Adding smart thermostats

[HenryGregory]

I am thinking of getting a set of smart thermostats to help keep my heating costs down.
I have a combi boiler, no hot water tank and two thermostats. One for downstairs and one for upstairs radiators.

They are battery powered thermostats and this is the cabling behind in the backbox:

Can anyone tell me if the above cabling would be enough to run something like a Nest Learning Thermostat or Nest Thermostat E?
I am not sure I am the best to wire it all in as never done it before, so would likely get an electrician but wanted to check I have the correct cabling in the walls before spending out on the thermostats.

At the moment, the brown and black leads are wired into the back of the thermostat like this, such that the thermostat is literally operating as a switch using it's in built batteries:

Thanks in advance

 

[flameport]

A Nest E can be used there as it's battery powered. It connects to the same two wires used for the existing thermostat.

Others might be possible but most require 230V AC so it depends on what those wires are connected to.

 

[ericmark]

Nest e as said will work, but not sure it will do what you want, in the main UK central heating is controlled by the TRV (thermostatic radiator valve) there are broadly speaking three types.

Mechanical
Electronic self contained
Electronic linked to hub or wall thermostat

The wall thermostat can control temperature, and this works well with a open plan house, or hot air central heating, but in the main they are there to stop the boiler cycling when all TRV's are satisfied.

The word "Smart" can mean the thermostat works out how long it takes to heat up a room, so it does not over shoot, so stops the hysteresis. But it can also simply mean it connects to internet.

Both wall thermostats and TRV's can be set for geofencing, but how varies, I used Nest Gen 3 which was rather disappointing, all the control you have is setting eco and comfort, you can't set distance, the same with the Energenie MiHome TRV's, you just set two temperatures, however other makes I am told you can set the distance from home when the heating switches on.

Some thermostats simply switch on/off, others slowly alter boiler output or TRV flow. EPH it seems makes one which can be set to run as master or slave and control the boiler using OpenTherm but zone valve on/off, but not all boiler can work with OpenTherm, some boiler can only use their own make of modulating wall thermostat (modulating means turning boiler up/down rather than on/off), and some boiler only way to control modulation is using the circulating water, and some don't modulate.

I use cheap electronic TRV's like this no internet, just bluetooth, but I have an oil boiler, they only cost me £15 each in 2019, the Drayton Wiser TRV seems to have the best spec as far as I can tell, but people only tend to fit electronic TRV's once, so hard to compare.