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If your Google Nest is not heating hot water, first check whether your model and installation are meant to control it. Hot-water control is not available on every Nest: it usually applies to a 3rd-generation Nest Learning Thermostat wired to a separate hot-water cylinder. If your system is compatible, a temporary boost can help show whether the problem is the schedule, the Heat Link, or equipment such as the boiler or cylinder valve.
This guide focuses on UK and European boiler-and-cylinder installations. North American Nest thermostats generally control HVAC equipment rather than a UK-style hot-water cylinder.
First, check whether your Nest can control hot water
Nest hot-water control depends on the thermostat model, boiler, installation wiring and setup. The quickest clue is whether the thermostat or app has a Hot water tile, schedule or boost option.
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|---|---|
| 3rd-generation Nest Learning Thermostat, correctly installed | Yes, with simple on/off control |
| Nest Thermostat E with a separate cylinder | No |
| 2nd-generation Nest Learning Thermostat | No |
| Combi boiler | Usually no tank-style schedule; hot water is heated on demand |
| OpenTherm boiler | Controls vary by boiler and installation; check compatibility for the exact model |
Google’s hot-water compatibility guidance lists supported combinations. Even a compatible thermostat may have no Hot water controls if it was installed to control heating only. A separate programmer may therefore still be controlling the cylinder.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Connectivity : Wi-Fi - 802.11b/g/n 2.4 GHz, 802.11a/n 5 GHz Wi-Fi., Wireless interconnect : Bluetooth Low Energy Please refer to the product description section below for all applicable legal disclaimers.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home. Lock feature: No
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
With a combi boiler, a Nest may control aspects of boiler operation where supported, but that is different from scheduling a tank. If you have a cylinder and no Hot water controls, do not assume the thermostat is faulty: the controls may not have been connected or configured for it.
Run a temporary boost test
A boost asks the system to heat water outside its regular schedule. It is a useful diagnostic, but a displayed “on” state does not prove that the boiler fired or that hot water circulated to the cylinder.
Google Home
- Open Google Home and tap Home.
- Tap Climate, then select your thermostat.
- Tap Hot water.
- Choose 30 min, 1 hr or 2 hr, then tap Start boost.
Nest app or thermostat
In the Nest app, select Hot water, tap On, then Start. On the thermostat, press the ring, choose Hot water, select a duration and press the ring to start. Labels can vary slightly by model and software version. Google documents these controls in its hot-water schedule and boost instructions.
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Read the result
- Boost works, but the schedule does not: check whether the schedule is enabled, has an active period for today, and uses the correct time and day. Away behaviour may also have suspended scheduled heating.
- The app changes state but the Heat Link does not react: check Heat Link power and connection, and note any thermostat help code. The installation or control signal may need attention.
- The Heat Link reacts, but the boiler or cylinder does not heat: the Nest may be issuing a call correctly; investigate the programmer, boiler, valve, cylinder thermostat or other downstream controls.
- Hot water comes on only with central heating: this can point to a wiring, valve or control-configuration problem. It does not identify a particular failed part.
A quiet boiler response is not conclusive if the tank is already at its target temperature. Allow for the system’s normal response time and check whether the cylinder actually warms.
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- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills[2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
Check the schedule, clock and away settings
In Google Home, the documented path is Home → Climate → thermostat → Settings → Hot water → Schedule. Confirm the schedule is enabled and includes a heating period at a time that has not already passed. Check the day, current time, start and end times, and repeat days. On the thermostat, look under Settings → Hot water schedule for options to enable, disable or edit it. App and firmware wording can vary.
Google says scheduled tank heating can stop after the home has been detected empty for at least 48 hours, then resume when someone returns. If the problem began after a holiday or extended absence, check the thermostat’s away settings:
- Google Home: Home → Climate → thermostat → Settings → Hot water.
- Nest app: Hot water → Settings → Home/Away Assist.
Look for Eco when away or equivalent behaviour. It is not a universal rule that hot water always turns off whenever the home is empty; the setting and system behaviour matter.
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Also check whether water is already at its configured target. A simple on/off cylinder setup may let Nest schedule heating without letting you set the water temperature. Google documents a minimum tank-temperature setting of 55°C (131°F) to help reduce Legionella risk; follow the product’s guidance and do not lower a safety-related setting to mask a heating fault. See Google’s hot-water guidance.
Rank #3
- Nest’s smartest, most advanced thermostat yet, the Google Nest Learning Thermostat (4th gen) is a beautiful, brilliant way to save energy, keep your home comfortable, and help make sure your heating and cooling systems are running smoothly[4]
- Savings you can count on: The Nest Learning Thermostat can help save up to 31% on heating and cooling bills [2]
- Improved compatibility: It works with most 24V systems, including gas, electric, oil, forced air, heat pump, and radiant, and no C wire is required for installation in most homes; visit the Nest Compatibility Checker for more info[5]
- Easy control in the Google Home app: Adjust on your phone from anywhere[1] or by using your voice with Alexa, Siri, or Google Assistant smart speaker[3], it’s easy to install yourself and it’s Matter compatible for simple integration into your smart home[5]
- Beautiful design: With a 60% larger display[11] and Dynamic Farsight, you can see info from across the room[1]; choose the design, like a clock or the weather; it automatically adjusts brightness for the best readability or you can adjust manually
Check the Heat Link and any existing programmer
On European installations, the Heat Link is the control unit between the Nest and the heating equipment. Note whether it has power, whether its status changes when you start a boost, and whether the thermostat reports a connection problem. A light change or relay response shows only that part of the control path reacted; it does not prove the valve opened or the boiler completed the heating cycle.
For temporary manual control, Google’s model-dependent procedure is:
- Nest Thermostat E: press the Heat Link button twice to turn heating on or off.
- 2nd- or 3rd-generation Nest Learning Thermostat: press the button once.
If the system controls a domestic hot-water tank, manual heating also turns on the hot water. Manual mode stays on until switched off and does not follow the normal schedule. Treat it as a temporary diagnostic or emergency measure, not a repair. See Google’s manual Heat Link instructions.
A separate programmer may remain part of the system even after Nest is installed. Check that its hot-water channel is on or set to the appropriate automatic mode. Some installations replace the old programmer; others integrate with it, so do not remove or disable it based on assumption. Google explains the options in its programmer installation guidance.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Control the temperature with your voice using smart home devices that work with Google Assistant or Alexa[3]Nest Renew makes it simple to support clean energy right from home; it works with your Nest Thermostat[5] to help you automatically prioritize your usage[6] to times when energy is cleaner or less expensive.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory. You can control your Nest Thermostat manually when there's no internet connection.
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]. | Control the temperature with your voice using smart home devices that work with Google Assistant or Alexa[3].
What the symptoms can tell you
No Hot water option in the app or thermostat
Check the thermostat model and boiler type first. The model may not support a cylinder, the system may be a combi, or the Nest may have been configured for heating only. The original programmer may still be responsible for hot water. If a compatible model is supposed to control a cylinder, an installer can confirm whether the hot-water circuit was connected and set up.
Heat Link reacts, but the water stays cold
The fault may be beyond the Nest command. Possible causes include a motorised zone valve or actuator that is stuck or failed, a cylinder thermostat that is faulty or misreading temperature, a boiler lockout, a pump or circulation problem, or a fault in the programmer or wiring centre. These symptoms suggest possible causes rather than proving which component has failed.
The boiler fires, but the cylinder does not warm
This points toward heat not reaching or circulating through the cylinder. A valve that does not open fully, a sensor or cylinder thermostat problem, a boiler-control issue, circulation trouble, scale, or a tank or plumbing fault may be involved. A heating engineer can diagnose the equipment safely; a thermostat reset will not repair these faults.
Heating works, but hot water does not
Heating and hot water may use separate control circuits, relays and valves. If heating works but a boost does not, focus on the hot-water side: the separate programmer, Heat Link hot-water output, cylinder thermostat, motorised valve and associated controls. An engineer should inspect any suspected wiring or control fault.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page.Connectivity Protocol : Wi-Fi.Connectivity Protocol : Wi-Fi
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory. Lock feature: No
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home; easily program an energy efficient schedule in the Google home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
- Savings Finder looks for more ways your thermostat can help you save, and suggests tweaks to your schedule in the app; check with your energy provider to learn more about rebates and more ways to save on a Nest thermostat
Both heating and hot water fail, or Nest reports a connection problem
Check that the thermostat display is seated and that the Heat Link appears powered. Record the exact help code and whether the thermostat is online. Google’s Heat Link and thermostat help-code guidance covers connection and power problems. Manual Heat Link control may provide temporary operation while the cause is investigated.
Keep electrical checks safe
You can check app settings, note status lights, confirm that the thermostat display is seated, and check whether an external switch or programmer appears to be on. Do not open the Heat Link, boiler, wiring centre or electrical control box, probe live terminals, bypass a valve or move relay wires unless you are qualified to do so. Boiler controls can contain mains voltage.
Loose, corroded, incorrectly inserted or incompatible wiring can cause problems, but tracing it is not a safe trial-and-error task. Nest wiring requirements vary by system; Google’s references cover wire detection and compatibility and incompatible wiring. Ask a qualified installer or electrician to assess wiring and mains-voltage faults.
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Do not start with a factory reset. A reset can remove configuration and require setup again, but it cannot fix an incompatible system, failed fuse, incorrect relay wiring, stuck valve, boiler fault or failed cylinder thermostat. If you restart or reset, first record your schedules and settings, and use Google’s instructions for your specific model. If the Nest displays a help code or the Heat Link is disconnected, follow the relevant connection procedure before changing configuration.
Who to call, and what to tell them
- Nest Pro or qualified installer: hot-water controls are missing on an installation that should support them, the Heat Link does not respond, or the wiring and setup are uncertain.
- Heating engineer: the Heat Link responds but the boiler, valve, cylinder thermostat, pump or cylinder does not heat correctly, or the boiler shows an error.
- Qualified electrician: there is a suspected mains-wiring or electrical control fault, or signs of unsafe wiring.
Before calling, note the Nest model, boiler model, whether there is a separate cylinder, whether heating works, what happens during a boost, the Heat Link’s light or response, any help code, the programmer’s setting, and when the problem began. Mention whether it followed a power cut, service, rewiring, router change or app migration. This helps distinguish a Nest setup issue from a boiler or cylinder fault.
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