I’ve been doing a bit of research to try and find the cheapest way of creating a zoned heating system. The baseline is the commercial products from the likes of Honeywell and HeatGenius. The Honeywell evohome with the special offer on a pack of four wireless TRVs will set you back £415, maybe less if you shop around. The HeatGenius will be an eye-watering £489 and that’s without fitting costs.
So how to do it cheaper? Looking at Open Source solutions it seems there are a few options. OpenHAB is a good software solution that can be run on a spare PC, laptop (low power netbook with a SSD would be suitable) or a NAS box, no need to buy new hardware. This needs a suitable wireless dongle for communication with the TRVs and the Aeotech Z-Stick USB at £41 looks like a good solution.
The cheapest wireless TRVs I’ve found are the StellaZ, which work on the Z-wave protocol and can be found for around £48 each. This is often a significant factor in the cost of multi-zone systems, the incremental cost of adding another zone is that of the TRVs, one for each radiator in the zone. So for four zones, assuming one TRV per zone, would come to just £280, significantly cheaper than the evohome and HeatGenius. Of course, setting this up will be harder than the commercial offering and probably only suitable for the hobbyist, but at least on paper it is possible to do it cheaply.