Smart Thermostat Time-of-Use Automation Study

This report presents the results of PG&E’s Smart Thermostat Time-of-Use (TOU) Automation Study with a bring your own thermostat program design. The study provided incentives to residential customers who allowed PG&E to reduce or shift their electricity use in the 4–9 pm peak hours by communicating with WiFi-enabled smart thermostats. In 2021, PG&E tested three types of connected thermostats – Nest, Ecobee, and Emerson – that reduce or shift electricity during demand response (DR) events. In addition, two thermostat manufacturers – Ecobee and Emerson – also allowed customers to automate daily response to TOU rates.

The study launched mid-summer, and PG&E recruited 11,320 residential sites with 13,744 controllable thermostats by September 30, 2021. The dispatchable events analysis relied on randomized control trial where treatment and control sites were randomly assigned for each event. PG&E called a total of 14 events over the course of half a summer. By design, PG&E called events over a wide range of weather conditions, event start times, and even event durations. The dispatchable event impacts were estimated using whole-home hourly data and a difference-in-difference panel regression. The daily TOU automation analysis included over 3,600 and was analyzed using a matched control group and difference-in-differences. The control group was selected from a pool of ecobee participants without TOU automation using propensity score matching.