District heating (DH) systems can contribute substantially to the decarbonization of the heating sector by enabling the implementation of sustainable heating solutions such as ambient heat (AH) and waste heat (WH). However, these sources are subject to economic risks arising from uncertainties in future energy prices and availability. This paper presents a techno-economic analysis for a decarbonized DH network for a city in Poland, using a simulation model that evaluates levelized cost of heat (LCOH) across a wide range of heat supply portfolios including AH and WH sources. It considers uncertainties related to energy price and WH cessation scenarios as well as sensitivities related to WH prices, heat demand, and biomass availability. Results show that the DH system configuration plays a key role in determining the average cost, due to the relatively large share of CAPEX in the LCOH calculations, underscoring the importance of accurate investment cost assumptions. Further important factors are the development of the heat demand and the availability of biomass. The presence of low-cost industrial WH is beneficial. In general, there is a trade-off: minimizing average cost results in a higher economic risk.