Capacitors do not dissipate power

[sadpony]

"capacitors cannot dissipate power, even though current can flow through them. because the voltage and current are 90° out of phase". I read this in a book but couldn't understand its meaning. Can anyone explain it to me.
Thanks in advance

 

[skitzin]

I always understood it as:

The power is V x I x cosine of the phase difference between V and I and since the cosine of 90° is zero, the power dissipated is zero.

 

[dick_freebird]

Of course this is an idealization and only true of an "ideal
capacitor". Real ones have conduction losses in the plates
and dielectric losses in the insulator. And while the capacitor
(ideal) may not dissipate power, the current it imposes will
cause that power to be dissipated in the source.