Can I use my old hot water tank?
If you already have a solar hot water tank, i.e. one equipped with a solar heat exchanger and a temperature probe location at the same level as the heat exchanger, then it can be connected to solar panels.
If this is not the case, you will need to buy a special tank which will replace your traditional water heater. Your installer will be able to advise you on the best replacement for your current equipment.