Specifying your hot water system will depend on your demand/usage and available power. Typically large households will require a storage cylinder to provide enough hot water on demand. Small apartments will be able to utilise an instant water heater.
Our recommended solution for most circumstances is a standing heat exchange cylinder. Thanks to its green credentials and the fact that in winter it uses the heat given off by your Sunflow radiators, and in summer uses the ambient temperature, to heat your water, it is the perfect choice.