It's fascinating how much data is publicly available. Here, for instance, is a summary of key data that describe the UK electricity market, including demand and generation by fuel type.
Well, apart from putting various fuel types into perspective, and maybe settling a few arguments, it's worth reflecting that the Hawthorne Effect was named after the electricity plant in which it was first documented. Henry Landsberger found that workers' productivity improved when he measured it to study the impact of light levels on their work, but declined again when his experiments ended. That suggests that when people know you're measuring their activity, it improves.
Alternative energy-generation measurement widget, anyone?