In residential heat pump systems, the motivation for secondary loop systems is to allow for the use of flammable or toxic refrigerants with lower global warming potentials than the currently employed HFC refrigerants. The addition of radiant panels as integral building components (embedded in concrete at construction or attached to the underside of wood flooring) is becoming more common. Combining the large surface area of the radiant panel and an efficient primary loop, a hydronic secondary loop heat pump system can greatly outperform a conventional air-to-air heat pump. The improvement in coefficient of performance is as much as 38% over a conventional air-to-air heat pump when the secondary loop hydronic system is employed. Due to the large area of the radiant panel, the condensing temperature of the primary loop for the hydronic secondary loop heat pump can be reduced by as much as 5°C at high ambient temperatures.