the run genuinely needs more than that, adding extension pieces rarely pays off in comfort, and repositioning the unit or picking a different cooling option is the better fix.

Renters in particular should favour a temporary window kit over anything permanent, since it can be removed cleanly at the end of a tenancy. Whatever you choose, run the unit for twenty minutes after fitting and check the room actually cools. That simple test tells you more than any spec sheet.

— Carl

Where to buy hoses, window kits and accessories

Simcodirect

If your existing hose or window kit needs replacing, Simco Direct stocks the accessories to fix a fitting problem without a full unit swap, backed by fast delivery and a 30-day returns policy on accessories. Browse our window kit installation guide for fitting steps, or head to the Simco Direct shop to check stock on hoses, kits and related heating and air treatment products. If you are not sure which spigot size or kit suits your unit, get in touch with our support team before you order.

Sources

FAQ

How long can my portable AC hose be?

Most units ship with a hose that compresses to around 1.2 to 1.5 metres and stretches to about 1.5 to 2 metres at full extension, according to DIY Doctor. Beyond that stretched maximum, cooling performance drops noticeably, so it is best treated as a practical ceiling rather than a target to reach.

Can I get a longer hose for my portable air conditioner?

Yes, but extending it reduces airflow and increases strain on the compressor, so it should be done with a single smooth extension piece rather than several joined sections. Matching the diameter exactly to your existing hose matters more than the extra length itself.

What causes reduced cooling when the hose is bent?

Tight bends and S-shaped routing increase resistance to airflow, which is why manufacturers advise keeping the hose as straight as possible, a point confirmed by installation reports on DIY Doctor’s forum. Multiple bends stacked together make the problem worse than any single gentle curve.

What size spigot do portable AC hoses use?

Common spigot sizes range from 100 mm to 200 mm, roughly 4 to 8 inches, depending on the unit, with installation discussions noting 150 mm as a frequently used size for flexible ducting. Always check the diameter on your own unit before ordering a replacement hose or adaptor, since a mismatch is the most common cause of poor fit.

Does the type of portable AC affect hose length needs?

Single-hose and twin-hose units vent differently, which changes how sensitive each is to hose length and routing, as explained in our comparison of single-hose and dual-hose AC units. In general, keeping the run as short and straight as possible benefits both types.

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