Do touchscreen thermostats need a C-wire?

Question

Accepted Answer

Most smart touchscreen thermostats prefer a C-wire (common wire) for continuous power. Some models like the Sensi Touch work without one using battery backup. The Nest uses a rechargeable internal battery. If you do not have a C-wire, the Sensi Touch is the safest choice — or have an HVAC tech add one for $50-100.

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