Your experience is highly atypical in most of the US. The common setup is a single-stage heat/cool installation with 4 color-coded wires. It's all low-voltage

Your experience is highly atypical in most of the US. The common setup is a single-stage heat/cool installation with 4 color-coded wires. It's all low-voltage (24VAC) and the biggest problem most people run into is an older 2-wire setup (single-stage heat only), where the programmable thermostat can't be vampire powered from the circuit and either cuts out when it clicks the relay on to fire the furnace, or simply needs to be a battery-powered unit. With all the eco-stuff and increased heating costs, installation of programmable thermostats by low-skilled homeowners is actually pretty common.