About 55% of over 14 million Polish households live in multi-family buildings. Cooperative or housing association buildings have a large share in this group. The heat is supplied from the district heating network or from local sources. With respect to facilities fed from gas boiler rooms, the signing and execution of fuel supply contracts is required. From October 1, 2017, the obligation to submit tariffs for gas trading set for all final customers (except for individual gas consumers in households) for approval to the President of the Energy Regulatory Office was lifted. Decisions regarding the choice of the supplier and the content of the concluded contract are made by the authorized bodies of the cooperative or housing association. The consequences of such decisions are borne by the owners and users of residential premises. Ensuring the continuity of a contract for the supply of gaseous fuel essentially comes down to establishing prices and rates in force for a given period. The right decision on the moment of signing the contract or the amendment, termination of the existing contract and signing a new one, or negotiation efficiency will result in financial profits for all users. The costs of heating and domestic hot water preparation are a significant component of the overall cost of the maintenance of flats in Poland. Therefore, it is even more important that the prices and rates agreed upon with the gas supplier are as favorable as possible to users. The high costs of heat are not only expenses for apartment owners. The attractiveness of flat on the rental market is also decreasing. The business activity carried out in facilities located in such buildings is also less competitive.

The authors of the article analyzed gas prices on the Polish market over the last 3 years and presented the results of simulations of the effects of specific prices and rates set in the contract for the supply of fuel at the cost of heating from the point of view of a single apartment. As these are not large amounts per year, they do not motivate to optimize the terms of the gas purchase contract in this respect. The dynamics of changes in gas prices in Poland, although slightly different from world trends, is high. This makes it difficult for those responsible to make the decisions, and for residential users, it often means spending differences in subsequent years. One of the consequences of setting prices and rates significantly higher than obtainable may also be the reluctance of local communities to take measures to increase the energy efficiency of the heat supply system. From the point of view of heating costs, such decisions may distort the economic effect of thermo-modernization.

Describing the gas boiler fuel consumption as a time series gives the opportunity to use tools appropriate for the processing of such data to analyze this phenomenon. One of them are ARIMA models. The article proposes this type of model to be used for predicting monthly gas consumption in a boiler room working for heating and hot water preparation. The boiler supplies heat to a group of residential buildings. Based on the collected data, three specific models were selected for which the forecast accuracy was assessed. Calculations and analyses were carried out in the R environment using “forecast” and “ggplot2” packages. A good quality of the obtained forecasts has been demonstrated, confirming the usefulness of the proposed analytical tools. The article summary also indicates for what purposes the forecasts obtained in this way can be used. They can be useful for diagnosing the correct operation of a heat source. Registering fuel consumption at a level significantly deviating from the forecast should be a signal to immediately diagnose the boiler room and the heat supply system and to explain the reason for this difference. In this way, it is possible to detect irregularities in the operation of the heat supply system before they are detected by traditional methods. The gas consumption forecast is also useful for optimizing the financial management of the property manager responsible for the operation of the boiler room. On this basis, operating fees or financial operations with the use of periodic surplus capital may be planned.

W bieżącym stuleciu stosowane są dwa najczęściej spotykane sposoby zaopatrzenia w ciepło kompleksów budynków wielolokalowych. Pierwszym z nich jest zasilanie w ciepło systemowe z sieci ciepłowniczej, a drugim – budowa i eksploatacja lokalnych kotłowni gazowych. Wykorzystanie innych nośników ciepła występuje tylko wówczas, gdy nie jest możliwe podłączenie źródła ciepła do sieci gazowej lub sieci ciepłowniczej. Budynki wielolokalowe charakteryzują się daleko idącą specyfiką w wielu obszarach swojego funkcjonowania, w tym także w zakresie zużycia ciepła. W przypadku kotłowni gazowych konsumpcja ciepła bezpośrednio przekłada się na pobór paliwa gazowego. W artykule przedstawiono i scharakteryzowano zużycie paliwa gazowego przez lokalną dwufunkcyjną kotłownię na podstawie pomiarów wykonywanych z dużą częstotliwością odczytu. Wiedza na temat procesu poboru gazu, nawet w przypadku jeżeli dotyczy to niewielkich ilości, w skali zużycia krajowego, może być podstawą dla poprawy przebiegu tego procesu. Dotyczyć może to nie tylko aspektu ekonomicznego, ale również technicznego, a także punktu widzenia bezpieczeństwa energetycznego oraz efektywności energetycznej. Z tego względu wszystkie podmioty związane z dostawą i odbiorem paliwa gazowego dla zespołu budynków wielolokalowych powinny być zainteresowane poszerzeniem wiedzy na temat tego procesu.

The article discusses issues related to improving the energy efficiency of heat supply systems. It draws attention to the need to take action not only for large objects and systems, but also for individual buildings and their boiler plants. Heat supply system monitoring allows for the diagnosis of the weakest elements and making decisions leading to the improvement of energy efficiency. In the case of the boiler room where the research was carried out, the results of such monitoring convinced to equip boilers with an additional automatic control system, with an algorithm limiting the number of burner switching cycles and shutdowns. Limiting the number of switching on the burners, as in the case of other combustion and electric devices, has a significant impact on the energy efficiency of the entire system. In addition, it also increases the durability of the devices, and thus reduces costs of servicing and repairs. The simplest control algorithms, often used in controllers installed in the boiler units, do not provide optimization in this respect. The external device used has allowed the number of burners on and off cycles to be limited while maintaining the quality of the heat supply to the heating installation and the heat treatment system.

The material also presents other ways to improve the energy efficiency of the heat supply system in existing multi-family buildings.

The article presents the results of surveys to assess the attractiveness of centralized heat supply systems in comparison with other heat sources. The heat source is an important element of the heat supply system which determines heating costs, comfort and environmental impact. The decision on the choice of the type of heat supply system is usually made by the investor or designer. Sometimes the equipment supplier or contractor has a part in this decision. The choice can be influenced by many different factors, also resulting from the specific location of the building. This is only partly determined by local law in the form of a local spatial development plan. the technical conditions (i.e. availability of heating or gas network), economic and financial, as well as much more subjective factors, such as the designer’s or contractor’s preference are also important. Aversion to district heating is growing, even when there are favorable conditions and the possibility of connecting the building to the heating network. Instead, a gas boiler or electrically powered heat pump is selected. This raises the question of whether such decisions are right and how they can be justified. As a research method, surveys were used, which were conducted among people who already have or will have an impact on design and investment decisions in the near future. The obtained results confirmed a large interest in district heating, appreciating their advantages in comparison with other methods of heat generation. The respondents also had the disadvantages that may lead to the use of an alternative methods of heat supplying in mind.

The heat supply systems energy efficiency improvement requires the use of increasingly complex methods. The basic ways to reduce heat consumption is by using better thermal insulation, although they have more and more limited possibilities and need relatively large financial outlays. Good effects can be achieved by the better heat source adaptation to the conditions of a specific facility supplied with heat. However, this requires research that identifies the effectiveness of such solutions as well as the tools used to describe selected elements of the system or its entirety. The article presents the results of tests carried out for a gas boiler room supplying heat to a group of residential buildings. The goal was to build a model that would forecast the day range in which the maximum gas consumption occurs for a given day. Having measurements of gas consumption in subsequent hours of the day, it was decided to build a forecasting model determining the part of the day in which such a maximum would occur. To create the model the random forest procedure was used along with the mlr (Kassambara) package. The model’s hyperparameters were tuned based on historical data. Based on data for another period of boiler room operation, the results of the model’s quality assessment were presented. Close to 44% efficiency was achieved. Tuning the model improved its predictive ability.