Can you count signal energy equivalent in frequency domain?
Parseval's theorem applied to the signal itself:

$$\sum_{n=0}^{N-1}|x[n]|^2 = \frac{1}{N}\sum_{k=0}^{N-1}|X[k]|^2$$

So, if you sum the magnitude squared of the frequency coefficients of the DFT, you get the energy of your time-domain vector.

If you want power (i.e. energy per sample), divide both sides by $N$.