For exterior lights:
- I would give serious thought to LED Brake lights...not for power savings but the speed they light up. An incandescent is typically around 0.5sec to light up. An LED is typically around 0.05sec. That means drivers behind you have almost an extra half second to react and brake. Plus the good ones are brighter.
- Running lights...If you feel like it fine but power consumption isn't a big deal with the motor running, especially if you don't do a lot of driving at night they aren't typically on anyway.
- General outdoor illumination: This is where power consumption savings can be beneficial. These lights are on for long periods of time when there is no charging source active. Quality is important as some LED light sources create a harsh light that some people find uncomfortable but that's becoming less and less of an issue.