This paper presents an analysis of the energy potential of grape stalk biomass from PIWI varieties, namely ‘Seyval Blanc’, ‘Muscaris’, ‘Hibernal’, and ‘Regent’, during the combustion process. Biometric, technical, and elemental analyses of the grape stalk biomass were conducted. We evaluated the mass, length, and width of the stalks and their contribution to the total cluster mass. The higher and lower heating values, moisture content, volatile compounds, ash, fixed carbon content, and elemental composition were analysed. Emissions of carbon monoxide, nitrogen oxides, carbon dioxide, sulphur, and particulates were also measured. A significant influence of the cultivar on the assessed biometric and technical parameters was found. ‘Muscaris’ exhibited the highest calorific value (HHV 16.44 MJ·kg−1) and the lowest ash content (9.99%). The highest carbon content (45.51%) was recorded for ‘Seyval Blanc’, and the highest hydrogen content (6.74%) for ‘Muscaris’. Nitrogen oxide emissions were the lowest for ‘Seyval Blanc’, making it more environmentally friendly. The biomass of grape stalks from PIWI varieties, particularly ‘Muscaris’ and ‘Seyval Blanc’, shows high energy potential and can be effectively utilised as a renewable energy source. Our results could be summarised as ‘sustainable energy production and reduced greenhouse gas emissions from grape stalks’.