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

June 09, 2021

When you’re looking for ways to lower heating and cooling costs, getting a smart thermostat is a wise decision. These devices adjust to the temperatures you like and routine and then develop an energy-efficient schedule that fits. What’s even better is that you can change and monitor your settings from almost anywhere with your phone, whether you’re sitting in bed or away from home. (You might even be eligible for a free smart thermostat depending on rebate programs from your utility provider in Paso Robles.)

In many instances, adding a smart home thermostat with the support of Paso Robles Heating and Air is a simple job if you have a newer house. But what if your home is older or doesn’t have the right wiring? Can you still add a smart thermostat without C wire? We’ll help you navigate the process so you can choose the proper thermostat and enjoy energy savings for years to come.

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

Most programmable thermostats need batteries. When you’re upgrading 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 ascertain if you have a C wire by doing the following:

  1. Cut power to the thermostat at the breaker.
  2. Take off the thermostat and find 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 typically blue.
  4. If there are three or four thin multicolored wires, you’re almost there. Make sure the C wire isn’t rolled up in the wall. If you can’t find one, we may be able to put in 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 use a smart thermostat with an adaptor specifically for high-voltage systems. Or you may be able to operate a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring is incompatible and you don’t want to replace it.

Do Nest or ecobee Need a C Wire?

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

Nest says its thermostats are made to require very little power and can frequently share it with your heating and cooling system. However, you may need to have a professional like Paso Robles Heating and Air install a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re running into power problems or a battery that’s constantly drained.

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

Rely on Paso Robles Heating and Air for Your Smart Thermostat Installation Needs

At Paso Robles Heating and Air, we’re always seeking ways to keep you comfier while keeping heating and cooling expenses reasonable. If you want to learn more about upgrading to a smart thermostat without a C wire, reach us at 805-203-8667. We can help you choose the right model for your house and even add new wiring if needed.