Swimming pool heaters work by using energy sources like gas, electricity, or solar power to heat water as it circulates through the system. Gas heaters burn propane or natural gas, while electric heaters use electricity to warm the water. Solar pool heaters, on the other hand, utilize sunlight, making them eco-friendly and cost-effective over time. The best type of swimming pool heaters for you depends on your budget, pool size, and local climate. Gas heaters are great for quick heating, electric heaters are efficient for small pools, and solar heaters are ideal for sunny areas with extended swimming seasons.