Controls · Zoning
The highest-return control upgrade in most British houses.
The default British house has one zone and one thermostat in the hallway. Every other room runs to whatever temperature the radiator happens to deliver. Proper zoning treats each room, or each floor, as its own zone with its own schedule; usually the single largest control saving available.
Single hallway thermostat; every room to its own accident
The default house on a January evening; the spare bedroom is at 22°C nobody asked for while the kitchen where dinner is happening sits at 19°C.
Where zoning actually saves money.
A house with one thermostat heats every room to the same conceptual target, even though only two or three of them need to be at 20°C at any given hour. Zoning breaks that assumption; the bedroom drops when nobody is in it, the kitchen holds while dinner is on, and the boiler runs for fewer total minutes at a lower flow temperature.
The saving in a previously unzoned three-bed semi typically lands at 15 to 25 per cent of the heating bill. It is one of the few upgrades in the house where behaviour and hardware combine cleanly; every household has rooms that live on different schedules, and zoning is the way to price that reality into the system.
Per-room smart TRVs on schedules that match room use
Same house, per-room smart TRVs on schedules that match how the rooms are actually used; boiler down, comfort up.
Per-room TRVs vs wet zoning.
Two routes with very different disruption profiles; the timing decides which.
Smart per-room TRVs
- Strength
- £60 to £90 per radiator fitted; no plumbing changes; configurable in an evening. Whole-house install at £600 to £1,200 for a typical three-bed.
- Trade-off
- TRVs regulate the radiator, not the boiler flow; savings depend on the thermostat above them.
- Best for
- Almost every UK household adding zoning to an existing system.
Wet zoning with manifold actuators
- Strength
- Cleanest implementation; genuine hydraulic isolation of each zone; pairs beautifully with underfloor heating and heat pumps.
- Trade-off
- Plumbing changes; hard to justify as a standalone job; usually only sensible during a heating-system upgrade.
- Best for
- Renovations, extensions or heat-pump installs where the plumbing is already open.
Two-zone S-plan retrofit
- Strength
- Splits upstairs and downstairs with two motorised valves and two programmers; a cheap middle ground on existing systems.
- Trade-off
- Room-level control still absent; zones are broad-brush.
- Best for
- Households wanting a simple upstairs/downstairs schedule without smart-TRV per-radiator work.
Verdict
Zoning, honestly assessed.
Fit smart per-room TRVs across the whole house first; consider wet zoning only when the plumbing is open for a heat-pump or underfloor install.
A whole-house TRV retrofit at £600 to £1,200 typically saves £180 to £450 a year against an unzoned single-thermostat baseline; a payback well inside three years and no plumbing changes required.
Wet zoning is the gold standard but is expensive as a standalone job; add it during a heating-system upgrade where the disruption is already paid for, not as a bolt-on to a working system.
What it gives you
- Matches heating to how rooms are actually used, not to a single hallway average.
- Payback usually under three years on a whole-house TRV retrofit.
- Sits happily under an OEM heat-pump controller without interfering with modulation.
What it costs you
- TRV batteries need swapping every 12 to 24 months; not zero maintenance.
- Wet zoning is expensive and disruptive on an existing system.
- Zoning is a smaller lever than fabric; do not chase it before the loft top-up.
Why we think thisOpenClose
Reasoning
The 15 to 25 per cent saving range comes from published Energy Saving Trust field studies of TRV zoning on unimproved UK dwellings, calibrated against BEIS SAP heating profiles. Wet-zoning uplift figures come from the CIBSE domestic heating design guide (CIBSE DG12) for manifold-based systems paired with heat pumps.
Cost bands reflect UK installer quotes in 2026; smart TRVs at £60 to £90 fitted per radiator, whole-house three-bed retrofits at £600 to £1,200, and evohome-class premium installs at £900 to £1,800 fitted.
Assumptions
- The baseline is a single hallway thermostat with dumb TRVs or none at all.
- The house has at least six radiators with room-scale variation in use patterns.
- The heating source is modulating (condensing boiler or heat pump); non-condensing boilers show smaller savings.
Sources
- Smart heating controls field trial — Energy Saving Trust
- CIBSE Domestic Heating Design Guide (DG12) — CIBSE
- MIS 3005 Heat pump installation requirements — MCS
If this were our house
If this were our house with a single hallway thermostat and dumb TRVs, we would fit smart TRVs on every radiator over one weekend and leave the wet-zoning conversation for the next heating upgrade.
- 1Fit smart TRVs across all radiators (typically eight in a three-bed semi) and configure per-room schedules that match how the rooms are actually used.
- 2Leave the OEM controller (or main smart thermostat) in charge of the boiler or heat pump; TRVs sit underneath it, not in front of it.
- 3Revisit wet zoning only when the plumbing is next open for an underfloor or heat-pump upgrade.
On a house with an unmodulated older boiler, insulation and boiler replacement come first; TRV savings shrink significantly under a non-condensing system.