Many things in life come with a maintenance agreement or service plan as an option.
I even purchased an electric can opener and the clerk asked me if I wanted a one year warranty on it.
I had to laugh as the opener was only a few dollars anyway. I was not going to pay an additional amount to cover it in the event it broke. Now when it comes to larger purchases these make more sense. If you have a new HVAC system was installed you will probably be dizzy about all the expenses and paperwork you will receive. One of the options you have may be a service agreement. Your new system will come with the standard manufactures warranty but most of these only cover parts and not the labor that is involved in completing the repairs. A service plan involves annual maintenance and most cover some or not all of the labor costs. There is an additional charge for these types of agreements so you need to consider carefully if you need them or not. My husband is very handy and can handle changing the filters and checking the lines and such himself. So when we had our system installed we opted not to have this agreement. On the other hand, my mother in law, who lives by herself has a service agreement on just about anything she owns. She does not want to bother family members with doing minor repairs and maintenance. It works great for her. So consider your lifestyle and abilities and whether this is the right choice for you.