If you've got the electron temperature and electron number density and you're assuming a maxwellian distribution, you can get the average energy = 3/2 kTe, (so for Te = 1 eV, average electron energy 1.5 eV). Then multiply by the number density and plasma volume to get a measure of the total energy in your electrons.
Depending on your device you may have gradients in the density or temperature, so you will want to use average values over the volume for a rough calculation.
Also you still have energy in the ions: the number density is likely the same as the electrons if it is quasineutral plasma, but the temperatures may be different depending on your device. And if not fully ionized, you've got neutrals.