Like many economic questions, the one of air curtain cost-benefit depends on a number of variables. A small, unheated 36-inch (91.4-centimeter) air curtain can cost as little as $200 [source: Amazon]. On the other hand, a high velocity, heated curtain for a 9-foot by 14-foot (2.7-meter by 4.2-meter) door can run almost $450 [source: Grainger.com]. So, just like tilting and powering your air curtain to do what's needed and no more, the first trick in air curtain economics is to pay for only what you need. The size should be a no-brainer: Measure your door. Next, decide if comfort or efficiency is your end goal -- if it's comfort, go heated; if not, consider an unheated model. Finally, estimate the force your air curtain will need to counteract the force of outside air. For example, if you're fighting a windy Minnesota winter, you'll need more air at a higher speed than you'd need in an area with a milder climate and no wind.
The other benefit of air curtains is that they can help a structure earn Energy and Atmosphere points, Indoor Air Quality points, Innovation in Design points, and Indoor Environmental Quality points, all of which add up to the Leadership in Energy and Environmental Design (LEED) certification [source: Air Conditioning, Heating and Refrigeration News].
If you want to know your energy savings beyond the initial outlays, you'll have to take into account things like wind speed and energy costs. Berner International and Mars Air Systems, suppliers of air curtains, include calculators on their sites that can help estimate the costs and savings of air curtains over time. For example, an air door that costs $3,000, installed on an 8-foot by 6-foot (2.4-meter by 1.8-meter) doorway with an average outside temperature of 50 degrees Fahrenheit (10 degrees Celsius) and wind speed of 8 miles per hour (12.8 kilometers per hour) will pay for itself in almost exactly a year.