Air Conditioning Without an Outdoor Unit: Through-Wall Monobloc Units

Fixed air conditioning normally means a box on the outside wall. But there is a category of unit that keeps every working part indoors and vents through the wall instead: the through-wall monobloc. A monobloc or single-packaged model "has only one indoor unit and no outdoor unit", with the refrigerant liquid and the main components such as the evaporator and compressor all contained in that one unit, expelling hot air via a duct¹. Energy Saving Trust describes the same idea as an all-in-one system where "it doesn't need any outside unit at all, all components are in a single indoor unit"².

That single difference changes who can have fixed air conditioning at all. If you live in a flat with no exterior wall rights, a listed building, a conservation area or a house where the freeholder or planners will not allow an external condenser, a through-wall unit is often the only route to real, fixed cooling rather than a portable air conditioner trailing its hose to a window. This page explains the designs, the Powrmatic Vision range sold in the UK, what the installation involves, where planning permission stands in England and Scotland, and what these units cost.

Types of system with no external component explained

"No outdoor unit" is used loosely in the market, and it covers three quite different designs, so it is worth being precise about which one you are buying.

The first is the true monobloc. As Netatmo's guidance puts it, "A monobloc or single-packaged model has only one indoor unit and no outdoor unit. The refrigerant liquid as well as the main components (evaporator, compressor etc.)" sit inside that unit, with hot air expelled through a duct¹. Because the refrigerant circuit is sealed inside the casing at the factory, there is no refrigerant pipework to be run and jointed in your home, which is the main reason these units can be fitted without the same refrigerant handling as a split system.

The second is the through-wall twin duct unit, the design this page is mostly about. These are fixed monoblocs that mount through an exterior wall. "These units, known as 'Twin Duct,' require three holes for installation. One hole, small in size, releases the unit's ge" nerated condensate, and two larger ducts handle the exchange of cool and hot air³. The unit stays indoors; only the vent grilles show outside.

The third is the portable monobloc, which shares the same sealed-circuit idea but rolls from room to room on castors. Portables are "convenient because it can be moved around the house", can be stored away when not in use, and need no fitting work at all¹. The trade-off is performance and noise, which is why the fixed through-wall design exists: it gives you monobloc simplicity with a permanent, properly vented installation.

The appeal of indoor-only air conditioning for households

The reasons are usually practical rather than preferential. Energy Saving Trust notes that "The monobloc system could be suitable for homes where external installation is challenging due to limited access or plan" ning restrictions². That covers a large slice of UK housing: flats above ground level with no accessible wall, homes in conservation areas, listed buildings, and leasehold properties where the exterior is common parts controlled by the freeholder or management company. Our page on air conditioning in flats goes into the lease and consent side of that.

The second reason is installation simplicity. With no outdoor condenser there is no scaffold or ladder work at height, no refrigerant pipe runs between indoor and outdoor units, and no condensate pump lifting water outdoors. The maker describes the Powrmatic Vision 3.1 DW as offering a "Simple, drill-and-fix setup with no need for an outdoor condenser"³, and the Vision Compact 2.3 DW as "a slim, space-saving unit with no external condenser required"⁴.

The third reason is future flexibility. An air-to-air heat pump of this kind "doesn't need underfloor heating or radiators"⁸, so a through-wall unit can be added to a home without touching the existing wet heating system, and removed again without leaving one behind. That matters in rented homes and in conservation properties where wet-system alterations are their own consent battle.

What you give up is capacity and, usually, some efficiency. Sealing everything in one casing constrains the heat exchangers, and venting through wall ducts rather than a large outdoor condenser costs performance. For a single room, that trade is often acceptable. For a whole house, a multi-split system with one outdoor unit serving several rooms will usually do more with less electricity.

The Powrmatic Vision range: models, prices and what each suits

Powrmatic is the brand most visible in the UK through-wall market, and its Vision range covers several mounting styles. All share the self-contained principle: the Vision Maxi DW is described as "A fully self-contained system, eliminating the need for an outdoor unit"⁴, and the range as a whole is listed as "fully self-contained with no need for an outdoor condenser"⁴.

Two cautions on these figures. The prices above are the maker's listed prices excluding VAT, and the same models appear at different figures on different pages: the Vision 3.1 DW is listed at £2,299.99 including VAT (£1,916.66 excluding VAT) on one page and £1,695.01 including VAT (£1,412.51 excluding VAT) on another, and the Compact 2.3 DW appears at both £2,103.99 including VAT (£1,753.33 excluding VAT) and £1,374.01 including VAT (£1,145.01 excluding VAT)⁴. High street prices run higher still: the 3.1 DW is shown at £3,995.00 and the 3.1 DW/H at £3,734.17 excluding VAT⁴. Treat every figure as a list price to be quoted against, not a street price.

Noise figures for the Vision range are not published in the material here, so if noise matters, and in a bedroom it usually does, the measured figure for the exact model is something to ask the installer for in writing. Our page on air conditioning noise explains what these numbers mean in practice.

Sizing cooling output to suit your space

The Vision range sits firmly in single-room territory. The Vision Maxi DW carries a listed cooling capacity of 3.5 / 1.05 kW Dual Power Max/Min⁴. For context, one Daikin multi-split outdoor unit in the same market covers a cooling capacity of 5.2 to 9.0 kW across several indoor units⁹: that is the scale of system needed once you move beyond one or two rooms.

A smaller unit suits a small bedroom or study; the Maxi, at 3.5 kW maximum cooling capacity⁴, suits a medium living room or a conservatory-style space with high heat gain. But the nominal figure is only the starting point. Room size, glazing, insulation, ceiling height and the direction the room faces all shift the requirement, and an undersized unit will run constantly without reaching temperature. Our air conditioning sizing page explains the kW and BTU figures in full, and the comparison between smaller and mid-size single-room units shows how the step up plays out in a real room.

One structural limit is worth stating plainly: a through-wall monobloc cools the room it sits in. There is no outdoor unit to serve additional indoor heads, so cooling several rooms means either several through-wall units or a different design. If your need is a whole flat or house, read our page on types of air conditioning before committing to this route.

How efficiency ratings translate into bills

Because a monobloc moves heat rather than generating it, the running cost is a fraction of an electric heater's for the same room. The Centre for Sustainable Energy models cooling with a system "operating at a Coefficient of Performance (COP) of 3.5 (i.e. 1 kWh electricity gives 3.5 kWh cooling)"⁵. At that performance, every unit of electricity bought from the grid delivers three and a half units of cooling into the room.

The COP is the number to look at, and the same logic runs in reverse when the unit heats. A heating COP of around 3 means roughly three units of warmth per unit of electricity, against exactly one from a resistive heater. Our page on air conditioner versus electric heater efficiency works through the sums, and air conditioning running costs gives per-hour figures.

Against a split system, a through-wall monobloc will usually give up some efficiency, because the condenser heat exchange happens through wall ducts rather than a freely ventilated outdoor coil. The maker does not publish comparative efficiency figures for the Vision range in the material here, so any efficiency claim made at the point of sale is a figure to ask for in writing, on the specific model's energy label. Our page on efficiency ratings explains the EER, SEER and SCOP labels shown on those labels.

Fitting the unit: drilling the wall opening and routing services

Fitting is the defining feature of these units. The maker describes the Vision 3.1 DW as a "Simple, drill-and-fix setup with no need for an outdoor condenser" and the Compact 2.3 DW as a "Simple, hassle-free setup with a drill-and-fix system, requiring no external pipework"³.

The wall penetration is the part to understand before you commit. The twin duct design "require[s] three holes for installation. One hole, small in size, releases the unit's ge" nerated condensate, and "two larger ducts for exchange of cool and hot air" pass through the exterior wall³. So the outside of your wall ends up with vent grilles rather than a condenser box, and the inside gains a wall-mounted or floor-standing unit. The Vision Horizontal 3.1DW reduces this to a design that "installs through the wall with only two external vents"³.

What this means practically:

• The wall must be an exterior wall you can drill through, of a thickness the unit's ducts can span.
• The drilling is one-off structural work: once cut, the holes are permanent even if the unit is later removed.
• There is no refrigerant circuit to be broken into on site, which is why these units sit at the easier end of our DIY air conditioning installation page, though electrical connection still needs a competent person.
• In a listed building or a wall of traditional construction, drilling two or three cores is an alteration the conservation officer will want to know about, whatever the planning position on the unit itself.

Heating plus cooling in one unit reshapes usage and consent

Several Vision models are reverse-cycle: the Compact 2.3 DW is described as offering "powerful heating and cooling in a slim, space-saving unit"⁴, and the 3.1 DW/H carries the heating designation in its name. Energy Saving Trust confirms the general principle: air-to-air heat pumps "can be configured for cooling as well as heating"².

This matters twice over. First, for use: a heating-capable through-wall unit is not just a summer appliance but a supplementary heat source for the room it serves, running at heat-pump efficiency rather than resistive efficiency. Second, for planning: as the next section sets out, the permitted development rights for air conditioning in England apply only where the system provides a heating function⁷. A cooling-only through-wall unit and a heating-and-cooling unit of identical appearance can sit on opposite sides of that line.

It is worth being clear about what "no outdoor unit" means across the wider heat pump market, because the word monobloc is used there too. The NIBE S735-7 heat pump is listed with "No outdoor unit required"¹⁰, while the Ideal Logic Air heat pump is described as an "Outdoor monobloc unit"¹¹: in heat pump language, monobloc often means a single outdoor box with all refrigerant components, the opposite of a through-wall unit. Which side of the wall the single box sits on is the thing to establish before comparing products. Our page on air conditioning that heats covers reverse-cycle units in full.

Consent rules in England and Scotland

In England, the starting position is that "Adding air conditioning to your home may be considered permitted development provided all the limits and conditions set" out in the legislation are met, with limits covering the function, size, placement and quantity of units⁷. The critical condition for this page is the heating one: "The rights only apply if the system provides a heating function (including if it can provide both heating and cooling)." A cooling-only unit, however small or discreet, needs a planning application⁷.

Protected areas are the second gate. "If your home is in a protected area such as a Conservation Area then permission will be required. If you live in a liste" d building, listed building consent is required⁷. Cotswold District Council, an authority with extensive conservation stock, takes the same line on internal work generally: internal wall insulation is "Not development (planning permission not required)" except where permitted development rights have been removed or the home is in a conservation area or Area of Outstanding Natural Beauty¹², and the Scottish guidance on traditional buildings notes that "Planning permission is usually not required, although both planning and listed building consent may be required in some" situations¹³. A through-wall unit is not purely internal, because the ducts pierce the external wall, so the conservation and listed building questions apply to the wall penetration itself.

Where a system qualifies as an air source heat pump, the legislation adds conditions. In England and Wales, "Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards or equi" valent standards¹⁴. In Scotland, the equivalent regime sits in the Town and Country Planning (General Permitted Development) (Scotland) Order 1992 as amended: "Development which does not meet the criteria or thresholds within the legislation will not be considered to be permitted" development and requires a planning application¹⁵, and one explicit limit is that development "is not permitted if it would result in the presence on the same building or within the curtilage of a building of more than one air sour" ce heat pump¹⁶. Scottish reforms to permitted development for air source heat pumps have been taken forward through an amendment to that 1992 Order¹⁷.

Two final distinctions. Planning permission and building regulations are different regimes: work can comply with one and not the other, and "planning permission may not be" needed when building regulations approval is¹⁸. And none of this is legal advice on your particular property: a flat with a lease, a house with an Article 4 direction and a listed cottage each need their own check. Our nation pages on planning permission in England and Scotland carry the detail.

Prices, and the 0% VAT cut-off date

The purchase price of a through-wall unit spans a wide band depending on model and where you buy. Within the Vision range, the listed prices excluding VAT run from £1,753.33 for the Compact 2.3 DW through £1,916.66 for the 3.1 DW and £2,058.33 for the 3.1 DW/H, up to the Maxi DW, which carries a High Street price of £4,094.00⁴. Those are list prices for the unit: installation, electrical work and any making-good of the wall are quoted separately by the installer, and our air conditioning cost page sets out the full installed picture.

The VAT position is time-limited and worth acting on with open eyes. The legislation states: "This rate will apply from 1st February 2024 to 31st March 2027."⁶ That is the temporary zero rate of VAT on the installation of energy-saving materials. In Northern Ireland, the instrument "introduces a temporary zero rate of VAT for the installation of qualifying ESMs in residential accommodation" running from 1 May 2023 to 31 March 2027¹⁹. Ofgem's Boiler Upgrade Scheme guidance confirms the same window from the buyer's side: "between 1 April 2022 and 31 March 2027, there is a zero rate of VAT1 on the installation of energy-saving materials incl" uding heat pumps²⁰.

Through-wall units and how far they free you from constraints

A through-wall monobloc buys a household one clear thing: cooling, and in the heating variants heating too, without depending on anyone's permission for an outdoor box, a freeholder's consent for a façade, or access equipment for an external wall. It is the design that makes fixed air conditioning possible in homes where a split system is simply not available, and because it needs no radiators or underfloor heating⁸, it slots alongside whatever heating arrangement a home already has.

The dependencies that remain are the honest part of the picture. The unit runs on grid electricity, so its running cost moves with the price cap and with your supplier's tariff; the CSE's modelling of cooling costs at a COP of 3.5⁵ is only as stable as the electricity price behind it. The refrigerant circuit is sealed at the factory, so unlike a split system there are no on-site refrigerant joints, but the unit's life still depends on the manufacturer's company and its spare parts, and on an installer for anything beyond filter cleaning. And the wall holes are permanent: the unit can be taken down, but the ducts leave a trace.

Set against that, a heating-capable through-wall unit is one of the few appliances that reduces a household's exposure in both directions at once: it cools in summer at heat-pump efficiency and supplements winter heating without resistive-electric running costs. For a flat, a listed cottage or any home where the outside wall was never yours to use, that is a meaningful slice of energy independence, bought for the price of three holes in a wall.