What they do

A smart thermostat is three things: a programmable thermostat (which has existed since the 1980s), a Wi-Fi remote control, and some learning algorithms. The savings come almost entirely from the programmable part. The Wi-Fi and learning are nice-to-have.

Claimed savings: 10-23% on cooling and heating. Actual savings for most Texas households: 5-15%.

When they save money

  • Your house is empty 8+ hours a day and you currently keep the AC at a single temperature. This is the big one. Setback from 74°F to 80°F during work hours saves 10-18%.
  • You never consistently set back a dumb thermostat manually. Most people don't. Smart thermostats remove the friction.
  • You have an HVAC system with sensors the smart thermostat can optimize. Multi-stage systems benefit more than single-stage.

When they don't save money

  • Someone is home all day. Work-from-home, retirees, families with young kids — no meaningful "away" window = no setback savings.
  • You already use a programmable thermostat with a reasonable schedule. Then the smart thermostat mostly just adds convenience.
  • Texas August. Setback savings diminish when the temperature gap between "away setpoint" and outdoor temp is small. If it's 100°F outside and you set to 85°F away vs. 74°F home, the AC runs nearly constantly either way — the savings is about letting the house get warm, not reducing runtime dramatically.

The setup that matters

Out of the box, a smart thermostat isn't doing much. To unlock the savings:

  1. Set a real schedule with distinct "home," "away," "sleep" setpoints. Don't rely on the defaults.
  2. Configure geofencing to detect when everyone's gone. Without this, smart scheduling falls back to time-of-day guesses.
  3. Pair with utility demand-response programs where available. Some Texas TDUs offer $25-75 credits for letting the thermostat adjust during peak events.
  4. Check the comfort gap. A thermostat at 72°F running constantly isn't the thermostat's fault — it's a sign of undersized or inefficient AC.

Which ones

The three mainstream options (Nest, Ecobee, Honeywell) all save roughly the same amount on energy. Differences are UX, learning algorithms, integration with smart-home platforms. If you're not deep into smart home, a Honeywell T9 or Ecobee 3 Lite at ~$150 is plenty. Nest Learning is the premium option at $250.

Payback math

Average Texas household with AC: ~1,800 kWh cooling/year × 10% savings × 12¢/kWh = $22/year. $150 thermostat = 7-year payback on energy alone. Plus demand response credits ($25-50/year), occasionally a utility rebate ($50-100). Realistic payback with rebates: 2-4 years.

Honest take: buy one for convenience and automation. The energy savings are real but modest. If you're buying specifically to save money, the payback is fine but not exciting.