While this isn’t a question I get that often, it is a great question nonetheless. Like most things catamaran cruising related, there isn’t a simple answer.
Most modern catamarans are optioned with Air Conditioning from the factory. If the boat you own or the boat you are thinking about buying has air conditioning, then it does in fact also have heat. That being said, there are limits to heating capacity.
There are two primary types of HVAC systems found on catamarans, reverse-cycle or chiller system. Categorically speaking, catamarans under 50ft have reverse-cycle systems and catamarans 50ft and larger tend to have chiller loop systems.Whether equipped with a reverse-cycle system, or a chiller loop system, raw water is circulated through the compressors similar to how a home HVAC system has an outdoor compressor that is cooled by the ambient air temperature.
What Laura and I learned while living in Annapolis, MD back in 2018, is that when the ambient air temperature drops below a certain temperature, the heat pump is not efficient at producing heat. So just like a heat pump losing efficiency in colder weather, the heater function on an HVAC system that uses raw water also loses efficiency. In the case of most modern marine HVAC systems it is when water temperature drops into the mid 50’s.
What if I plan on sailing where it’s colder?
If you decide you want to sail in a region where the water temperature constantly drops below the mid-50s, or you don’t want to run your generator all day long, the best option is a diesel heater. These systems have come a VERY long way over the last 50 years. They are incredibly safe, easy to install, and generate the most BTU output based on energy input.
We’d love to hear about your sailing plans, or the coldest weather you’ve experienced while sailing a catamaran!
