Originally Posted by ReneJK
18000 btu roughly translates to 4000-4500 watt so a 2200 watt generator wont be able to run it as you are 2000 watt short and neither will your 3000 watt inverter as its 1000 watt short
While 1 watt is roughly equal to 3 btu-hr, you aren't directly converting electricity into coldness, so you can't do a literal conversion of the air/con rating into watts.
What you are doing is extracting EXISTING heat BTU from the inside air and transferring it to the water
the boat is sitting in. Imagine picking up a chunk of ice from outside and bringing it inside to cool down your drink, the energy you expend picking up the ice and carrying it inside is not equal to the BTU value the ice has for cooling
of the drink.
Now back to the question. We used to have a 12k btu that I measured at around 12amp @ 120v when running (or about 1450w). 18k btu is about 50% more so probably a bit north of 18 amps (just shy of 2200w) though it might not be exactly a linear relationship so this is a rough estimate.
Running it off solar
or wind...not for any practical length of time. 320w of solar
will generate around 1300w-hr per day. If you use nothing else, you have a little over 1/2hr of run time generated (1300w-hr/2200w). Wind will do a little better if it's a windy day but if it's calm hot and sticky, it adds nothing. (plus if you aren't using it as it's generated, you need a big battery
bank to store the necessary power)
Now to the portable generator, this is a viable option but likely not a tiny 2200w unit. Most manufactures advertise "PEAK" output. Continuous output is likely 1600-1800w, so likely not enough to keep up with 2200w continuous.
You are probably looking at something around 3500w with the soft start capacitor to run 18k btu.
PS: make sure to take safety
precautions using a portable generator. It can be done with reasonable safety
but it's also easy to be unsafe. In particular the CO from the exhaust
if you don't have a good place to direct the exhaust
. Then there is the heat from the exhaust and safe gasoline handling (similar to dingy motor