promote saving electricity (setsuden – 節電). One power plant has taken all the publicity, though the second Fukushima plant is non-operational, and other conventional stations are damaged. On top of that, west Japan can't export electricity to east Japan because the two halves work with different hertz. So east Japan is seriously short of power. It's already tricky, but in the summer months it could be looking more than tricky… see here.
So stopping all wasted usage, as well as experiencing the sometimes enforced scheduled blackouts in the areas around central Tokyo, have become a necessity. This site promotes making posters designed not merely for design's sake, but to put up outside your house or encourage local businesses to display etc.