Both are Energy Star approved, and come with a pre-programmed heating/cooling schedule that will reduce your carbon footprint and save you money on energy bills (the TX500E up to $500, the TX1500E up to $180), should you choose to use it. Both have a graphic filter monitor that measures energy usage, allows you to set energy usage limits for periods of up to 365 days, and lets you know when it is time to change the furnace filter. Both have a keyboard lockout system that prevents unwanted tamperers from changing your temperature. The main differences between the two thermostats are the fact that the TX1500E has 5+1+1 day programming whereas the TX500E has 5+2 day programming, the fact that the TX500E does not have soft touch buttons like the TX1500E, and that the TX500E's display screen is not blue EL (Electro Luminescent) like the TX1500E. Both the TX500E and the TX1500E are made for use with 24 VAC systems.
