What is a common issue with outdated programmable thermostats?

Outdated programmable thermostats often lack modern energy-saving features that are prevalent in newer smart thermostats. This includes advanced programming options, learning capabilities, and adaptive scheduling, which can optimize energy use more effectively. Additionally, they may be less user-friendly, as they often come with more complex programming interfaces that do not easily allow customers to modify settings. These shortcomings can lead to inefficient heating and cooling operations, resulting in higher energy bills for homeowners.

The other options touch on issues that may exist but are not as universally applicable to all outdated programmable thermostats. Battery replacements are a concern for some models but do not capture the broader impact of outdated features. Limitations in functioning modes may apply to certain models but are not indicative of all outdated units. Size issues are not commonly associated with programmable thermostats in general, as most are designed to fit standard wall spaces.