ANSWER -- It's a good idea to replace old heating systems with newer, more efficient models. These new models can work just as well or better than old systems, but they do work differently. Where old furnaces could be turned on and heat the house within a matter of minutes, new heating systems can take longer. If you want your home to be warm at a certain time, set the heat to go on about 45 minutes prior to that.
Another important factor is whether your home is 'weather-tight.' Make sure all doors and windows are properly sealed. If not, you may be losing heat at the same rate your heating system is producing it. Check with a heating contractor who can tell you whether the new unit is sized correctly for your home.
-- Associated Press