For a major overhaul, consider installing photovoltaic cells on your roof, hydronic radiant heating in your floors, double-glazed panes in your windows and low-flow toilets in your bathroom.
But there is good reason to think that the market has not yet peaked: the northern hemisphere's winter is only now approaching, heating oil stocks are at extremely low levels on both sides of the Atlantic, and the price of natural gas (oil's chief rival for home heating) has lately gone through the roof.