A: I say both are correct. Here is why. At the minimum you should have your unit correctly serviced once a year. I recommend twice a year to save money. Heat pumps need to be serviced spring and fall because of the way they work in heat and cool. The coils need to be clean to maintain airflow and heat transfer efficiency. Refrigerant levels need to be checked to maintain performance. A small leak and an improper defrost cycle can cost you as much as $200 a month on your electric bill. With gas heat the burners need to be cleaned and heat exchangers checked for cracks so carbon monoxide does not enter the home. It's amazing how many dirt dobbers' nests we find in combustion motors that cause them to fail and something as simple as a spider's web causing improper combustion in burners. Be Comfortable!