Came from Nest before Google but wanted a HomeKit compatible smart thermostat. Homebridge support was patchy and only worked if you didn't convert your account to a Google Home account, which they all force you to do eventually. So I took two EcoBees. The Nest worked fine with my 2-wire system, but the EcoBee requires a C-wire or 24V AC power source. After reviewing all the options and trying to pull new fishing line to the thermostat, I decided that using the C-Maker would cause the fewest problems. I used the purchase to redo the wiring on the side of the boiler to clean it and label everything. There is quite a bit of wiring to disassemble on the side of the boiler, especially if you have multiple zones, but if you download additional wiring diagrams from their website you can compare your existing wiring to that required for a C maker. It would be nice to have a terminal block on the boiler side of the module to allow for a cleaner installation. Overall the setup went well and I don't see any issues with the thermostats. If you are installing a smart thermostat yourself and want an inexpensive solution, you might want to consider a 24VAC plug-in transformer, but this may not be suitable. Good, because the wall plug and the cable are connected to the thermostat. Installing a smart thermostat yourself is an expensive but simpler alternative to the C-wire that keeps the room strictly. If you want a professional to install a smart thermostat, you're better off using a cable instead of this solution.