The generation stage
Most heat in Polish urban district systems originates at combined heat and power (CHP) plants, known in Polish as elektrociepłownie. These facilities burn natural gas, coal, or biomass to generate electricity in turbines while simultaneously capturing the thermal energy that would otherwise be released as waste heat. The recovered heat is transferred to the primary distribution circuit's water supply.
In cities where a CHP plant is not available or not large enough to cover peak demand, heat-only boiler stations (ciepłownie) supplement output. Boiler stations run primarily during winter peak periods, burning gas or biomass to boost network temperature and flow.
Primary distribution network
From the plant, hot water enters the primary network — a city-wide system of insulated underground pipes, typically pre-insulated polyurethane foam (PUR) pipes encased in a polyethylene outer jacket. These carry water at supply temperatures ranging from approximately 70 °C in summer to 130 °C during the coldest winter days, with corresponding return temperatures roughly 20–40 °C lower.
The temperature differential between supply and return lines determines how efficiently heat is extracted at each substation. A larger differential means more energy delivered per unit of water circulated, reducing pump energy consumption across the network.
Large pumping stations distributed along the network maintain water circulation pressure. The network operates as a closed loop: water circulates continuously from plant to substations and back, with the same treated water reused indefinitely. Makeup water is added only to compensate for minor losses from leaks or maintenance work.
Heat substations
At each building or group of buildings, a heat substation (węzeł cieplny) connects the primary network to the building's internal installation. The most common configuration in modern Polish buildings is an indirect substation using a plate heat exchanger. In this arrangement:
- Primary network water enters the heat exchanger and transfers energy to a separate secondary circuit serving the building.
- The two circuits remain hydraulically isolated — primary network water never mixes with the building's water.
- The secondary circuit supplies both space heating radiators and domestic hot water preparation.
Older installations, particularly in pre-1990s residential blocks, may use direct connection substations where primary water circulates directly into the building's installation, though these configurations are being phased out during network modernisation programmes.
Building-level distribution and metering
Within the building, the substation output feeds a distribution system that serves individual apartments or floors. Heat meters — certified devices measuring both water flow volume and the temperature difference between supply and return — record consumption at the delivery point. In multi-family buildings, apartment-level heat cost allocators may be installed on individual radiators to apportion the building's total metered consumption among tenants.
Polish regulations require that heat meters meet technical standards defined by the Polish Committee for Standardization (PKN) and comply with EU Measuring Instruments Directive 2014/32/EU (MID). Remote meter reading systems are increasingly being deployed to reduce manual meter inspections and improve billing accuracy.
Seasonal operating patterns
Polish district heating networks operate seasonally in terms of space heating, but domestic hot water supply continues year-round. The heating season typically runs from mid-October to late April, though actual start and end dates are determined by outdoor temperature thresholds set in supply agreements. When daily mean outdoor temperatures remain above a defined threshold (often 12 °C or 15 °C) for several consecutive days, the network operator may suspend space heating supply while maintaining domestic hot water circulation.
Network operators in major cities
| City | Primary operator |
|---|---|
| Warsaw | Veolia Energia Warszawa S.A. |
| Kraków | MPEC Kraków S.A. |
| Poznań | Veolia Energia Poznań S.A. |
| Gdańsk | GPEC S.A. (Energa Group) |
| Łódź | Veolia Energia Łódź S.A. |
| Wrocław | FORTUM Power and Heat Polska Sp. z o.o. |
Operator information is sourced from publicly available company registrations and regulatory filings with the Energy Regulatory Office (URE).