Do I need to run new wire for a smart thermostat?

Question

Accepted Answer

Only if your existing wire doesn't have a C-wire (common wire). Check behind your current thermostat — count the wires. If you have 5+ wires, you probably have a C-wire. If only 4 wires, you either need new 5-conductor wire or a C-wire adapter kit.

Best Thermostat Wire Kits 2026