A: These systems work differently and the answer depends on climate, cylinder size and what else you are doing with water heating (eg central heating). Our general guidelines are Solar is best with larger cylinders and will give you the most efficient water heating. Hot water heatpumps are best when combining with central heating. We do not recommend intergrated hot water heatpumps in central north island or from Canterbury and below due to poor cold weather performance. Solar has a much longer life than a Hot Water Heat Pump (Guarantees are 10 years rather than 2 years).