Note: I recently bought some rechargeable NiMH Energizer batteries for my remote control airplane and now, because of this, I'm glad I got a good deal too (I was unsure at $18 per four batteries and a charger, but over 700 recharges that comes out to be about a couple pennies per four fully charged batteries which also outlasts all other batteries under continuous use conditions as well).
Source: Energy Savings Experiment at WalletPop.com