Mary Fisher wrote:

The details are unimportant. The principle is right.

Weeel, I disagree there. The detail, in this case, is everything.

If you have a room with a PC (200W) and a large TV (100W) in it,
then you're dumping in say 300W.

Say the room has a south facing window, 4'x5' (total area
~2m^2), then on a sunny day the light coming in through that
window can contribute a couple of kW to the room.

That's a much more significant heat input. Fitting a blind will
have a *much* bigger effect than switching off the PC and the TV.

That isn't to say it's not a good idea to switch things off when
not using them (except PCs, but that's a whole other kettle).
Just that in terms of keeping a room cool in the summer, they
are minor points.

--
Grunff