Last updated: 16/10/2022

Welcome to our big gas boiler test 2022. Here we present all the gas boilers we have tested in detail. We have compiled detailed background information and added a summary of customer reviews on the web. We would like to make your purchase decision easier and help you find the best gas boiler for you.

You will also find answers to frequently asked questions in our guide. If available, we also offer interesting test videos. Furthermore, you will also find some important information on this page that you should definitely pay attention to if you want to buy a gas boiler.


  • A gas boiler is a type of continuous flow heater that allows you to heat your living space. Aspects such as cost, performance and maintenance play a role.
  • You can mount a gas boiler on the wall in the bathroom or on the floor. There are also combination boilers that combine many functions.
  • With a gas boiler, you have long-term advantages that save you a lot of money on heating and hot water

The Best Gas Boiler: Our Choices

Guide: Questions you should ask yourself before buying a gas boiler

What is a gas boiler?

When you think of a gas boiler, synonyms like bathroom, heating, boiler or hot water come to mind. Basically, a gas boiler has something to do with all these synonyms. Gas boilers are very widespread in Germany and you probably have one in your flat or house. Basically, this term is applicable to several types of appliances. The work that a gas boiler does is to produce hot water or, more precisely, to heat water by burning gas.

The water is pumped from the mains into the house and into the gas boiler. The gas boiler distributes the necessary hot water in the flat or house to the necessary suppliers, the heating system. You can buy a gas boiler both with and without a storage tank, which makes it suitable for universal use. Gas boilers can not only heat individual flats, but can also supply entire family homes, depending on the type and device.

As a tenant, you will not have to take care of such a flow heater yourself, as this is the landlord’s business. You may have to make an effort to have the gas boiler in your flat cleaned or serviced regularly. You should call a professional to do this.

How does a gas boiler work?

The burner of a gas boiler is probably the most relevant component of the appliance. Unlike a gas heater, the water is not pre-heated and held in a necessary storage tank. The gas boiler only works on demand, which means that it only starts working when you turn on the heating.

The burner only starts its process when the heating system sends a signal that it needs hot water for heating. The gas boiler usually works with liquid and natural gas. In the case of drinking water, the gas boiler can provide a hygienic advantage because it always heats the water fresh and transports it to the tap. On the other hand, it can also be overloaded if all the radiators and taps are in tact.

At what prices is a gas boiler available?

The price range among gas boilers can be relatively different. The fact that gas boiler prices are already in the four-digit range is no guarded secret. Yes, they are extremely expensive, but as a tenant it is not your duty to purchase them at your expense.

Nevertheless, it shouldn’t hurt to know what the price ratios look like. Prices can vary from manufacturer to manufacturer, but the type of gas boiler can also play a role. Gas boilers are not only available for hanging or mounting on the wall, but also for standing firmly on the floor, as in the case of heat pump heating.

Model Price
Wall-mounted gas boiler 1700 – 2800€
Floor-mounted gas boiler 2600 – 5000€
Combi boiler 2500 – 3000€
Wall-mounted gas boiler 2000 – 3500€

How much does it cost to install the appliance?

If you want to dispose of your old appliance, there may be additional costs for the installation. With some manufacturers, products from the more expensive class may hardly require any installation costs.

However, installation costs usually range from 1200 to around 2000€. If there is no gas connection, the installation costs can range from 1500 to 2500€. The prices are intended as a guide, but they can of course vary.

Who are the best-known manufacturers of gas boilers?

Not everyone is directly familiar with gas boiler manufacturers, but most of them are produced by big names. Some of them should be familiar to you. Here we have a list of the most relevant gas heater manufacturers.


The company from the Rhineland is probably the best-known brand among radiators and gas boilers. Vaillant has been in existence since 1874 and offers a wide range of modern heating, ventilation and air-conditioning technology. Buyers can enjoy a wide range of products from the manufacturer’s portfolio, which constantly features new innovative technology.


The company from Germany was founded in 1895 and is now run by the Bosch Group. Today, it is known for its qualitative products with attractive prices.


Buderus is also a brand or manufacturer that today belongs to the Bosch Group. They are also active in thermotechnology, from oil/gas boilers and heat pumps to solar energy, their ranges include. With Buderus, you can rely on modern technology and will have easy access to spare parts.


Viessmann is a lesser known company that has been around since 1917. They offer products and services such as boilers, solar heating, heat pumps, air conditioning, ventilation and many more. They are particularly known for the quality and durability of their products.

What alternatives are there to the gas boiler?

Operation by gas heating may appear to be the cheapest option in the first place, but there are certainly some more or less relevant disadvantages hidden behind it. In a small flat, the gas boiler can lead to a lack of space in the bathtub or wherever the heater is located.

The electric version, on the other hand, saves a lot of space, but it can end up costing you more than gas. Here we have a list of relevant ways you can heat your home.

Heating technology Description
Pellet heating The fuel from the storage room is fired and the heat is distributed in the house. Converting to pellet heating is expensive, but the fuel is very cheap. They heat almost CO2-neutral.
Water pump Water pump collects heat from the air, earth or water and brings it into the house for heating. Heat pump is particularly suitable for a well-insulated house and can be combined well with underfloor heating.
Oil Oil is the rare way to heat in Germany. Prices and costs are related to oil and crude prices. A good oil condensing boiler can save up to 40% on heating costs, but the installation can cost more than 4000€.

Decision: What types of gas boiler are there and which is the right one for you?

A gas boiler can differ according to its installation or even according to its type itself. The most relevant types of gas boiler are the following:

  • Wall-mounted boiler
  • Floor boiler
  • Combi boiler
  • Heat centres

Depending on the type of house or flat you live in, your decision may be guided. Everyone decides for himself or herself which factors are most important to him or her. Most Germans favour the wall-mounted gas boiler. In the following, the four types are explained in more detail to make your decision easier.

What is a wall-mounted boiler and what are its advantages and disadvantages?

Wall-mounted boilers are ideal for flats or detached houses. They can be more or less space-saving, but in a cramped bathroom they can take up a lot of space. With an integrated storage tank, they provide a high level of hot water comfort. You can buy wall-hung boilers both with and without a storage tank.

They are cheaper to buy than floor-standing gas boilers. However, unlike floor-standing boilers, the entire appliance is affected in the event of a failure,

  • cheap in comparison
  • space-saving
  • parts easy to replace
  • Gas prices are rising
  • overloaded with several radiators

What is a floor-standing gas boiler and what are its advantages and disadvantages?

Floor-standing gas boilers generally take up more space and are therefore usually located in the basement. Although they are more expensive to purchase than classic wall-mounted boilers, they can supply more floors, radiators or houses due to their performance.

Since they usually serve larger areas, they appear in conjunction with storage tanks, as they can otherwise be easily overloaded. They are comparatively larger and weigh more than wall-mounted units.

  • powerful
  • serve multiple component
  • quick and easy installation
  • takes up a lot of space
  • weighs a lot

What is a combi boiler and what are its advantages and disadvantages?

The combi boiler does not have a water storage tank and therefore saves a lot of space. It is also usually mounted on the wall. Because there is no storage tank, the water is always freshly heated. It is particularly suitable for decentralised supply in apartment buildings. Because the boiler heats the water directly, delays can occur from time to time.

  • Space-saving
  • freshly heated water
  • reserve of hot water always available
  • Delay in the process
  • low tapping capacity

What is a compact appliance with a cylinder and what are its advantages and disadvantages?

Storage tanks take up too much space and are integrated into the gas boiler. With a compact appliance you can still save space. The hot water preparation is included here in a compact device. The compact unit is similar to the classic instantaneous water heater.

The unit switches to domestic hot water heating as soon as hot water is required by a component. This type of heating source is optimally suited for use in apartment buildings and small houses.

  • very space-saving
  • hot water directly ready
  • not very suitable in large houses

Although the gas drive is favourable in comparison, there can also be different operating costs under liquid and natural gas.

Buying criteria: You can use these factors to compare and evaluate gas boilers

A gas boiler is not a short-term decision that you make during a break. The decision-making phase is an important process and requires your own prior knowledge plus that of the expert. Not every consumer has certain criteria when buying a gas boiler. It can be different when buying a piece of clothing, because we know our taste and therefore look for something we like.

With a gas boiler, most people do not know exactly what they are looking for, but rely on a third person to make this decision for them, or to make it easier. Now we would like to present and explain some relevant purchase criteria to you, which should make the decision about the purchase easier. It is still your responsibility to seek local advice from a professional on the subject. We present the following criteria:


The gas boiler should fit your home so that it can work efficiently. If the reference values do not match the building area, the energy cannot fulfil its purpose optimally and may be lost.

In order to heat effectively, your gas boiler must be matched to your radiators, among other things. (Image source: / Author: Bernard Hermant)

Houses built before 1970 need a much higher mileage to heat than new buildings. They usually need a heating system with a capacity of 150 – 170W/sqm, which means about 0.15kW/sqm. A conventional boiler usually has a mileage of 20kW or more. New buildings built after 2000 only require an output of 15 – 50W/sqm. If the house has already been renovated, consumers can also switch to a small boiler, as the heat output can be reduced and heat losses are kept to a minimum.

Fuel type

As the name suggests, the gas boiler is powered by gas. We get about 40% of the natural gas in Germany from Russia. We get this from Schalke’s sponsor Gazprom at favourable conditions. The Germans are gradually trying to switch to other types of heating in order to no longer be dependent on Russia. Wall-hung units are usually fuelled by gas and only in the rarest cases by heating oil. But floor-standing therms are operated either by oil, gas or wood/pellet.

Each type has its advantages and disadvantages. Gas is very cheap compared to the other fuel types, but there are methods that are more modern and innovative, such as condensing technology. Consult a specialist dealer to find out which fuel type suits your house best.


The frequency of maintenance of a gas boiler is not prescribed very precisely, but you still need to have it done. It is recommended that you have your gas boiler serviced once a year. However, maintenance does not reduce the efficiency of the appliance and prolongs its life. Of course, a specialist must be called in for maintenance. Maintenance can cost around €100 – €200, but you will be doing your boiler a big favour every year, and it will pay off.

Hot water preparation

Hot water preparation can be done differently depending on whether it is centralised or decentralised. Decentralised means that hot water preparation and space heating are separate. In the case of gas heating, hot water is heated directly at the pump, as can be seen in rented flats. With a central design, all bathtubs and taps are supplied by the storage tank integrated in the gas boiler. In some models, the boiler can also work with an external water storage tank.

Installation costs

Installation costs vary depending on the structural condition of the building. If the house needs a new gas pipe, this is added to the installation costs. In a new building, the costs for the gas pipe are higher than in an existing building. Specialist dealers will offer you different prices for installation, without being far apart.

You can assume that the installation will cost around 1200 – 2000€. The cost of a floor standing gas boiler is very low and so is its cost. The cost of wall mounted units may well cost a little more.

Operating costs

Operating costs can be differentiated between liquid gas and natural gas. Liquid gas costs 0.10€ per kWh and natural gas 0.05€ per kWh. A single-family home averages about 2000 kWh per month, which is about 200€ less than LPG.

The running costs can be the most important aspect. After paying for the appliance, you will always be faced with ongoing running costs.

A single-family house with natural gas, on the other hand, comes to 120€ per month, which is far below LPG. Of course, there are also maintenance costs.

Facts worth knowing about the topic of gas boilers

When does the gas boiler need to be topped up?

When the pressure of the water is no longer sufficient, it must be topped up. Pressure below 1 bar is critical and is a signal to top up the water. Before you refill it yourself for the first time, you should have it shown to you by a professional or read the manufacturer’s instructions.

As a rule, water is topped up 1 – 2 times a year in a gas boiler.

Image source: Yemelyanov/