Building and buying

Oil heating: functioning, installation and costs

Thomas Bott

As shown by the figures last collected by the Federal Statistical Office in 2017, oil heating is still the most widespread method of heat generation in Switzerland. But the heating systems installed in households are not always up to date with the latest technological developments. So it can be worthwhile for the environment – and your wallet – to think about replacing your heating system. Even people who are planning a new house or an energy conversion may consider oil as a source of energy. Here you can find out how oil heating works, the advantages and disadvantages, how much it costs and whether it pays off.

A woman wrapped in a blanket with a cup in her hand sits by the window and looks out.
© Getty Images

In this article

Oil heating: components and functioning

The basic structure of an oil heating system is quite straightforward. Only a few important components are needed to generate heat with oil as a raw material.

  • Oil tank: the tank contains the fuel oil required for combustion, which it passes on to the burner. The oil tank has a double-walled construction and is very robust. It is available in different shapes and sizes. To heat an average single-family house, the tank should have a capacity of at least 3,000 liters of oil.
  • Oil boiler with burner: heat is generated by the combustion of the raw material at the heart of the heating system. A heat exchanger transfers the heat to the heating water. Modern systems rely on condensing boiler technology. More on this later.
  • Heat regulation: for the oil heating system to supply the required heat, a control system is needed. This regulates the amount of fuel oil entering the burner and the distribution of heat in the house.
  • Circulation pump: this component pumps the heated water through the pipes to the individual radiators and returns colder liquid back to the system. It maintains the water circuit to conserve the desired temperature.
  • Exhaust system: the combustion of oil produces exhaust gases. The exhaust system filters these outside into the fresh air.
A workman carries out work on a chimney. A valley and mountains are visible in the background.

If you switch to a condensing oil heating system, structural changes to the chimney are necessary. You should bear this in mind during the planning stage.

Condensing oil heating: more efficiency through modern technology

With old boilers, a lot of heat is lost via the exhaust air. This makes classic oil heating systems very inefficient. Only about 70 percent of the energy can be used. It is better to replace an old system with a modern condensing boiler, which will operate much more efficiently, and use around 95 percent of the energy available. The condensing oil heating system directs the hot exhaust gas past a heat exchanger, which absorbs the residual heat and returns it to the heating circuit. The gases coming out of the chimney are therefore significantly cooler than those from older oil heating systems.

However, this intense cooling also produces condensation water, which the system has to drain off. A water drain is therefore necessary. If you already have an oil heating system, changes to the chimney are also required because the exhaust pipes need to be as insensitive to moisture and as resistant to corrosion as possible. This makes materials like plastic the most suitable.

A radiator below a window in a room in the attic of a house.

When a heating system is modernized, the existing radiators can remain in the rooms. They will continue to function with the new technology.

Installation: what you need for an oil heating system

If you replace your old boiler with a new one that uses condensing technology, it usually won’t take up any extra space. Even the old oil tank can remain in place, as long as it is still intact. However, you can’t forget the above-mentioned changes to the chimney because more moisture (condensation) is produced from condensing boiler systems than from other systems. If, on the other hand, you decide to install a whole new heating system, a little more planning is necessary. The tank takes up a lot of space, especially if you choose a model with a high capacity.

To ensure that delivery is not a problem, easy access to the tank or a filler spout on the house is also needed. The boiler itself should ideally be installed on a level surface. It is therefore usually fitted in a large basement room. Another requirement is a chimney that is suitable for the exhaust gases from the oil heating system. A heating engineer will help you to plan the new heating system in line with your requirements and the space available.

View of a modern condensing boiler connected via pipes to an oil heating system.

The boiler is the heart of the oil heating system. A tank is also needed to store the fuel.

Costs: purchasing and operating the heating system

If you buy a new oil heating system, costs will be incurred for the boiler, the tank, the installation and any structural changes that have to be made to the building. Prices range from around 25,000 to 35,000 francs. This puts oil heating on about the same level as other heating technologies such as heat pump or pellet heating systems. If, on the other hand, you only buy a new condensing boiler, you can expect to pay around 10,000 francs.

The running costs for oil heating are subject to (sometimes considerable) fluctuations. This is because they depend on the current oil price. With a bit of luck, you can obtain heating oil at a very favorable price. That’s when it may be worth buying a little extra. Some people with oil heating systems opt for a larger tank precisely so that they can purchase and store larger quantities of fuel more economically. In mid-2020 the price of a liter of heating oil was around 66 centimes.

Ecology: how to make oil heating slightly better for the environment

The production, transport and combustion of oil produces substances that are harmful to the environment. In addition, oil is a finite raw material – and therefore not sustainable in the long term. The environmental impact of an oil heating system is therefore quite negative. To improve this, you should make sure you have a state-of-the-art boiler. Ideally, you should also use fuel oil with the highest possible bio-oil content.

It is even better to combine oil heating with renewable energies. It works well with a solar thermal system, for instance. This is used to produce heat whenever enough solar energy is available. The oil heating system tops up the rest to cover demand. This has a very positive impact on the environment. Alternatively, it’s possible to couple oil heating with a geothermal heating system. Although a second system leads to extra costs, savings are also possible, for example with regard to the fuel in the oil tank.

Conclusion: modernization is worthwhile, but a new acquisition may not be

The purchase of a new oil heating system is associated with high costs, especially as it should ideally involve incorporating a more environmentally friendly system using renewable energies. You should therefore seriously consider choosing another heating system right away instead.

If you want to modernize your old oil heating system, it pays off simply because of the much higher efficiency of modern condensing technology. But here too, caution is called for because the price of heating oil could rise sharply in the future. After all, most countries want to make fossil fuels increasingly unattractive.

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