Ive been using a 3kw over the winter, I havent been bothering lately as I cant see the point.
If I put it on for 12-13 hours it'll start to get hotish after the first few houses but I cant see the value in paying £6 per night , that over £80 per month.
The one place I saw a benefit was algae which came off easier, other than that it was just "nicer" to work with, thats all.