Smart Thermostat Installation in Sacramento

The C-wire problem

Most smart thermostats need constant 24-volt power for the screen and Wi-Fi. That power comes from the C (common) wire. Many older Sacramento homes were wired with only four or five conductors, and the C terminal at the furnace is empty.

Without a C-wire, some thermostats "power steal" by trickling current through the heating or cooling wires. That can work, but it often causes trouble:

• The thermostat goes blank or drops off Wi-Fi
• The furnace or AC clicks on and off on its own
• Rechargeable batteries in the thermostat keep dying
• The blower runs when it should not, or a heat pump chatters

How we fix it, from simplest to most work:

1. Use a spare wire. Often there is an unused conductor folded back in the wall. We connect it to C at both ends.
2. Add an adapter. A power adapter kit at the furnace can add a C-wire over the existing cable when no spare exists.
3. Run new thermostat cable. When the old cable is too short on conductors for your system, especially heat pumps and two-stage equipment, we pull a new one.

Heat pump compatibility

Heat pumps use different wiring and settings than a furnace and AC. A wrong setting here does not just waste energy. It can leave you with cold air in winter or expensive backup heat running when it does not need to.

• Reversing valve (O/B). The thermostat has to energize the valve in the right mode. Most brands use O (cool), some use B (heat). Set it wrong and heating and cooling swap.
• Auxiliary and emergency heat. Many heat pumps have electric heat strips. The thermostat should only call them when the heat pump cannot keep up, not every time you bump the setpoint.
• Outdoor temperature lockouts. Setting balance points keeps the heat strips off on most Sacramento winter days, when the heat pump alone can handle the load.
• Dual fuel. If you have a heat pump with a gas furnace backup, the thermostat decides when to switch. We set it based on your equipment and rates.
• Communicating systems. Some variable-speed systems use a proprietary control and lose features with a standard thermostat. We check before you buy.

Thinking about switching from gas to a heat pump? See heat pump installation.

Thermostat wiring reference

Terminal	Usual wire color	What it does
R, Rh, Rc	Red	24-volt power from the system transformer
C	Blue or black (varies)	Common, completes the circuit for constant power
W or W1	White	Heat (furnace), or auxiliary heat on some heat pumps
W2 / AUX / E	Varies	Second-stage, auxiliary or emergency heat
Y or Y1	Yellow	Cooling, or heat pump compressor
Y2	Varies	Second-stage cooling or compressor
G	Green	Indoor blower fan
O/B	Orange or dark blue	Heat pump reversing valve

Colors are a convention, not a rule. Installers do not always follow them, which is why we check the connections at the furnace or air handler, not just at the wall.

Zoning and multiple systems

Two-story Sacramento homes often have an upstairs that runs several degrees hotter in summer. There are a few ways thermostats help:

• Two systems, two thermostats. Each gets its own smart thermostat and schedule.
• One system with a zone panel. Motorized dampers in the ducts send air where it is needed. Each zone thermostat connects to the zone panel, not directly to the furnace, so the wiring has to be done at the panel.
• Remote room sensors. Some smart thermostats average or prioritize temperatures from sensors in other rooms, which can help a single-zone home balance day and night.
• Mini-splits. Ductless heads usually use their own controls. If you are adding a ductless mini-split to fix a hot room, ask us about control options.

If one room is always hot even with the right thermostat, the problem may be leaky or undersized ducts. See air duct sealing.

SMUD time-of-day rates and pre-cooling

Most SMUD residential customers are on the Time-of-Day (5-8 p.m.) rate. At the time of writing (2026):

• Peak hours are weekdays from 5 to 8 p.m. Weekends and holidays are off-peak all day.
• In summer (June 1 through September 30), the peak price is more than double the off-peak price, and noon to 5 p.m. and 8 p.m. to midnight are billed at a mid-peak price.
• The rest of the year has only peak and off-peak, with a smaller gap between them.

SMUD itself recommends pre-cooling the home before 5 p.m. on hot days. A smart thermostat does this automatically. A typical summer schedule cools the house a few degrees below your comfort setting in the mid-afternoon, then lets the temperature drift up slowly from 5 to 8 p.m. The house holds the coolness, the AC runs less during peak, and you are still comfortable when the Delta breeze arrives in the evening.

SMUD also runs a smart thermostat program, launched as My Energy Optimizer Partner and now part of My Energy Optimizer, which adjusts enrolled thermostats during a few summer peak events. It has grown to tens of thousands of participants. Check smud.org for current enrollment terms, compatible thermostats and any incentive.

Homes served by PG&E in Placer, El Dorado and Yolo counties, or by Roseville Electric, have different rate plans and programs. We set the schedule around whichever plan you are on.

What we check before installing

How installation works

1. Compatibility check. Tell us your equipment and the thermostat you want, or let us recommend one that fits.
2. Wiring. We confirm every connection at the wall and the equipment, and add a C-wire if needed.
3. Configuration. We set system type, stages, O/B, auxiliary heat lockouts and fan settings.
4. Testing. We run heating, cooling and fan from the thermostat and confirm the equipment responds correctly.
5. Schedule and app setup. We help you connect it to Wi-Fi and the app and set a schedule that fits your rate plan.

What does smart thermostat installation cost?

What moves the price:

• The thermostat. Whether you supply it or we do, and which model.
• C-wire work. A spare wire is quick. An adapter or new cable run takes more time.
• System type. Heat pumps, dual fuel, multi-stage and zoned systems take more setup.
• Number of thermostats. Homes with two systems or a zone panel need more than one.

Installing it during a tune-up or service visit saves a separate trip.

Where we install thermostats

We install smart thermostats across the Sacramento region, including Elk Grove, Rancho Cordova, Folsom and Natomas.

Smart thermostat FAQ