Skip to main content

How to turn OFF the pre-heat on your Vaillant combi boiler to save 5-10%


Jo Alsop

Heating Hero

The Heating Hub

Bespoke instructions for turning off the pre-heat on any Vaillant combi boiler to save 5-10% on your gas bill.


You can save around 5-10% on your gas bill if you turn the 'pre-heat' off on your Vaillant combi boiler

Some boiler manufacturers provide a 'hot water pre-heat' facility on their boilers. This is designed to cut down the time it takes for hot water to come out of the taps but keeping some hot water ready in the boiler.

The boiler will fire every 30-90 minutes and uses small amount of gas each time, but over the year it'll can add up to 500-750kWh of wasted heat depending on when you're home. This is around 5-10% of the average household's gas bill. 

In this blog we cover turning off Vaillant pre-heats (referred to at Warm Start or Comfort mode). Vaillant make life very simple for turning off pre-heats! You will either have a boiler with buttons or a boiler with buttons and two dials. Instructions for each below. (If you also have a programmer on the front of your boiler this will present a dial in the middle of the boiler - ignore it!)

If wait times are a real problem for you, we recommend you fit a device called a combi save instead. This restricts the water passing through the boiler until the water has reached temperature. It saves both gas and water!


  1. Vaillant combis with buttons
  2. Vaillant combis with buttons and two dials on the left hand side.


1) Vaillant combi boilers with buttons

If the letter ‘C’ is showing in the display, 'Comfort mode' is on, which means the Preheat is switched on. To switch off: press the left hand ‘i’ button labelled ‘4’ on the diagram above. Then press the the right hand ‘i’ button and ‘Comfort on’ or 'Comf. on' will flash in the display. Press + button to change to 'Comfort off' or 'Comf. off' and press the right hand ‘i’ button to confirm the change.



2) Vaillant combi boilers with dials and buttons

Turn the hot water dial down (top dial with tap icon) to minimum and leave for 5 seconds. Turn up again, but no higher than 59degC or the preheat will come back on. NB 'comfort mode' is referred to as 'warm start' in earlier models.



Can't find your boiler?

It is definitely a combi boiler? It will be a combi boiler if you do not have a hot water cylinder. If it is a combi boiler and your model is not showing it is likely that your model does not have a preheat option.


Jo & Caroline - Heating Heroes

1-2-1 advice with our Efficiency Audit

Get the whole package of efficiency upgrades with our bespoke advisory service

More reads...

Guide to boiler efficiencies

99% of gas boilers are running below their A-rated efficiency, we explain how.

Learn more

The real cost of boiler inefficiency

Soaring gas prices expose the real cost of poorly performing boilers.

Learn more