If your thermostat has a digital reading you will have to replace the batteries about every year. If your batteries go dead then guess what–your air conditioning won’t work! You’ll feel like Frosty the Snowman in August: distressed, upset, sweating profusely. One thing to be mindful of is the type of batteries to use. You will want to use lithium batteries to keep away from possible corrosion issues. Your best bet is to go with a high quality battery so you don’t have to replace them as frequently. Of course you could always continue to clean up melted candles from your mantle all summer long, but if you want the not-so-hot-and-messy route, remember to replace your thermostat batteries about once a year.