The smart time to examine and evaluate your furnace is before the unit fails not when you begin to have problems. Age aside, some tell-tale signs that it may be time for furnace replacement are frequent repairs, soaring energy bills, some rooms or offices in your home or business are colder than others, and humidity problem. Also find out the age of your unit. Today’s models operate reliably for 20 – 30 years. If your unit is more than 15 years old, it is not a bad idea to consider replacement.