Widespread modernisation of social housing is essential if the country is to avoid exacerbating energy poverty in its cities. In Poland, the inhabitants of social housing estates are people with low and insecure incomes; their homes are often in poor condition and are usually heated with either coal stoves or electric heaters. Municipal governments own social housing flats. Therefore it is up to them to improve the living conditions of residents in a sustainable manner. However, municipal governments have limited resources for modernisation, and the current energy crisis will only tighten their pockets further. We propose that three critical social criteria are considered when assessing and implementing social housing energy efficiency investments: 1) Efficiency, 2) Solidarity, and 3) Reduction of External Costs. Adhering to these criteria will allow municipalities to retrofit social housing more equitably – meaning that investments will serve those most in need while limiting their environmental impact.