Breakdowns lasting for months, neighborhoods without hot water and increasingly difficult repairs – the problems of „Toplofikatsia Sofia“ are now raising questions not only about the condition of the network, but also about the future of district heating in the city.
The cause is not a single damaged pipe. Years of insufficient investment and slow infrastructure replacement have led to a buildup of serious problems, whereby fixing one breakdown often triggers another. How serious is the situation, and is there a way for Sofia to preserve its district heating system while making it more reliable, affordable and less polluting?
Fig. 1: Map of some of the current breakdowns in the „Toplofikatsia Sofia“ network. Source: The company’s information bulletin dated 11.11.2026.
Repairs that can no longer keep up with the breakdowns
Sofia’s district heating system operates approximately 1,000 km of heating pipelines made of steel pipes. The modern pre-insulated pipes installed by the company when replacing sections of the network have a service life of 30 years when stored, installed and used in accordance with best practices. This means that at least 33 km of the heating network must be replaced every year in order to maintain it in the same technical condition.
Fig. 2: Replaced pipelines from the „Toplofikatsia Sofia“ network for the period 2021–2025, in linear kilometers.
The requirement to replace 33 km of pipelines has systematically not been met during the period under review (as shown in Fig. 2). Between 2010 and 2020, just 107 km were replaced, amounting to less than 10 km per year. This means that the problematic sections increase with every passing year, and their accumulation naturally leads to a cascade of breakdowns.
The breakdown repair work itself requires the fluid to be completely drained from the pipelines, followed by refilling them under high pressure for hydraulic leak testing. During these processes, already corroded and heavily worn pipes are subjected to additional stress, which often causes new ruptures. Thus, in a degraded district heating network, a vicious cycle is set in motion in which repairing one breakdown creates conditions for further damage.
Why are breakdowns no longer simply breakdowns?
The fact that some breakdowns have not been repaired for nearly three months shows that the problem can no longer be reduced to the routine replacement of a particular section. This precedent is a clear signal of the risk of far more serious disruptions to the heating supply.
The company’s network is divided into four heating districts. All breakdowns continuing for months are concentrated in just one of them – the „Sofia East“ heating district, which is the largest and covers almost half of the entire network. It is served by just one plant – the „Sofia East“ Combined Heat and Power Plant. It supplies hot water from its location at the edge of the „Druzhba“ residential district all the way to the „Vitosha“ and „Lozenets“ neighborhoods and parts of the city center. The network’s connection with the „Sofia“ and „Zemlyane“ heating districts is limited and does not allow for the full redistribution of loads.
These details are important because the distance the water has to travel from the „Sofia East“ CHP plant to its end points exceeds 10 km, while the elevation difference is more than 60 meters. To overcome hydraulic resistance and compensate for thermal losses, the hot water must leave the plant at greatly increased temperature and pressure parameters. If, for some reason, these values cannot be reached, some neighborhoods will not receive a service of normal quality.
In recent years, the „Sofia East“ heating district has operated with exceptionally high volumes of make-up hot water – more than 900 tons per hour. This is water that leaks through defects in the network and must be constantly replenished. Such a flow rate exceeds safe operating limits several times over and exhausts the capacity for chemical treatment of the water before it enters the network. If complete treatment is bypassed, the water becomes aggressive and causes accelerated, widespread corrosion.
As the heating season approaches and leaks from the cascading breakdowns increase, the company is forced to isolate entire sections in order to stop the losses in them and keep the make-up water within critical limits. At the same time, insufficient pressure is appearing in some of the higher parts of the city. The pressure cannot be increased at the plant because this would intensify leakage through ruptures in the network. Support from neighboring heating districts at maximum flow is also proving insufficient to patch up the situation.
Could entire neighborhoods be left without district heating?
It is highly likely that some neighborhoods will have no hot water or heating from „Toplofikatsia Sofia“ at all this season and will have to seek individual solutions. This will most likely prompt a large share of affected consumers to look for alternative heating.
The municipal company, which is already in an unenviable financial position, will lose a substantial share of its revenue without this reducing its costs. Even if heating use is effectively discontinued, many consumers will not go through the official procedure for opting out. The company will remain legally obliged to restore supply and, otherwise, will be subject to penalties and sanctions from the Ministry of Energy.
On this basis, it is reasonable to assume that „Toplofikatsia Sofia“ will be forced to technically „withdraw“ from certain areas in order to preserve the functionality of the rest of the network. It is unclear how far this process will go, but the reduction in supply could affect everything beyond the recently replaced sections and the main pipelines leading to them in the “Sofia East” heating district.
Since this will reduce the consumed flow to a much greater extent than the physical distances would suggest (due to the dispersion of subscribers), heat losses across the network could rise to more than 20–25% during the heating season and over 60–65% outside it. Such a scenario, combined with the fact that the company’s liabilities – approximately EUR 1.4 billion – are approaching the value of its assets and that it may soon be technically insolvent, strongly suggests that this could be the last heating season for a large share of subscribers.
Cheaper and cleaner heating – but for whom?
A frequently used argument for saving „Toplofikatsia Sofia“ is that it provides energy at a „socially affordable price“. In recent years, however, this has not entirely corresponded to reality.
At the time of writing, consumers pay EUR 73.30/MWh for supplied heat, plus a metering fee and technical losses (which account for a significant part of the bill in old panel buildings).
For comparison – when switching to gas boilers and water heaters, the price is EUR 83.53/MWh of thermal energy (along with all the drawbacks of using fossil gas). With a heat pump with a seasonal coefficient of performance (SCOP) of 3.8 and current electricity prices, the cost falls to EUR 26.99/MWh of thermal energy.
Another common argument is that the electricity distribution network would not withstand the load if there were a mass switch away from district heating. This claim, however, is not based on specific measurements and data, but rather on personal impressions. Ember-Energy data shows that Bulgaria ranks second in Europe (after Norway) in the degree of household electrification.
Fig. 3: Share of electricity in total household energy consumption in Bulgaria/ Source: Ember-Energy – Europe Electrification Data Explorer (Data for Bulgaria)
The bulk of household energy in Bulgaria is already electrified (reaching 21.5 TWh in 2025), while total household consumption has been steadily declining every year since 2021. Even if electrification were to increase sharply due to the discontinuation of district heating, no critical change in the overall load is expected.
The NSI census shows that 78% of urban households already have air conditioners. Due to the high efficiency of heat pump systems, each unit of thermal energy from district heating is replaced by just 0.22–0.30 units of electricity. This means that the electrification process is unlikely to be problematic for most residents of the capital.
The main challenge will be for the most vulnerable households, which cannot afford the initial investment in an air conditioner or heat pump. This is precisely where the state should intervene with targeted support in the event of a prolonged interruption of the service.
In terms of climate and air quality, shutting down „Toplofikatsia Sofia“ would have a rather positive short-term effect. The company uses natural gas for 100% of its production. The emission factor for burning natural gas is 0.202 tCO₂eq/MWh [6]. With transmission losses of 24.7% and equipment efficiency of approximately 90% [1], only two-thirds of the energy generated reaches end users. Thus, the effective emission factor of district heating becomes approximately 0.300 tCO₂eq/MWhth.
For comparison, the carbon footprint of heating with an air conditioner is calculated on the basis of the projected emission factor of Bulgaria’s electricity mix for 2026 (0.278 tCO₂eq/MWh according to the Ministry of Environment and Water [7]), divided by the seasonal efficiency SCOP = 3.8. The figure is just 0.073 tCO₂eq/MWhth – i.e. a carbon footprint nearly four times lower. The comparison is based on the stated assumptions regarding efficiency and the electricity mix.
The impact of district heating on urban air quality is also significant. The Executive Environment Agency refused the company’s derogation request concerning nitrogen oxide emissions [8] – a major precursor of ultrafine particulate matter. The refusal was upheld at second instance, but the plants continue to operate in violation, exceeding the limits twofold. With electrification, this problem is absent at the local level, since the main electricity generation takes place outside cities, while the growing share of renewables is continuously reducing the average emissions of the mix.
After all this, the logical question arises: should Sofia residents give up district heating?
Should Sofia give up district heating?
The short answer is no. Despite the short-term benefits for air quality and the climate, the heat transmission network is a valuable resource and tool in the long-term fight against greenhouse gas emissions.
Although electrification provides flexible individual solutions, there are exceptionally efficient and clean technologies that can be applied only on a large scale. These include deep geothermal wells (extracting water at temperatures above 60–80 °C), the utilization of waste heat, industrial heat pumps and thermal energy storage systems.
These facilities can be integrated most easily into an operating network with existing building installations, allowing the implementation of rapid and large-scale municipal policies. The maximum potential of these technologies to save money and emissions exceeds that of individual electrification, but their deployment requires time and planning.
How can we save the network without saving the old model?
Without fundamental restructuring, „Toplofikatsia Sofia“ cannot be a profitable, efficient or environmentally friendly company. Even if its debts were written off, it would begin accumulating new ones from the very first day.
Concessioning the company and handing it over to a private operator is not a panacea either. There are examples in Bulgaria of private district heating companies managed by experienced international firms, but they have not seen large-scale investment or network expansion. The reason lies in the regulatory framework, which does not encourage modern environmental solutions. Investors avoid expansion into new neighborhoods because of the high risk of failing to recover their investment. In private hands, „Toplofikatsia Sofia“ would most likely achieve only operational optimization of its existing gas-fired capacity, the fuel for which will become increasingly expensive.
A sustainable solution requires coordinated action between the municipality and the state in the form of a new master plan (Road Map) from the Municipality, focusing on the decarbonization, decentralization and diversification (3D) of heating and cooling. The network must be divided into small, low-temperature sections supplied by local sources – waste heat, solar collectors and industrial heat pumps. This would eliminate the risk of vulnerability affecting the entire system (as is the case in the „Sofia East“ heating district), while such modules could be built within 1–2 years.
There is also a need for legislative reform through replacing the current fossil fuel subsidy model with mechanisms supporting modernization, in line with European requirements for efficient district heating systems.
The executive branch must initiate exploratory drilling for deep geothermal energy and attract experienced international companies to develop the sector.
Even if the company goes into liquidation, this would not mean the end of centralized heating in Sofia. The municipality must preserve the key assets for the future plan, renegotiate terms with creditors and communicate the steps transparently to citizens. It is important for municipal councilors to understand that the interests of citizens and those of the company diverge, but the most valuable capital to preserve is consumer trust and their connection to the network, not the company’s outdated equipment.