## 1 Introduction  
Poland's energy policy is based on two strategic documents, namely The Strategy for Responsible Development Until 2020--with Prospects Until 2030, adopted in 2017, and Poland's Energy Policy, which is currently being updated (PEP2040) [1]. The main goal of energy policy is the energy security while ensuring the competitiveness of the economy, energy efficiency, and reducing the impact of the energy sector on the environment, as well as the optimal use of our own energy resources [2; 3; 4]. A number of activities are underway to ensure the stability and continuity of electricity production. One example may be the introduction of the capacity market, which will guarantee financing of maintaining additional capacity in times of an increased demand and peak periods (winter-summer) as well as the protection of unstable energy sources (RES). This mechanism will contribute to the stability of the entire energy system. Additionally, measures are being taken to support the development of high-efficiency cogeneration and renewable energy sources, as well as the implementation of nuclear energy after 2033. In Poland, the basic sources of energy production are thermal power plants, in which energy is obtained by burning coal - most often hard coal or lignite (which constitute 69.58% of the installed capacity of the entire system). The southern part of the country is the largest concentration of these power plants. In larger cities, there are CHP plants fired mostly with coal, but also with natural gas. The production of energy from renewable sources (RES) is also developing especially from wind, water, biomass, and sun. Most of the existing hard coal-fired power plants are obsolete and low-efficiency units. The age structure of boilers and turbine sets operated in power plants is very variable [5; 6]. New generation units--operating for less than 10 years--constitute only 10% of the capacity structure. In total, 57% of generating units are over 30 years old, of which as much as 9% are over 40 years old [6; 7]. Climate and environmental regulations are becoming increasingly stringent for the Polish energy sector, e.g., the introduction of the Best Available Technology (BAT) standard or COM (2018) 773 - a Clean Planet for all - a European strategic long-term vision for a prosperous, modern, competitive, and climate neutral economy. As a result of many years of neglect, the coming years will be a time of huge challenges for the Polish energy sector, especially taking into account difficulties in long-term forecasting of demand for electricity [6]. An accurate electricity consumption forecasting model enables users to constantly adjust consuming behaviors when the market changes [8; 9]. It allows a continuous power supply to consumers [10]. Additionally, for sustainability of the power industrial business, an accurate electricity consumption forecasting model can be used to adjust the production and consumption patterns of electricity. It can also support decisions of energy management policy, such as load unit commitment, the operational security of electrical plants and power systems, economic load dispatching, and energy marketing [11; 12]. In forecasting electricity consumption, there is a problem of the lack of stationarity, which is the result of changes in the assumed strategy. As a result, the statistical models of time series used for long-term forecasts do not generate statistically significant forecasts. Additionally, small sets of input data do not allow for the construction of reliable models. Thus, there is a need for a model that produces reliable long-term predictions for nonstationary waveforms with a small set of input data. The article proposes the use of deep learning techniques to forecast electricity demand, specifically Long Short-Term Memory (LSTM) artificial neural networks. These models are able to deal with the nonlinear nature of the phenomenon and with a small set of input data.