For Monday's GreenSpace column, I wrote about programmable thermostats.

They were supposed to make saving energy -- and money -- so easy. You could set the thing to automatically reduce the temperature during certain hours, raise it at other times.

But ample evidence exists to show they aren't working so well because people can't figure them out. In interviews with people, they kept comparing some of these devices to old VCRs, notorious for their difficulty to program.

Wow, did that ever open up the floodgates. Many people have shared their tales of woe about programmable thermostats.

Others were horrified. "If you can't figure out how to use one, you shouldn't be driving an automobile," one caller grumped.

Here's another response:

"I am very lucky to be computer literate and involved not only in my home, but also the heating system in my office. I have been using programmable thermostats for over 10 years and love them.

"Recently I had an issue and ran into a problem I have seen too many times before. Working with a factory authorized technician, I supervised the installation of a very advanced heat pump system with a very advanced thermostat. When questions came up that I needed answered, I called the company (Carrier/Trane) consumer help line. I was told the help line does not talk to consumers. Their job was to tell the consumer to call their factory authorized technician who could call them for help. He was less successful than I was.

"While I was able to work out my problem, as long as the major heating/air conditioning equipment makers have so little consumer orientation, these thermostats don't have a chance. Quite a shame."

One question that comes up a lot: How low can you go in turning down the heat at night? Many people fear that it will take more energy to heat the house up in the morning than to just keep it warm all night. Here's Energy Star's answer:

"It is a common misconception that it takes more energy to heat up a cold house than it does to keep a house warm all the time. Turning down the thermostat will always save energy, as will turning up the air conditioner temperature setting. Heat moves from hot to cold, and the rate of heat transfer increases with greater temperature differences between inside and out. Smaller temperature differences between your house and outside generally means you’ll lose less heat (or air conditioning) from inside the house to the outside. Therefore, you will save energy by only heating or cooling as much as necessary, for the occupants and time of day."

Here's an Energy Star site with more information and tips on temperature settings.

For an Energy Star video showing how to use a programmable thermostat, click here.