The federal government is calling on citizens to save on gas. In an interview with ntv.de, Jürgen Leppig, CEO of the Energy Advisory Association GIH, explains how one's own heating can be optimized, in which cases it is worth switching to a different technology and what needs to be considered with heat pumps. He thinks little of the current rush to fan heaters and wood-burning stoves.
ntv.de: We are supposed to save gas, and its price is rising massively - for whom is it even worth replacing the gas heating in the basement?
Jürgen Leppig: When she's too old, around ten years old. This can save up to 20 percent energy. An exchange is particularly worthwhile for calorific value heating systems, because these do not use the condensing effect. Make sure that the factory settings of the heating are adapted to your building. Unfortunately, that happens far too little. Incidentally, the federal government is considering introducing an exchange bonus for gas heaters as well.
Which technology can currently best be used to replace gas?
If there is a local or district heating network, you should use it. If you don't have this option, you should consider installing a heat pump. This is not always possible for various reasons such as noise, space or the building's heat requirements. However, a "species-appropriate" heat pump will be the right solution in most cases. A hybrid solution should also be examined, i.e. additional heating to the heat pump to generate high temperatures in order to generate heat economically at very cold temperatures. If all this is not possible, a pellet heating system would also be a solution, for which you need storage space. There is no one best solution, it always depends on the individual circumstances.
A hybrid solution sounds expensive to buy.
In addition to the average device costs of 10,000 to 12,000 euros for an air heat pump for a single-family home, this adds another 3,000 euros. At the moment, however, the offers are difficult to quantify. In addition to very long delivery times for material, we have far too few craftsmen. Today you wait twelve months for a heat pump.
Does it make any sense at all to replace my gas heating at the moment?
Yes, you should definitely think about what would be the best concept for your house together with an energy consultant or heating engineer. Because it is already difficult to find these experts, it is important to do this in good time - before the heating system breaks down in the worst case. In addition, the heat transfer system should be adapted to the new heating system. This means that a significant amount of electricity can be saved again with a heat pump. The state also promotes this very attractively.
What solution do you recommend for apartment buildings?
That is the most exciting question, for which there are still no good off-the-shelf solutions. If you only have a small gas boiler on the wall, you can't always replace it. In some apartments, an exhaust air heat pump can be used, which uses a heat pump to return the heat from the air that is otherwise let out of the window back into the apartment. Another solution would be to switch to central heating for the whole house, if that is possible. If there is no space in the basement, there may be space in the courtyard or in outbuildings.
If I can't or shouldn't replace my gas heater, how can I optimize it?
First of all, you should clarify whether you have a high-efficiency pump in your heating system. There are still many thermal heating circulation pumps that consume a lot of electricity: up to 90 instead of 8 to 10 watts. A high-efficiency pump saves more in the warranty period than it costs. This can save you up to 200 euros a year.
The next thing to check is that all plumbing is properly insulated - most boiler rooms are so warm you'll need to hang your laundry out to dry. You can even insulate yourself, the material is available in hardware stores or specialist shops and is not very expensive.
What else helps to reduce gas consumption?
You should check whether a hydraulic balance has been made. This ensures that only as much heat is brought into the room as is required to warm it up. This saves energy. Depending on whether the valves on the radiators have to be changed, it costs around 1000 euros. The costs are usually amortized after five or six years. With a high-efficiency pump and hydraulic balancing, you save several hundred euros per year in electricity and heating costs.
When the hydraulic adjustment is complete, the so-called advance curve of the heating can be adjusted to the meanwhile warmer winter temperatures. This is done by a heating engineer as part of the maintenance. If you read the operating instructions, you can also do it yourself.
Economics Minister Robert Habeck has also called for maintenance - what will it cost me?
In fact, maintenance by a specialist is required by law every year, but this is not checked. You should be interested in this, however, because you can use it to reduce your operating costs. Maintenance should be done in addition to optimization. Because only if the system is fault-free can it be heated cost-effectively and in an environmentally friendly manner. However, it is difficult for me to quantify the maintenance costs because the hourly labor costs vary between 50 and 100 euros depending on the region.
What is your advice to tenants whose apartment or house is heated with gas?
Talking to the landlord to find a mutual solution. Tenants can also have energy advice and renovation measures subsidized by the state if the landlord agrees.
What do you recommend to landlords?
To think about how to solve the dilemma we are in at the moment. In order to maintain the value of the property, I recommend the same measures as for inhabited property.
Do you have another insider tip?
In my opinion, ventilation heat losses are not taken into account enough when saving energy. A ventilation system with heat recovery can save 80 percent of ventilation heat loss. The ventilation is an optimal addition to the heat pump. While the heat pump degrades in cold temperatures, ventilation heat recovery increases when it gets really cold outside.
What about heat pumps that work with geothermal energy?
Because of the drilling, it costs at least twice as much as for air heating, and drilling is also not possible everywhere. Heat pumps whose heat source are so-called PVT collectors, which generate heat and electricity at the same time, are not yet so well known. These are photovoltaic modules that generate electricity - an additional heat exchanger extracts heat from the circulating air. As a result, the efficiency is just as high as with geothermal energy. The state also supports this technology.
Is that your current recommendation for home builders?
If it is somehow financially possible, the building shell should be as good as possible in a new building so that the heating is as small as possible. This makes you independent of variable costs. A really well-insulated building - which is also possible with wood and stone - means high investments, but low operating costs.
Air source heat pumps are now the most common heating technology in new buildings. This is usually the best solution, plus photovoltaics on the roof and ventilation with heat recovery - although of course it always depends on the individual case.
For this I recommend surface heating so that the flow temperature is as low as possible. What heating engineers often don't have on their radar: Don't forget the ceiling! This is the best surface for heating and cooling: little mass in the system, cooling with physics. While the floor screed has to be heated first, the ceiling warms up very quickly and requires a low flow temperature. Every degree less saves around 2.5 percent electricity.
How much does an individual energy consultation cost?
The state subsidizes 80 percent of the costs for the so-called individual renovation schedule. This allows you to get your building up to efficiency house level. In the case of a one- or two-family house, you have to pay at least a personal contribution of 325 euros. The prices are also higher depending on the region and demand.
What do you think of electric heaters?
If a building needs extremely little heat, for example a passive house, you can consider whether you can do with infrared electric heating. But always remember: 1 kWh of heat equals 1 kWh of electricity today equals almost 40 cents. With a heat pump, you only pay about a third of that.
A lot of people are buying fan heaters these days. We're talking about heating costs for a medium-sized German building of over 500 euros a month - who wants to pay that? Electricity is an emergency solution for an extreme crisis situation. If the gas-fired power plants that generate electricity also fail, the power grid would not even allow heating with electricity.
Wood-burning stoves are also fashionable, but there is currently a shortage of wood and its price has risen sharply - what is your advice to owners?
The Federal Environment Agency has already referred to the pollutant emissions - the best piece of wood is that which is not burned. If there is no more gas, it is of course a possibility to keep your building reasonably warm. Then please only burn dry, untreated wood.
And what do you recommend to consumers who heat with oil?
Like gas, oil is a fossil fuel that should no longer be used for climate protection reasons. The war in Ukraine also taught us to greatly reduce our dependency on foreign countries. I fear, however, that efforts will drop sharply as soon as gas and oil become cheaper again. Since the installation of oil heaters will be banned in Germany from 2026, some consumers are now quick to install one. Instead, they should see whether they can switch to renewables as early as possible. This is not always easy, especially in rural areas. But there you can check, for example, whether there is a farmer with a biogas plant nearby, which produces heat and gas, and build a local heating network. We must finally consider all possibilities.
Christina Lohner spoke to Jürgen Leppig