It is interesting to know how other boaters are selecting equipment
and managing electrical power on cruising sailboats. Standard
production sailboats rarely have onboard DC power grids to support
additional electrical loads. Most extended cruisers and live aboard
boaters prefer to have conveniences like refrigeration microwave
ovens, computers and creature comfort items. There must be a limit to
how much daily electrical load that can be supported on a pleasure
size extended cruising sailboat, but what is this limit? I believe
that an average cruising boat's DC power consumption when at anchor
might be at least 50 amp-hrs per day. If equipped with refrigerator
add 10 amp-hours per cu. ft. of box per day. If additional 110 volt
appliances are powered from an inverter the total power grid will be
overstressed unless energy is generated from other than the a engine
alternator.

Here are some actual examples of cruising boats and how they managed
their DC power grid.
1. Twenty seven ft sailboat two people onboard with one cylinder
diesel crossed from England to Bahamas with no electrical system.
Navagation lights powered by Diesel fuel flame three gallons total use
of diesel in 27 days
2. Catalina 27 with two group 27 batteries 30 amp alternator on first
cruise after installing refrigeration unit batteries dead after two
days had to get a jump start from another boat. This problem was
repeated each time boat was used. Running engine several hours a day
did not solve this energy deficiency.
3. Thirty ft. sailboat two cylinder Yanmar engine with 60 amp
alternator and 4 gulf cart batteries spends 6 weeks to 3 months each
summer in Bahamas. Boat has standard basic electrical lights, VHF, and
Adler Barbour refrigeration. With the help of two 80 watt solar panels
mounted on top of Bimini engine only needs to be run every other day
to recharge batteries.
4. Forty four ft sailboat world cruiser on trip from Ft Lauderdale to
South Pacific. Boat equipped with both engine driven and 12 volt AB
refrigeration systems were connected to large holding plate in
refrigerator. I received a post card stating on 31 continuous days of
sailing the wind generator supplied all power needed to charge
batteries and operate refrigeration.
5. Local 36 ft sailboat with refrigeration tested in my book completed
circle trip to England with wind generator supplying all energy needed
on trip east bound, than lost generator overboard in English Channel
during storm.
6. One of the best truly live aboard boats I have worked with is a 60
ft plus two mast sailboat with very large refrigerator and separate
freezer. There is an engine driven refrigeration system freezing
seven holding plated when motoring. There are two air cooled 12 volt
refrigeration units maintaining box temperatures when boat is at
anchor which is most of the time. There are several energy sources to
support this boats DC power grid, two wind generators, solar panels,
prop shaft alternator and engine alternator.
7. My own 32 ft Watkins sailboat consumes around 70 to 100 amp-hr per
day when anchored out in summer tropical weather. I have a number of
110 volt fans running off an inverter and Yes I have Hybrid
refrigeration Engine driven refrigeration and 12 volt system freezing
three holding plates. I run the engine one hour per day to support my
energy needs consuming about 1/3 of a gallon of fuel. If you want to
see how my boat is equipped it is described on my web site at
http://kollmann-marine.com/Loreli.htm
8. If you are following Skip's Morgan 46 adventures on Flying Pig you
know his plan was to support all his electrical and refrigeration
needs including heating water with 12 volt energy. Skip removed the
engine driven refrigeration system replaced it with a 12 volt
Frigoboat unit. The large generator was removed providing room for a
battery bank. We are still not sure what his actual daily power needs
are but he seems to be managing his energy budget by trimming down the
load and running a small Honda generator when wind and solar power is
not enough. One good piece of information Skip provided if I
understand him correctly is the Hondo 2000 powering a 40 amp DC output
charger can rum 6 hours on 1/2 gallon of gas. I have a 3000 watt
generator that consumes 6 gallons per hour.