In Europe, especially in existing buildings, CO₂ emissions are caused by gas and oil heating for domestic hot water and space-heating demand. Renovating buildings with efficient heat pump (HP) systems is essential to meet European climate goals. HP offers a promising alternative to fossil-fuel-based heating systems, but choosing a suitable heat source is challenging. House owners face challenges when switching to heat pump systems because of many uncertainties, such as cost, efficiency, and system assessment. To ease these decisions, a web-based open-source “Decision-Support-Tool” has been developed for technical, economic, and ecological assessment of various heat pump systems for single and multi-family houses. The tool’s technical results are based on detailed simulations using TRNSYS software and validated components such as different heat pumps (brine-water and air-water), photovoltaic-thermal (PVT) collectors, PV, and geothermal heat exchangers. A special focus is put on photovoltaic-thermal heat pump systems, which combine solar-thermal and photovoltaic modules, as a solution for buildings, which have received increasing attention in recent years. The tool provides different tabs for various system analyses, such as detailed techno-economic results and comparisons with other systems. The study presented in the paper consists of a detailed economic assessment of various heat pump systems. Here, the levelized cost of energy (LCOE), which includes all the investment and operating costs for heat and electricity over 20 years, is the lowest for the PVT + brine-water heat pump and PV + air-source heat pump variants at 20.3 ct/kWh.