are christmas lights expensive to run

Not at all! They're actually quite energy efficient. Most Christmas lights are LED lights, which use much less energy than traditional incandescent lights. Plus, they can last for many years, so you won't have to keep buying new ones every season. And if you're really concerned about your energy usage, you can even find eco-friendly lights that use even less energy. So don't worry, you can keep the lights up all season long and still feel good about doing your part to save the planet.