The Kigali Amendment to the Montreal Protocol and the F-gas regulations in the European Union mandates a reduction in the usage of high GWP refrigerants, especially HFCs which are major contributors to climate change. This has popularized the use of low GWP refrigerants such as HFOs and natural refrigerants such as hydrocarbons, carbon dioxide, and ammonia. Hydrocarbons have been shown to have superior thermodynamic performance compared to most other alternatives, however, they are either highly flammable or toxic and hence have strict system charge limits. Many studies have shown that a majority of the system refrigerant charge is present in the heat exchangers (HXs), i.e., the evaporator and condenser, and optimizing these components can have the highest impact on the overall system charge. This paper begins with a review of different charge reduction strategies as they pertain to the design of HXs for heat pumps. This is followed by an analysis to quantify the minimum theoretical charge required in a HX to achieve a particular capacity. While the main focus has been to maximize heat transfer rate and minimize internal volume, the actual design variations include various hydraulic diameters as low as 0.8 mm. Other investigations include the use of sophisticated techniques such as shape & topology optimization and machine learning to arrive at novel surfaces that are superior to contemporary designs, with charge reduction of up to 50%.