In physics, the unit of energy in the system of natural units known as Planck units is called the Planck energy, denoted by $E_P$. $E_P$ is a derived, as opposed to basic, Planck unit. An equivalent definition is:$E_P = \hbar / T_P$ where $T_P$ is the Planck time. Also: $E_P = m_P c^2$ where $m_P$ is the Planck mass.
$E_\rho = \sqrt{\frac{ \hbar c^5}{G}} \approx 1.936 \times 10^9 J \approx 1.22 \times 10^{28} eV \approx 0.5433 MWh$, where $c$ is the speed of light in a vacuum, $\hbar$ is the reduced Planck's constant, and $G$ is the gravitational constant.
Planck Energy