I once went for the first time to visit a Dutch acquaintance and before I entered the bathroom for a shower I was asked "not to take a long shower because of the electricity costs."
I am Dutch and I would also need a moment to process that request. I would never ask a guest to shower short because of the energy cost. Unless, of course, they stick around for a year and tend to shower for 2 hours each day. This is more about being frugal than being Dutch.
Dutch showers are as a general rule not electricity heated but gas, and those that are electricity heated have typically really old boilers that take forever to warm up, likely the host meant that they too would like a shower later.