Comparison Guide
Water-cooled vs split AC: which is right for a London flat?
A side-by-side comparison of traditional split-system air conditioning and water-cooled "invisible" AC — covering planning permission, installation cost, noise, efficiency and the reality of getting leaseholder approval in a London apartment.
The short answer
If your flat has a private garden, roof or discreet balcony where an outdoor unit is allowed, a traditional split system is usually the cheapest and most straightforward option. If you live in a mansion block, listed building, conservation area or any flat where the freeholder refuses external units, water-cooled AC is often the only route to a working, approved system.
The rest of this guide breaks down the differences in detail so you can decide before booking a survey — or take the comparison to your freeholder or managing agent.
Side-by-side comparison
Split system AC
An outdoor condenser connected to one or more indoor units by refrigerant pipework. The industry standard for houses and flats with permitted external space.
Water-cooled AC (Parkair MCW)
A single water/air heat pump installed inside the flat — no outdoor unit at all. Serves up to 5 rooms and delivers heating, cooling and dehumidification.
When a split system makes sense
Trade-offs
When water-cooled is the smarter choice
The Parkair MCW 2.0
Our recommended water-cooled system for London flats. R32 inverter heat pump, A+++ efficiency, up to 5 rooms from a single indoor module. No outdoor unit, no planning hassle, and typically approved by freeholders on first submission.
See the systemWhat you'll actually pay in London
Split system
- • Single room install from £1,495
- • 2–3 rooms typically £3,500–£6,000
- • Planning consultant (if needed): £500–£1,500
- • Scaffold / cherry picker: £400–£1,200
Water-cooled
- • 1–2 rooms typically £4,000–£6,500
- • 3–5 rooms typically £7,500–£12,000
- • No planning cost — no external works
- • Faster License to Alter approval
Frequently asked questions
What's the main difference between water-cooled and split AC?+
A split system uses an outdoor condenser mounted on the wall, balcony or roof, connected to indoor units by refrigerant pipes. A water-cooled system (like the Parkair MCW) has no outdoor unit — a single water/air heat pump lives inside the flat and connects to compact indoor units via water pipes.
Which is cheaper to install?+
Traditional split AC is typically cheaper for a single room (from ~£1,495 installed). Water-cooled systems cost more up front (~£4,000–£12,000 for a multi-room flat) but often avoid the higher costs of scaffolding, façade licensing, planning consultants and long freeholder negotiations in London.
Which is more energy-efficient?+
Both can reach A+++ efficiency. Modern R32 splits have slightly better raw SEER/SCOP figures, but water-cooled systems recycle waste heat between rooms and lose less through long external pipework — so real-world running costs are very similar in a typical London flat.
Which is quieter?+
Water-cooled wins for neighbours: there is no outdoor compressor, so nothing sits on the façade or balcony. Indoors both are whisper-quiet (19–26 dB). Splits can cause noise complaints if the outdoor unit is close to a neighbour's window.
Do I need planning permission?+
Split AC often needs planning consent in London — especially in conservation areas, listed buildings and any flat where the outdoor unit is visible from the street. Water-cooled AC has no external unit, so planning permission is not required and the License to Alter is usually approved without issue.
Which is better for a leasehold flat?+
For most London leaseholders, water-cooled is the pragmatic choice. It removes the most common reasons freeholders refuse consent (façade impact, noise, planning), which is why we install it as standard in mansion blocks, listed buildings and conservation areas.
Not sure which system fits your flat?
Book a free survey — we'll tell you honestly which option will get past your freeholder and match your budget.