Nest has been a Google brand since 2014, and two families are on the walls we visit. The Nest Learning Thermostat is the round metal-ringed one with a built-in rechargeable battery. The lower-priced Nest Thermostat, released in 2020, has a mirrored face and runs on two AAA batteries alongside the power it takes from the system wires.
Google's own guidance is that Nest thermostats work without a C-wire in most homes, and in many they do. The houses where they do not are the ones we get called to: a furnace board that reacts to the trickle of charging current, or a system that runs so little in spring and fall that the battery never tops up. Adding a common ends the problem for good.
One change owners of early units should know about. Google ended support for the first and second generation Nest Learning Thermostats on October 25, 2025. They still control heating and cooling from the wall, but they no longer connect to the Nest or Google Home apps, so remote control and Home/Away features are gone.
People also ask about a Nest rebate in Ontario. Smart thermostats are part of the Home Renovation Savings Program; the amount and the eligible models are on the program page, and our smart thermostat rebate summary links to it. We install Nest thermostats as an independent contractor and make no claim about any installer program Google runs.
Google Nest lines we install and service
The current flagship, with a larger display and a wireless temperature sensor for a second room. It builds a schedule from how you adjust it in the first weeks, which works well in a house with regular hours and badly in one without.
The model on most walls. It has ten terminals including a star terminal that can be assigned to a humidifier, a dehumidifier or another function. Its battery is sealed inside, so a unit that will not hold a charge on a good power supply is replaced, not repaired.
The mirrored, lower-priced model. It has fewer terminals than the Learning Thermostat and no learning schedule. Check it against your equipment before buying if you have a second heating stage, a humidifier or a hybrid heat pump.
The discontinued frosted-white model, still supported by the app. It also has a reduced terminal set, which is the usual reason one gets replaced when a house moves to a heat pump.
Out of software support since October 2025. They work as a manual and scheduled thermostat at the wall only. If app control matters to you, the answer is a new thermostat; nothing can be done to the old one to bring it back.
What goes wrong on Google Nest equipment
Low battery, Wi-Fi drop-outs and a chattering furnace board
These three symptoms share one cause, a missing C-wire: the Nest pulses current through the heat or cool circuit to charge itself, and some furnace boards read those pulses as a call, clicking a relay or starting the inducer for a second. When the battery sags anyway, the thermostat shuts off its Wi-Fi to save power. Running a common from the furnace, or fitting a Nest Power Connector there, gives it steady 24 V and stops all three. Google flags the same thing with the N260 message.
E73, E74 or E195: no power to the Rc, Rh or R wire
Google treats E codes as critical: the thermostat will not run heating or cooling until the power returns. In summer the usual cause is a condensate float switch that has opened because the AC drain is blocked. In any season it can be a blown fuse on the furnace board, a furnace door off its switch or a tripped breaker. Replacing the thermostat fixes none of these; our page on Nest error E195 covers the safe checks, and the full Nest thermostat error codes guide lists the rest.
Heat pump blows cold in heat mode: O/B orientation
A Nest assumes the reversing valve is energised in cooling (O), which suits most heat pump brands. A few energise it in heating (B), and on those the default setting swaps the modes. It is a one-line change in the equipment settings. Dual-fuel systems, a heat pump with a gas furnace, need more care: compatibility differs by Nest model, and the changeover has to be set so the two heat sources never run together.
A wire the Nest does not detect
Nest bases use push-in connectors. A conductor that is too short, bent or corroded will sit in the hole without pressing the tab down, and the thermostat then behaves as if that wire is not there: no heat, no fan, or no cooling. Stripping back to clean straight copper and reseating it fixes this. Why a Nest will not turn on the heat goes through the other causes.
Google Nest warranty: what to know
- Google is the warrantor, and the limited warranty term differs by model and by where the thermostat was bought. Check Google's warranty page against the model on your box.
- Google publishes an Extended Pro Warranty for eligible Nest products bought from and installed by an enrolled Nest Pro. It applies only through that program, so confirm an installer's status before counting on it.
- First and second generation Learning Thermostats are past both warranty and software support.
- The warranty covers the thermostat. A furnace fuse, a float switch or a control board affected by a wiring mistake is outside it, as is installation labour.
Parts availability in the GTA
A Nest is two pieces, the base on the wall and the display that clips onto it, and neither is serviced at component level. When one fails the thermostat is replaced. The accessories are readily available at GTA retailers: the Nest Power Connector, the trim plate for covering an old thermostat's footprint, and the temperature sensors for the Learning models. As with every smart thermostat, the parts that solve most Nest faults belong to the furnace or air conditioner, and those are generic items.
Nest Thermostat Error Codes Explained — what each one means and whether it is safe to keep running.
Common questions
Is there a Nest thermostat rebate in Ontario?
Smart thermostats are included in the Home Renovation Savings Program, delivered by Enbridge Gas and Save on Energy. The official pages do not all show the same amount, so we do not quote a figure: read the program page for today's number, the eligible models and whether approval is needed before purchase. The Canada Greener Homes Grant, which some older articles still mention, is closed to new applicants.
Do I need a C-wire for a Nest, or is the Power Connector enough?
Either one gives the thermostat constant power. A true C-wire is the cleaner answer when a spare conductor already exists in the cable. The Nest Power Connector installs at the furnace or air handler and needs no new wire in the wall, which suits finished basements. It works on 24 V systems with the Nest models Google lists as compatible, so check yours first.
Can I keep using my first or second generation Nest?
Yes, as a wall thermostat. It will hold a temperature, follow its schedule and switch modes when you turn the ring. It will not appear in the app, respond to voice assistants or use Home/Away features. If the battery is also failing after more than a decade, replacement makes more sense than adding a common wire to it.
Why does my furnace click or short-cycle since the Nest went in?
The thermostat is charging itself through the heat wire, and the furnace board is reacting to it. This is hard on relays and igniters over a season, so do not leave it. A common wire or a Power Connector stops it. If short-cycling continues afterwards, the cause is in the furnace, and why a furnace keeps short-cycling explains what to look at.
What does Nest installation cost?
The price follows the wiring. A swap on a cable with a common is a short job; adding a Power Connector, running a common or configuring a heat pump adds time and is quoted in writing first, as our smart thermostat installation page explains. A Nest that is already installed and showing a power error is a diagnostic call, $90–$150, folded into the repair if you go ahead with it.