The short version: The 3rd generation Nest Learning Thermostat (2015) is the classic round metal-and-glass Nest — Stainless Steel, Copper, or Black finishes, auto-schedule learning, and Farsight. It’s now an older design competing against Google’s own 4th-gen redesign, and at $220–250 it doesn’t always undercut current-generation stock by much. It still works well, but check pricing against the newer model before assuming it’s the budget option.

Who It’s For

Works with central forced-air heating and cooling: gas furnaces (single- and multi-stage), central AC, and standard-to-moderately-complex heat pump systems. It does not work with electric baseboard heat.

Best fit for:
– Buyers who specifically want the classic round steel/copper/black Nest look, discontinued in the current 4th-gen redesign
– Google Home households that want auto-scheduling without paying 4th-gen pricing, if a good deal is available
– Anyone replacing an existing 3rd-gen unit and wanting matching hardware/finish across rooms

Skip it if you want the newest sensors and AI-driven scheduling, or if similarly-priced new 4th-gen stock is available — the design departure in the 4th gen is substantial enough to be worth comparing directly.

Design & Build

The 3rd gen has a 3.25-inch color display in a circular metal housing, available in Stainless Steel, Copper, and Black finishes. Farsight lights up the display as you approach from across the room — a feature the base Nest Thermostat lacks, and one reviewers consistently call out as a nice, non-essential touch.

It’s a distinctive piece of wall hardware; the design has aged well even as Google has since moved to a different, larger-bodied design in the 4th gen.

Setup & Compatibility

C-wire situation: No C-wire required — the 3rd gen uses the same power-harvesting approach as other Nest models, drawing a small charge from your HVAC system to maintain its battery.

System compatibility: Handles single- and multi-stage gas furnaces, central AC, and heat pump wiring including the O/B terminal for reversing valves and auxiliary/emergency heat. It’s a mature, well-tested compatibility list at this point.

Known install-related complaints: Some buyers have reported a “W5 error” that prevents Wi-Fi connection on a subset of units — Google has historically replaced affected devices under warranty. A number of reviewers have also noted that the in-box install directions are thinner than they’d like, though the app itself walks through wiring reasonably well.

App & Ecosystem

The auto-schedule learning is the model’s signature feature: it observes your manual temperature adjustments for the first one to two weeks and builds a schedule from the pattern. It works best for households with consistent routines; irregular work-from-home schedules can trip it up, requiring more manual overrides than you’d expect from a “learning” thermostat.

Ecosystem support:
– Google Assistant / Google Home: Full native integration
– Amazon Alexa: Supported
– Apple HomeKit: Not supported — a persistent Nest limitation across all generations

A commonly cited flaw involves the optional remote Nest Temperature Sensor: several reviewers and owners describe its response time as slow enough that HVAC runs noticeably past the target temperature before the system catches up. If precise room-by-room comfort matters to you, this is worth weighing against Ecobee’s SmartSensor system.

Should You Buy 3rd Gen or Wait for 4th Gen Pricing to Drop?

The 4th-gen Learning Thermostat (2024) is a genuinely different product: larger glass display, a redesigned base, bundled temperature sensor on some configurations, and Matter support. If new 3rd-gen stock is priced close to 4th-gen stock, the 4th gen is usually the better buy for anyone not specifically attached to the classic steel/copper/black look. The 3rd gen mainly makes sense when it’s meaningfully cheaper or you specifically want the older aesthetic.

Price & Value

Nest Learning Thermostat (3rd Gen)
Price (USD) $220–250
Warranty 2 years
Subscription required No

Sold through Best Buy, Home Depot, and Amazon, generally as remaining/clearance stock rather than a current Google product line. See Smart Thermostat Rebate by State for rebate eligibility — it’s ENERGY STAR certified and typically appears on most utility qualifying lists, though amounts vary too much to state generally here.

Pros & Cons

Pros:
– Distinctive, well-regarded design in steel, copper, or black finishes
– Farsight display activation
– Auto-schedule learning works well for consistent routines
– Mature, well-tested HVAC compatibility

Cons:
– Older design now sitting alongside a substantially redesigned 4th-gen model
– No Apple HomeKit support
– Remote sensor response time criticized as slow by multiple reviewers
– A subset of units affected by a Wi-Fi connection (“W5”) error
– 2-year warranty, shorter than Ecobee’s 3-year

Nest models compared: Nest Thermostat, Nest Learning Thermostat (3rd Gen), and Nest Learning Thermostat (4th Gen), with features, price, and rebate eligibility

The Recommendation

Buy the 3rd Gen Learning Thermostat if you specifically want the classic steel/copper/black design and it’s priced meaningfully below current 4th-gen stock.

Buy the 4th Gen instead if pricing is close — you get a newer design, bundled sensor options, and Matter support for roughly the same money.

Consider Ecobee if HomeKit support or precise room-sensor performance matter more to you than the Nest aesthetic. See Nest vs Ecobee: Which Should You Buy?

Frequently Asked Questions

Is the 3rd Gen Nest Learning Thermostat still worth buying over the 4th Gen?
Only if it’s noticeably cheaper. The 4th gen is a newer design with more current sensor tech; the 3rd gen mainly wins on price when stock is discounted or on aesthetic preference for the classic look.

Does the 3rd Gen support Apple HomeKit?
No. No Nest generation, including the 4th gen, supports HomeKit.

What’s the “W5 error” some owners report?
A Wi-Fi connectivity fault reported on a subset of units that prevents the thermostat from joining your network. Google has historically replaced affected units under warranty — contact support if you experience it.

Does the 3rd Gen work with heat pumps?
Yes, including standard and dual-fuel setups via the O/B terminal and auxiliary/emergency heat controls, though Ecobee offers more granular controls for complex systems.

Is the remote Nest Temperature Sensor worth adding?
It works, but multiple reviewers note its response time lags behind the room’s actual temperature change, which can mean the HVAC overshoots the target before the sensor catches up.

Does the 3rd Gen require a C-wire?
No, it uses power harvesting like other Nest models, though connecting a C-wire if available eliminates any risk of ghost calls.