How Thermostandard reads a thermostat

Statements, word for word

Each product page is one model, with its model number. The compatibility facts on it (C wire, systems, stages, heat pump support, auxiliary heat, voltage, maximum load, poles, sensors and connectivity) are what that model's own listing or maker page states, kept on file with the passage they came from.

Where a maker doesn't state something, the page shows 'Not stated'. A sister model's figure is never borrowed, because a basic and a premium version of the same thermostat can differ on exactly the wiring point that matters.

Conflicting listings

A listing sometimes says one thing in its title and another in its details, for example 'no C wire needed' in a headline and 'C wire required for heat pumps' further down. We show the more restrictive statement and keep the listing's wording, so nobody buys on the optimistic half of a contradiction.

How the checkers decide

• Wiring checker: a thermostat is left out only when its maker's statement rules out the system your wires describe. If the listing is silent on a point your system needs, the thermostat appears under 'check with the maker', never as a match.
• Thermostats whose makers require a C wire stay visible when you don't have one, in their own group, because an adapter or spare wire often solves it.
• Line-voltage load checker: current = heater watts / circuit voltage, compared with the maker's stated maximum. Where a maker gives watts only, the rating is converted at the highest voltage it lists.

Savings figures

Energy-saving figures are quoted from their source, usually ENERGY STAR's smart thermostat criteria and FAQ, and labelled as averages. We don't promise any household a saving.

Lists

Each ranking states its order: by a stated compatibility feature, or in an editor's order for a stated purpose, with a reason written for each pick.

Updated October 2026.