Nest thermostat: H2, H72 or H152: the thermostat lost power
Your thermostat has lost power.
Applies to: Nest Learning Thermostat and Nest Thermostat E with a Heat Link. What you see: a code.
Codes this page covers: H2 H72 H152.
What Google says to do
Wiring and power. Google ties this, on at least some systems, to the wiring, the power supply or the C wire. The steps here are only Google’s own, as its page states them; semiatic gives no wiring instructions of its own. Google’s own line on calling a professional is step 4 below.
- Google says that on a stand, the Nest power cable should be fully in the plug, the plug pushed all the way into a switched-on wall socket, and the socket tested with a lamp; it recommends a socket not controlled by a wall switch.
- Google says that on the wall, the display must be fully attached to its base; push it down until it clicks.
- Google says to check the fuse that controls power to your system with the power turned off first, re-seating or replacing it as necessary and following the manufacturer’s manual for safety precautions.
- Google says that if you still can’t fix it, contact a local pro.
Source
Google’s own help page, read on the date shown.
- Google Nest Help: Troubleshoot Nest thermostat help codes — Nest Learning Thermostat (1st to 4th gen), Nest Thermostat E and Nest Thermostat; H codes only where a Heat Link is installed. support.google.com Checked 2026-09-29.