District heating (DH) is a key component of Sweden’s heating infrastructure, more than half of which is currently reliant on biofuels. However, recent energy scenarios from the Swedish energy agency (March 2025) project up to an 80 % reduction in biomass use by 2035, creating an urgent need for alternative heat sources for district heating. Solar thermal collectors and heat pumps combined with short- and long-term storage represent a promising solution, yet their optimal integration and performance remain largely underexplored in the Swedish DH context. This study presents a techno-economic analysis of integrating solar thermal collectors, pit thermal energy storage, and a heat pump in the Härnösand DH network. A multi-stage simulation approach combining simplified (in Python) and detailed (in TRNSYS) models was used to optimize system design. Geological assessment and hydraulic constraints identified a DN400 feed-in pipe as optimal. Results show that a 35 % solar fraction minimizes the levelized cost of heat (LCOH), with an optimized system comprising 102 000 m² of collectors, 325 000 m³ PTES, and a 5 MW HP. The LCOH of the evaluated system is 70 €/MWh at 5% discount rate for 20 years. The study highlights the importance of accounting for practical constraints including feed-in pipe size, geological conditions, PTES location, and integration strategy for achieving cost-effective solar district heating integration in Swedish networks.