Choosing the right air conditioning unit

Step one: size the room correctly

Air conditioning capacity is measured in BTU (British Thermal Units) or kilowatts, and getting this wrong is the single most common mistake in DIY buying. An undersized unit runs constantly and never quite reaches temperature; an oversized unit cools too fast, switches off before properly dehumidifying the room, and short-cycles in a way that wastes electricity and shortens compressor life.

Sizing depends on room dimensions, but also on ceiling height, glazing, insulation, how many people typically use the space and any heat-generating equipment like servers or catering appliances. This is why a proper site survey beats an online calculator: a small glazed office facing south needs more cooling capacity than an equivalent north-facing room with smaller windows.

Step two: pick the unit type

Once you know the capacity needed, the next question is what shape of indoor unit suits the room. Wall-mounted units are the cheapest and quickest to fit and suit single rooms without a suspended ceiling. Ceiling cassettes give more even coverage in square or open-plan rooms and disappear almost entirely into the ceiling. Ducted systems hide everything above the ceiling and suit renovations or new builds where a completely clean finish matters.

For businesses needing several rooms covered, multi-split or VRF systems change the calculation again, because you're choosing a family of indoor units against one shared outdoor unit rather than sizing each room in isolation.

Step three: choose a brand sensibly

Panasonic, LG, Mitsubishi Electric and Midea are all well-established brands that we fit regularly, and each offers reliable equipment across residential and commercial ranges. Brand differences tend to matter more in warranty terms, parts availability and specific features like Wi-Fi control or quiet operating modes than in raw cooling performance, which is largely a function of correct sizing and installation quality regardless of badge.

Be wary of unusually cheap unbranded units sold online, since parts availability and warranty support can be poor, and an installer may be unable to service or guarantee a system built around an unfamiliar model.

Step four: decide on controls

Most units come with a basic infrared remote as standard, which is fine for a single room used by one household or one office. If you want app control, scheduling, or integration with a wider building management system, this needs specifying at quote stage since it can affect wiring and, on some models, the indoor unit chosen.

For commercial premises with several rooms, a wired controller or simple zoning setup is often worth the modest extra cost, since it lets staff adjust their own zone without affecting neighbouring rooms.

Step five: set a realistic budget

• Unit cost varies by capacity, brand and indoor unit type, with cassettes and ducted units typically costing more than wall-mounted equivalents of the same capacity.
• Installation cost depends on pipe run length, electrical supply work, and whether scaffolding or access equipment is needed for the outdoor unit.
• Ongoing costs include servicing, which is typically needed at least annually to maintain performance and warranty validity.
• As a guide, budgets should account for installation and commissioning, not just the unit price quoted online.

Getting a survey rather than a guess

Every one of these five steps benefits from a proper site visit rather than online sizing tools and brand comparisons alone. A surveyor can check ceiling void depth, electrical supply capacity, and pipe run distance before recommending a specific unit type and capacity, all of which shape the final price far more than brand choice does.

If you'd like a straightforward, no-obligation quote for your home or business, get in touch and we'll arrange a site visit to work through these decisions with you.