Power or Energy Signal of x(t) = u(t)
To calculate the energy of a continuous signal you use the equation:  $$E_\infty = \int\limits_{-\infty}^{\infty} |x(t)|^2 dt$$   and for the power:   $$P_\infty = \lim\limits_{T\to\infty} \frac{1}{2T}\int\limits_{-T}^{T} |x(t)|^2 dt$$  If your signal has finite power ($0&lt;P&lt;\infty$) then it's a power signal. If the signal has finite energy then it's an energy signal (Notice that a signal can be neither type but can't be an energy and a power signal at the same time).