I have just received the Nest thermostat for Christmas and the existing thermostat is part of the utility PeakSave program in Acton, Ontario.

When I looked at the thermostat wiring there is only 4 wires, one of which is connected to the K terminal. Tho others are connected to the R, W & C

Tracing the wire from the K terminal on the existing Honeywell thermostat, it goes to a HoneywellTHP9045A1007 add-on that apparently splits the G & Y signal. Is this the same situation with everyone else who has posted here?

Thanks for your replies

Here's something I found. Maybe it will help. Honeywell THP9045A1023 Prestigeâ„¢ WireSaver Module (http://www.alpinehomeair.com/viewproduct.cfm?productID=453060252)

BTW, Good luck with your Nest. I don't hear a lot of good reports about them. I believe simpler is better.