I Want a Smart Thermostat but Don't Have a C Wire - What Do I Do?

June 09, 2021

When you’re seeking ways to lower heating and cooling bills, installing a smart thermostat is a smart move. These devices learn your temperature preferences and routine and then develop an energy-efficient schedule to match. What’s even better is that you can adjust and monitor your settings from almost anywhere with your phone, whether you’re lying in bed or away from home. (You might even be eligible for a free smart thermostat depending on rebate programs from your utility supplier in Buellton.)

In many instances, hooking up a smart home thermostat with the support of Allstar Heating & Air Conditioning is an uncomplicated process if you have a newer house. But what if your house is older or doesn’t have the correct wiring? Can you still add a smart thermostat without C wire? We’ll help you navigate the process so you can pick the right thermostat and receive energy savings for a long time.

What Is a C Wire and What Does It Do on a Thermostat?

Many programmable thermostats run on batteries. When you’re making the move to a smart thermostat, you’ll find that many need a C wire, or common wire, for power. Without this wire, your new thermostat may cause your heating and cooling system to have glitches.

You can determine if you have a C wire by doing the following:

  1. Switch off power to the thermostat at the breaker.
  2. Take off the thermostat and check the wiring.
  3. If there are five or six multicolored wires, you have what’s required for a smart thermostat. You might be wondering what color is the C wire on a thermostat—and the answer to that is often blue.
  4. If there are three or four thin multicolored wires, you’re almost there. Check the C wire isn’t tucked inside the wall. If you can’t find one, we may be able to install one for you or you may be able to run your new thermostat without one.
  5. If you have two thick wires, you may be able to install a smart thermostat with an adaptor specifically for high-voltage systems. Or you may be able to use a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring isn’t right and you don’t want to put in new wiring.

Do Nest or ecobee Need a C Wire?

Two of the best-selling brands are the Nest smart thermostat and ecobee smart thermostat. If you have two to four wires, these thermostats may be a match for your home.

Nest says its thermostats are made to need not a lot of power and can frequently share it with your HVAC system. However, you may need to have a specialist like Allstar Heating & Air Conditioning add a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re having power problems or a battery that’s always drained.

ecobee works with 24-volt systems (ones with three to six thermostat wires) and comes with a C wire adaptor. So, you’re good if you don’t have a thermostat C wire.

Depend on Allstar Heating & Air Conditioning for Your Smart Thermostat Installation Needs

At Allstar Heating & Air Conditioning, we’re always on the lookout for ways to keep you more comfortable while keeping heating and cooling bills inexpensive. If you want to learn more about upgrading to a smart thermostat without a C wire, give us a call at 805-242-9638. We can help you choose the right model for your home and even add new wiring if required.