We service ALL brands makes and models!
Free Install Estimate

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

June 09, 2021

When you’re seeking approaches to lower heating and cooling expenses, upgrading to a smart thermostat is a smart idea. These devices adjust to your favorite temperatures and routine and then create an energy-efficient schedule to match. What’s even better is that you can change and keep an eye on your settings from just about anywhere with your phone, whether you’re relaxing in bed or away from home. (You might even be able to receive a free smart thermostat depending on rebate programs from your utility supplier in the Bay Area.)

In most instances, hooking up a smart home thermostat with the assistance of Contra Costa Heating & AC is a simple job if you have a new home. But what if your home is older or doesn’t have the proper wiring? Can you still add a smart thermostat without C wire? We’ll help you navigate the process so you can choose the right thermostat and receive energy savings for years to come.

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

The majority of programmable thermostats use batteries. When you’re upgrading to a smart thermostat, you’ll find that many have to have a C wire, or common wire, for power. If you don’t have this wire, your new thermostat could cause your heating and cooling system to malfunction.

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

  1. Cut power to the thermostat at the breaker.
  2. Remove the thermostat and find the wiring.
  3. If there are five or six multicolored wires, you have what you need for a smart thermostat. You might be pondering what color is the C wire on a thermostat—and the answer to that is usually blue.
  4. If there are three or four thin multicolored wires, you’re nearly there. Make sure the C wire isn’t hidden in the wall. If you can’t find one, we may be able to add one for you or you may be able to use your new thermostat without one.
  5. If you have two thick wires, you may be able to use a smart thermostat with an adaptor designed 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 most popular brands are the Nest smart thermostat and ecobee smart thermostat. If you have two to four wires, these thermostats may work for your home.

Nest says its thermostats are designed to run on minimal power and can typically share it with your heating and cooling system. However, you may need to have a specialist like Contra Costa Heating & AC add a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re having power problems or a battery that’s constantly drained.

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

Depend on Contra Costa Heating & AC for Your Smart Thermostat Installation Needs

At Contra Costa Heating & AC, we’re always on the lookout for methods to keep you cozier while keeping energy bills reasonable. If you want to learn more about installing a smart thermostat without a C wire, contact us at 510-343-9841. We can help you pick the right model for your residence and even install new wiring if necessary.