So you thought that by investing in a Nest ‘smart’ thermostat, you’d always come home to a nice, warm home, and save money on your fuel bills?

Well, it looks like the latter is true for many Nest users whose thermostats have been updated to software version 5.1.3 or later, according to Nest. Because their thermostat has become “slow, unresponsive, or won’t turn on”. In other words, their expensive ‘smart’ system has stopped working, and with it their heating.

Nest’s support article describes a long series of steps that you can follow to try to fix the problem, but it is one familiar to many who have used battery-powered devices with power-management features: following the software update, some Nest thermostats are running their batteries flat very quickly indeed.

This problem can affect all three generations of Nest Thermostats, and apparently Nest is ‘working on a fix’ for the bug.

Nest claims that it has sorted the problem already for “99.5%” of all users, but that still seems like an awful lot of very cold homes. It is also worrying that the flawed software update should have been rolled out in the middle of the winter in the northern hemisphere – hardly ideal timing.

It highlights a problem which is likely to plague Nest and IoT users in the future: as any failure in the Nest Thermostat brings the whole heating system to a halt, good engineering design would require either a fail-safe operating mode, or a backup system. Once the Nest’s battery power is too low for the thermostat to function, there is no low-power fallback system. The only real solution is to keep a traditional thermostat and control clock ready in case your Nest is out of action for more than a few hours.