I’m a bit of a numbers and finance nerd, a tech dilettante, and reasonably concerned about the environment (although I’d call myself a conservationist, not an “environmentalist” because like most people, we don't want too much inconvenience!). We just finished our first full month of having switched just EIGHT light fixtures to LED bulbs — the warm 2700k color temperature and “instant on” make them very similar to incandescents, and nothing like those crappy, cold, slow CFLs that they replaced. Our average month of May over the prior four years has ranged from 33-45 KWh per day (an average 38.5 KWh) which includes three outside fixtures that stay on all night for security. Now that we’re nearing the end of May, my reading yesterday shows we’re down to almost 30KWh/day. That’s about 70 cents a day of savings vs the previous 4-year average (using actual rates from the bills in our 2600sf house built in the 70s). There are other factors, naturally, such as seasonal A/C usage...but I’ve also been working from home, so there’s lots additional PC usage, as well — that’s why I’m doing this year-over-year. This 8-pack of bulbs appears to have paid for itself in just one month, to say nothing of the reduced coal usage at the plant :D