Who is in control of the Department of Energy?

I'm curious to know who exactly holds the reins of power within the Department of Energy. Is it a single individual or a group of officials who make the ultimate decisions? And furthermore, what are the mechanisms in place to ensure that these decisions align with the best interests of the nation and its citizens, especially when it comes to matters related to energy policy and regulation? It's important to have clarity on these matters, as the Department of Energy plays a crucial role in shaping the future of our energy landscape.