When and how should I replace the batteries in my Honeywell thermostat?

Replace batteries immediately when the low battery icon appears, which occurs about two months before depletion. You should also replace batteries once a year or before leaving home for more than a month. To replace, gently press to loosen the thermostat, pull it from the wall mount, and insert two fresh AA alkaline batteries in the back. If batteries are inserted within two minutes, time and day settings are preserved.