Final answer:
The sun's energy is most effectively utilized by humans in the form of heat, which is used in various ways, such as heating buildings and powering appliances.
Step-by-step explanation:
The sun's energy is most useful to humans after it is converted to heat. While the sun does convert mass into energy through nuclear fusion, the vast majority of useful energy we harness from the sun on Earth is in the form of heat and light. For example, solar panels convert sunlight into electricity, which is then used to heat buildings, power appliances, and more. Moreover, the sun's energy is essential for life on Earth, as it allows for photosynthesis in plants, which is the foundation of most food chains. Lastly, the thermal energy from the sun also drives weather patterns and climate.