A smart thermostat installed in Sacramento typically costs $250 to $500 all-in. The thermostat itself — Ecobee Premium, Google Nest Learning, Honeywell T10, Emerson Sensi — runs $130 to $300. Installation adds $100 to $250 depending on whether the existing thermostat wiring already has a common (C) wire for the thermostat to pull 24V power from.
No-C-wire installations are where the job stops being a quick swap. Most smart thermostats need continuous 24V power to run their screens, Wi-Fi radios, and cloud integration. Older Sacramento homes — especially pre-1990 single-zone systems — often have only four thermostat wires, none of which is a C-wire. Options are: run a new C-wire from the air handler, use the thermostat's power-adapter kit (Ecobee includes one), or install a cube/add-a-wire accessory. Each is straightforward but adds 30 to 60 minutes of labor.
Heat-pump and two-stage systems need thermostats specifically rated for that equipment. Putting a single-stage thermostat on a two-stage furnace works but you lose the staging capability and pay for it in both comfort and efficiency.
SMUD runs periodic rebates on qualifying smart thermostats that can offset $50 to $100 of the purchase price — check the current rebate catalog before scheduling the install.