Buying a good Energy Star rated programmable thermostat will save you up to $180 on your annual heating and cooling bills, especially if you follow Energy Star recommendations for temperature settings. Two of the most popular programmable thermostats on the market are the Honeywell RTH7500D and the Lux Products TX1500E. This post will look at the relative merits of these two programmable thermostats.

Both the Honeywell RTH7500D and the Lux Products TX1500E are compatible with a wide range of 24-volt heating and cooling systems including single stage and multi stage systems, gas pumps and electric fireplaces. Both thermostats allow you to program in your heating and cooling requirements for every day of the week. And for each day of the week the Honeywell RTH7500D and the Lux Products TX1500E allow you to set four different time zones. Thus, you can have the heating on low while you are sleeping, have it come on just before you get up, have it go off while you're at work and have it come on again just prior to your return from work. Both the Honeywell and Lux Products Thermostats also have vacation settings to allow you to keep the HVAC systems just ticking over while you are away for several days at a time. And both programmable thermostats tell you when your filters need changing.

There are, however, several differences between the two thermostats. The first is the price. The Honeywell RTH7500D Programmable Thermostat costs about $75 whereas the Lux TX1500E Smart Temp Programmable Thermostat costs around $40.

In favour of the Honeywell RTH7500D it has a better designed interface. In contrast several reviewers have complained about the stiff buttons on the Lux Products TX1500E. And furthermore, the Honeywell can automatically switch between heating and cooling systems to make sure the room temperature is exactly how you want it. The Lux Smart Temp Programmable Thermostat doesn't have this feature.

In defence of the Lux Products TX1500E Smart Temp Programmable Thermostat is has a number of features not found on the Honeywell RTH7500D. It tells you the relative humidity in a room which is useful if you have hardwood or bamboo flooring. It also has a number lock on it to stop children playing with the settings. But the most important difference between the Honeywell RTH7500D and the Lux Products TX1500E is that the Lux model has swing control. This means you change the temperature differential or, in other words, the point at which the boiler or cooler kicks in. On the Honeywell RTH7500D the swing is fixed at +/- 0.25 degrees. This means that if you set the thermostat at 78 degrees that if the room temperature drops to 77.75 degrees or rises to 78.25 degrees then the heating/cooling comes on. In really hot or cold weather this can cause the HVAC system to continually be turning off and on. This constant on and off can do damage to your HVAC system.

In contrast, the Lux Products TX1500E Smart Temp Programmable Thermostat has swing control. This allows the user to set the temperature differential between +/- 0.25 degree and +/- 1 degree. This is a key difference between the Honeywell RTH7500D and the Lux TX1500E and perhaps a vital one for those people who live in extremely hot or cold climates.

So to sum up, both the Honeywell RTH7500D and the Lux Products TX1500E are excellent programmable thermostats that will save you money. Whereas, the Honeywell can more accurately regulate the room temperature, the lack of swing control means that the Lux Products TX1500E is the better programmable thermostat for extreme weather conditions because you can stop the HVAC coming on 10 times an hour.