Bests & Worsts Reviews from Amazon

UPDATE (Aug 2020): the RTH8500D served well for 10 years. However, the world has changed and WiFi thermostats are really worth considering. Honeywell's T5 Lyric is an impressive unit that has a decent enough app that does the basics of letting you control your thermostat from anywhere and has the same scheduling functionality of the 8500D model. A feature on the T5 (unavailable on the 8500D) that is great for vacation homes is the Auto Changeover feature where we set a low and high setpoint when we're away (40F/87F) and the thermostat does everything for you re heat/cool mode selection. The T5 also has a Vacation Schedule feature that works very nicely from the app and is significantly easier to use than the 8500D Vacation Hold feature. The T5 can make you down right lazy by letting you adjust the thermostat from your couch. The Nest and Ecobee units are nice too, but at half the price you'd be happy with the T5. If you're still set on the 8500D, I have three on the shelf🙂 UPDATE (May 2011): We recently installed another RTH8500D in our bedroom. The "click" of the relay contact when the thermostat calls for activation annoys my wife who has rather sensitive hearing. I contacted Honeywell and they said the clicking sound is unavoidable at the current time and suggested insulating the back plate of the RTH8500D with 1/8" Styrofoam to deaden the relay sound. I temporarily tried a thick folded piece of clothing material and didn't notice any difference. After reading other Honeywell thermostat reviews, the clicking sound seems to be universal across many of their thermostats. So, if considering a bedroom application, you may want test the unit to ensure it's within an acceptable noise level . ORIGINAL REVIEW (2010): I have both the Honeywell RTH7600D (bought at Costco for around $65 and packaged there as model RCT8101A) and this Honeywell RTH8500D. Both units are very good with the one major difference being the "Vacation Hold" feature; the 8500 has it and the 7600/Costco version does not. The programming interface is different as well, however, one is not necessarily better than the other. The 7600 unit is a little easier to program whereas the 8500 offers a shortcut that allows multiple days to be programmed at once. Since you'll likely program the unit infrequently, I don't think this should necessarily be a consideration unless you are an installer of these units where time is money; then the 8500 is the unit of choice. The Costco version for me is going back because it lacks the Vacation Hold feature. If you travel or not at home frequently, the Vacation Hold feature allows you to hold the temperature, say, at 50 degrees for 10 days while you take off for a ski trip. With this feature, once the timed Vacation Hold is over, the thermostat resumes it's normal programming schedule. So, when you arrive home, the house temperature is at a comfortable level. The Costco version allows you to manually override the program schedule, however, you must manually remove the override as well. Therefore, when you arrive home from your ski trip, you come home to a cold house and you'll need to manually reset the thermostat and wait for the house to warm up. If this is not an important feature for you or you're are at home most of the time, go for the Costco version and save about $40. Otherwise, the RTH8500D is an excellent unit that has worked quite well for me over the past several years.