I am amazed at some of the cree leds and 1. how long they work on battery power and 2. how bright they are.
I went with the CFL bulbs in 2004 in our house in Japan and 2005 in our house in the USA (Daughter was living in our house here). IN both cases, from May through Sept, our electricity went down $100.00 a month on average. Part of the cost was the AC cooling of the incandescent heat.
Both in Japan and in the US I think I spent about $300 on bulbs at each place - to replace all incandescent bulbs through out the houses. Saved more than that in the first summer. We moved back to the US in Dec of 2010. This past spring I replaced all CFL bulbs with LEDs. We got very little change in utility bills but the difference in CFL to LEDs were noticeable, especially when immediately turned on.
That said, as mentioned above, I would start with replacing 120V lights to 12V. The 12V lights are bright. There are appliances being made that will work on 12V including refrigerators, and other small appliances. If I were rebuilding or young enough to rewire my house, I would go with a combo wind turbine and solar panels and convert what I could to 12V. BY the way, I had an American friend in Japan that was a fanatic about electrical safety and he worked at a couple of nuclear plants here in the USA. Over there, he wired his house for dual voltage and it passed their codes, and they are stricter on wiring than the USA in certain areas. They do not allow unsheathed neutral wire as we do.