A technician usually installs a solar water heater in a few hours, on flat roofs. Of course this does not take into accounts special local requirements (particularly fragile roofs, need for supporting structures other than the one provided, etc) or laws (boiler hidden, panels disappearing into the roof, etc).

For these different scenarios the local authorized reseller will be able to give you the best advice. It might be necessary to call a plumber and an electrician to complete the installation.