How to Heat Water Using Solar Energy Solar energy is energy given off in the form of light and heat. There are many ways to turn this into energy we can use, from the high- to low- tech. This is a very low-tech and cheap method of heating water while running it though a garden hose. Cut the bottom out of large plastic bottles, the wider the better . Thread the bottles onto a hose . Try to get enough bottles to cover as much of the hose as possible .hose out in full sunlight, run a little water through it to make sure there is water resting throughout the length of the hose . Wait about half an hour for the air in the bottles to heat up . Run the water through the hose slowly and it will come out warm .Finished.by matrix technology.