The answer to 'difference between variable speed and single speed AC' is that variable speed air conditioners are more energy-efficient and provide better temperature and humidity control compared to single-stage, single-speed units. Variable speed ACs use a compressor that can run at different speeds to match the cooling demand, while single-speed ACs only have one fixed speed.
Variable speed ACs are generally more expensive upfront, but they can save you money in the long run through lower energy bills and more consistent comfort. They also tend to last longer and require less maintenance. Single-speed ACs are simpler and cheaper, but they can use more energy and may not provide the same level of temperature and humidity regulation.