Summary

Smart thermostats moved from a premium upgrade to a baseline expectation in a single decade. The 2018 Boiler Plus regulations require any new gas boiler installation to include a "smart" control — load compensation, weather compensation, or a smart thermostat with optimisation features. The market has standardised around Hive, Nest, Tado, Drayton Wiser, Honeywell Evohome, and manufacturer-specific systems (Worcester Wave, Vaillant vSMART, Ideal Halo).

For tradespeople the pricing decision is: is this a like-for-like swap (existing wired thermostat, new smart thermostat in its place, customer connects to Wi-Fi), or is this a full system install (multi-zone, smart TRVs, hub at the boiler)? The price spread is 3–5×, and customers usually start the conversation thinking they want a simple swap and end the conversation wanting full multi-zone control after the trade explains what's possible.

Two technical drivers determine the cost: the boiler's connection options (basic on/off, OpenTherm 4.0, eBUS, or manufacturer-specific protocols), and the routing for the new control wiring (existing 3-core+earth cable often suffices for a like-for-like; new installs may need cable runs to a boiler hub). The trade reality: many older boilers don't support OpenTherm, in which case the smart thermostat works only in on/off mode and the customer loses the modulation benefits that justified buying it.

Key Facts

Quick Reference Table

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Job Type Material Cost (Trade) Labour Hours Customer Price (S&F)
Like-for-like swap (Nest/Hive E) £80–£180 1.5–2.5 £120–£280
New install — hub at boiler + thermostat £150–£280 3–5 £250–£500
New install with OpenTherm conversion £180–£350 4–6 £350–£650
Multi-zone (2 zones, hub + 2 thermostats) £250–£450 5–8 £500–£900
Full smart TRV install (10 radiators) £350–£600 6–10 £600–£1,200
Tado / Hive whole-house with smart TRVs £600–£1,200 8–14 £900–£1,800
Honeywell Evohome 8-zone £800–£1,500 10–16 £1,200–£2,200
Smart Thermostat Typical Cost (Trade) OpenTherm?
Nest Learning Thermostat 3rd gen £180–£220 Yes (with adaptor)
Hive Active Heating + Receiver £150–£200 No (on/off)
Tado Smart Thermostat £170–£220 Yes
Drayton Wiser Hub Kit £110–£160 Yes (with module)
Honeywell Evohome system £350–£500 (basic) Yes
Worcester Wave (boiler-specific) £170–£250 Native EMS
Vaillant vSMART (boiler-specific) £180–£280 Native eBUS
Ideal Halo £130–£180 OpenTherm
Component Trade Cost
Wireless room thermostat (replacement) £80–£180
Wired room thermostat (replacement) £60–£120
Boiler hub/receiver £40–£100
Smart TRV per radiator £40–£80
Wireless room sensor (additional) £40–£70
Bridge/gateway (for some systems) £40–£90
3-core + earth cable per metre £1–£2
Junction box (BS 5733) £4–£10

Detailed Guidance

Pricing Logic

Build the price from:

  1. Hardware — Pass through trade cost of thermostat + hub at customer-facing tier; mark up appropriately
  2. Like-for-like vs new install fee — Like-for-like is fundamentally a swap; new install includes hub fitting and cable to boiler
  3. Per-zone or per-TRV add-on — Each additional zone or smart TRV adds material + 30 min install
  4. Setup and tuition — 30–60 min to set up the customer's account, register devices, and demonstrate use
  5. Visit setup fee — vehicle, tools, certificate

A typical "Hive replacement" for a customer who has Wi-Fi: £200–£350 customer price. A typical "Tado with 6 smart TRVs" for a 4-bed semi: £700–£1,200 customer price.

Like-for-Like Swap

The simplest job:

  1. Customer has an existing wired room thermostat (typically Honeywell DT90, Drayton RTS2, or similar)
  2. New smart thermostat replaces it at the same wall position
  3. Existing 3-core+earth cable reused
  4. Hub (if separate) typically located at the boiler — wired to boiler's permanent live + switched-live demand inputs
  5. Customer Wi-Fi credentials needed for setup

Time: 1.5–2.5 hours. Material: thermostat plus possibly a wireless receiver hub at the boiler.

The trap: some smart thermostats need a SEPARATE hub at the boiler, NOT just the unit at the wall position. The existing wired thermostat had a single point; the new smart system needs a wired connection at the boiler AND a wireless thermostat unit at the wall position. This may require new cable to the boiler (in addition to the existing thermostat cable) if the hub isn't already there.

New Install

When there is no existing wired thermostat (e.g. customer has a programmer at the boiler only, controlled by a manual radiator valve), the install adds:

  1. Cable from boiler to thermostat location (typically 3-core+earth, run via loft/floor void)
  2. Hub at the boiler with wired connection to boiler demand input
  3. Wireless or wired thermostat at the wall position
  4. Setup and commissioning

Time: 3–5 hours. Material: thermostat, hub, cable, fixings.

OpenTherm vs On/Off

Two ways a thermostat tells the boiler what to do:

Check the boiler's OpenTherm status:

The customer's smart thermostat selection matters here. Hive Active Heating is on/off only — no OpenTherm option. Tado, Nest (with adapter), Drayton Wiser are OpenTherm. Honeywell Evohome is OpenTherm + modulating.

If the customer specifically buys a smart thermostat to "improve efficiency", and their boiler is on/off only, the efficiency gain is much smaller than expected. Set the expectation honestly.

Multi-Zone and Smart TRVs

Smart TRVs (Tado V3+, Drayton Wiser, Honeywell Evohome) replace existing manual TRVs and provide per-radiator temperature control. Each is battery-powered (typically 2 × AA, 18 month life) and wireless to the hub.

Use cases:

Per-radiator install is 30–45 minutes: shut off radiator, replace existing TRV head with smart TRV head, register to hub, set initial temperature. Note: the radiator valve body (the part screwed into the radiator) is reused; only the actuator head is replaced. Some smart TRVs require a specific valve body type, in which case the whole valve is replaced (£30–£60 more per radiator material, 15 min more labour).

Boiler Plus Compliance

For any NEW boiler install:

  1. Boiler Plus requires one of: load compensation, weather compensation, FGHR, OR smart control with automation/optimisation
  2. A Nest Learning Thermostat with OpenTherm to a Worcester Greenstar (modulating boiler) satisfies "load compensation + smart control"
  3. A Hive Active with on/off relay to the same boiler satisfies "smart control with automation" but NOT load compensation
  4. Some installs use a manufacturer's bundled control (e.g. Worcester Wave with the boiler) — typically the most efficient pairing

Document the Boiler Plus compliance in the boiler commissioning sheet so it's clear what scheme was used.

Customer Account Setup

Modern smart thermostats require:

  1. Customer creates an account with the manufacturer (Hive, Nest, Tado etc.) using email + password
  2. Customer downloads the manufacturer's app
  3. Customer registers the new device(s) to their account
  4. Tradesperson connects device(s) to customer's Wi-Fi network (need 2.4GHz typically)
  5. Schedules and preferences set up either by tradesperson during commissioning or by customer afterwards

The customer-side account is THEIR account, not the tradesperson's. Don't set up customer Wi-Fi devices under your own account; once your phone leaves their property, the devices belong to them.

Worked Example: Tado Whole-House with 6 Smart TRVs

Job: 4-bed semi. Existing Honeywell DT90E wired thermostat in hall. Customer wants Tado smart system with smart TRVs on 6 of 10 radiators (the others stay manual). Boiler is Worcester Greenstar 30CDi (OpenTherm capable).

Item Cost
Tado Smart Thermostat Starter Kit (V3+) £180
Tado Bridge £40
6× Smart Radiator Thermostat (V3+) £288
OpenTherm adaptor (if needed) £45
3-core + earth cable (5m) £8
Junction box £6
Sealant, fixings £10
Materials subtotal £577
Labour 6 hours @ £55/hr £330
Setup, customer tuition, schedule programming £80
Boiler Plus commissioning paperwork £35
Labour subtotal £445
Subtotal £1,022
Markup 20% £204
Net price £1,226
VAT 20% (if registered) £245
Customer price (VAT-reg) £1,471

Within the £900–£1,800 band quoted for Tado whole-house with smart TRVs. Customer perception of "I just want a smart thermostat" usually starts at £200; the honest quote that includes the multi-zone TRVs and proper commissioning is £1,500. Walk them through the difference; let them decide on scope.

Frequently Asked Questions

Can I install a smart thermostat without replacing my boiler?

Yes, in almost all cases. The smart thermostat communicates with the existing boiler using the standard heating-demand signal (24V or mains-switched). For best efficiency, the boiler should support OpenTherm — most boilers after ~2010 do. Pre-2005 boilers may require a hub that emulates the older control signal.

Will a smart thermostat save me money?

Honestly: a smart thermostat with proper scheduling and learning saves 5–15% of heating cost in typical UK homes. The bigger savings come from: (1) actually using the schedule (most non-smart customers leave heating on all day), and (2) having multi-zone control to heat only occupied areas. A £180 smart thermostat saves perhaps £100–£300/year on a £1,500 annual heating bill — payback 1–3 years.

Do I need Wi-Fi for a smart thermostat?

For most current systems, yes — the hub connects to the home Wi-Fi to relay control to the manufacturer's cloud and back to the customer's app. Some hubs use Zigbee or Z-Wave between the hub and the room sensors, with Wi-Fi only at the hub. Customers in remote areas with poor broadband should verify their Wi-Fi reaches the boiler location before committing.

What's the difference between OpenTherm and on/off control?

OpenTherm allows the thermostat to tell the boiler what output power to run at (modulating, e.g. 30% of capacity), so the boiler runs at low power continuously rather than cycling on/off. On/off control just tells the boiler to fire at full capacity. OpenTherm gives ~10–15% better seasonal efficiency on a modulating combi boiler; on a non-modulating boiler, there's no benefit either way.

Can I install smart TRVs without changing the radiator valve body?

Most smart TRVs include an adapter that fits the common UK valve body threads (M30 × 1.5 and M28 × 1.5). Some older radiator valves (pre-1990 designs) need a complete valve replacement (£30–£60 per radiator material, 15 min more labour each). Check the valve type during the survey before quoting per-radiator.

Regulations & Standards