One brand rarely covers a whole house well. This note is how we ran our own home after trying Nest, then Honeywell Evohome (now sold under Resideo), then both at once. It is a dated install record, not a 2026 shopping list. Google is no longer launching new Nest thermostats in Europe; Evohome is still a serious zoning system. The wiring idea still holds.
What we tried first
Like a lot of UK houses, the first “smart” heating kit that stuck was a Nest Learning Thermostat — 2nd generation, then later the 3rd. Before that, remote access meant port-forwarding a router. Nest removed that friction. We then fitted Evohome because we were installing it for clients and needed a house to learn on: hot-water kit, HR92 radiator heads, and a BDR91 on a single wet underfloor zone. Nest Protect and a Nest camera stayed. The 3rd gen Nest came out of the heating loop for a while.
The household problem
Two people in the house needed to change the temperature without a manual. One is a heating engineer used to traditional controls and a little UFH. One had only just started using a smartphone. Both were fine with the Nest ring. Neither wanted to drive Evohome day to day, even though Evohome is the better zoning tool.
So we put the Nest Learning Thermostat 3rd generation back as the only device allowed to call the boiler, over OpenTherm. Evohome stayed on the radiators and the UFH zone but cannot start the boiler. It only opens or limits emitters inside the heat Nest has already asked for. If Nest is satisfied, the boiler stays off even if a bedroom head is wound up.
Heat source
- Intergas Combi Compact RF36
- Priority domestic hot water (PDHW)
- Solar thermal into the same hot-water arrangement
OpenTherm from Nest lets the Intergas modulate instead of a plain on/off switched live. PDHW keeps tap priority without a cylinder the way a system boiler would. Solar thermal is why this house is not a textbook “combi only” story — the diverter and store side are house-specific. Do not copy the badge list onto a different property.
Doorbell and voice, same hybrid idea
We added a Nest Hello (now the Google Nest wired doorbell) and a Honeywell wired chime, USB-powered, switched through a relay from the Nest Hello chime kit. Nest for the face the household understands; Honeywell for a chime that actually sounds like a doorbell. Google Home Mini speakers and one Amazon Alexa sat on the same Wi-Fi. A TP-Link plug watched the boiler’s electrical use. None of that is required for the heating logic.
What we said we would do next — and what died
In 2019 the next step was a single dashboard: Conrad Connect, or a Raspberry Pi on OpenHAB, plus IFTTT-style rules. Conrad Connect shut down. We did not ship a published OpenHAB config for this house, so this page does not pretend that layer exists. The useful rule from that paragraph still stands: prefer kit that still heats if the internet is down. Nest and Evohome both keep local schedules when the WAN drops; a cloud-only gadget does not.
If you are buying in 2026, the Nest Thermostat E is the leftover budget Nest in Europe. It cannot run stored hot water. The 3rd gen Learning Thermostat in this study can. Google is not launching a new UK Nest. Evohome remains the industrial zoning half of the same idea.
What we would still do
- One household-facing thermostat that everyone will actually turn.
- A second system only where you need room limits or UFH, and only if it cannot fight the boiler.
- OpenTherm (or the maker’s modulating bus) on the boiler call.
- Voice and cameras as extras, not as the thing that starts the burner.
Related
- Case studies
- Nest Thermostat E
- Smart thermostats
- OpenTherm boilers and controls
- Priority domestic hot water
- Solar thermal
- Nest underfloor heating
- Intergas
A 2019 first-person install note, lightly updated in October 2026. Not a DIY wiring guide. Gas work in the UK needs a Gas Safe registered engineer. Product names (Nest Hello, Honeywell Evohome, Conrad Connect) are left as they were, with the current name in the text where the old one would mislead.