ahhhh... i wonder about this all the time... most people say dont. but i'm a thinker...
i would say it depends on where ur grow is at. if its in the basement, most likely not. if its on an external wall they can see it, but are they there? thats the real question...
if your worried about electric find ways to conserve and lower your bill at the same time, like changing to cfls and turning stuff off.. its really easy to offset power if you just try... and dont steal of course..