One of the most surefire ways to know you need a new thermostat is when your utility bills have been gradually increasing although your household habits have stayed the same. If you live in an area with extreme summers or winters, then this reason might not be as significant since higher temperatures do affect how much your cooling or heating system has to work. But if you live in a temperate climate and you’ve noticed your energy usage spiking for no apparent reason, it very well could be time for a new thermostat.