Symbolic gestures are all very well, but real gestures, however small, are a lot better. Here's a few ideas off the top of my head for things you could do on Saturday instead of turning off the lights for an hour:

- If you still use incandescent bulbs, buy some fluorescent or LED bulbs to replace them.

- If you heat your house in winter, and it's not well insulated, look up options for getting better insulation put in.

- If you're in the habit of driving when you could have walked or used public transport, try one of those alternatives.

- If you eat meat, try a vegetarian dinner on Saturday.

Any other ideas?