The majority of industrial, residential, service, and business customers, as well as agriculture farms, are still dominated by fossil fuels as primary energy sources. They are mostly equipped with steam and/or gas turbines, steam boilers, and water heaters (running on electricity or gas) for conversion units. The challenge to increase the share of renewables in the primary energy mix could be met by integrating solar, wind, and biomass as well as some types of waste with the fossil fuels. This work analyzes some of the most common heat transfer applications at total sites comprising users of the types just mentioned. The energy demands, the local generation capacities, and the efficient integration of renewables into the corresponding total site CHP (combined heat and power) energy systems, based on efficient heat transfer, are optimized, minimizing heat waste and carbon footprint, and maximizing economic viability.