You’ll spend between $28,000 and $62,000 on air conditioning equipment, service, and energy over the next 30 years. Here’s the math.

Your specific outlay will depend a good bit on your home size, a little bit on your equipment SEER rating, but primarily on your choice of contractor. In other words, you control your cooling and heating costs principally by your contractor decision.

Here’s Why

The amount you spend on HVAC is a function of seven variables, five of which are controlled by your contractor (denoted in red below):

Equipment Costs = Average Installation Price x Replacement Frequency

Repair Costs = Average Repair Price x Repair Frequency

Energy Costs = Energy Rate x Heat Load/Actual Efficiency

You already know that your contractor’s prices are an important contributor to your total HVAC expense. But you may not realize how Replacement Frequency, Repair Frequency, and Actual Efficiency multiply your costs. These cost drivers escape many homeowners’ attention because of three false assumptions:

Assumptions 1 & 2: System reliability and longevity depend primarily on manufacturing quality. System efficiency depends primarily on SEER rating.

Reality: Your system life, reliability, and efficiency depend primarily on the practices employed by contractors when they design, install, and service your system.

Assumption 3: The costs influenced by these factors are trivial—a thousand dollars at most.

Reality: Tens of thousands of dollars are at stake. Properly installed and serviced systems can run super-efficiently for 30 years with few repairs required over the life of the system. Systems installed using mediocre practices can last a quarter as long, cost twice as much to maintain, and operate at less than 60% of their rated efficiency.

To minimize your HVAC costs you should choose your contractor as carefully as you would any other professional that’s responsible for large sums of your money.