The Einstein’s photo-electric equation is based upon the conservation of

Einsteins photoelectric equations states that
$E_k=h\nu -\varphi$
where, $E_k$ is maximum kinetic energy of emitted photoelectrons
h is plank's constant.
$\nu$ is frequency of incident light
$\varphi$ is work function of metal.
So, it is clearly based upon energy conservation.