"AC tune-up" is one of the most loosely used phrases in home services. For some companies it means a technician glances at the filter, hoses off the outdoor unit and hands you a quote for a new system...

Ask the internet how often to change an air filter and you will get "every 90 days." That number was written for a house with a lawn, a few rainy months and a heating season. In Tucson, where the air ...