A friend is building 5 en-suites above his pub. An advisor has said he needs a 64kW gas boiler to heat 7-8 radiators and an 800-1000 litre water tank to make sure guests have hot water when they need it. This seems way over the top to me - especially as it's not guaranteed that there will always be 5 guests. Is it possible to run two 300 litre tanks in parallel for example so that the second is only heated up if needed? If he did run two in parallel, would he still need a 64kW boiler? Any ideas welcome. Thanks