What you need to stay comfortable aboard depends on your planned destinations, the size of your boat, and your cruising style. Looking to venture to higher latitudes? You will want a robust cabin heater, such as a hydronic system from Webasto, which can heat the entire boat and your hot-water tank too. If you’re staying in more temperate areas, a bulkhead-mounted unit like those offered by Sig or Dickinson may suit your needs. And for tropical cruising, particularly if you’re planning to spend some time in marinas (or have a robust genset), an air-conditioning unit will be welcome on humid nights.