Your second question... NO you do not need a 1500 watt inverter
. Most of the time in my travels I never used the larger inverter. I used my 400 watt inverter. You will find that is a good size for MOST items on a yacht, except the power hungry microwave oven
, if you happen to have one of those.
Most boats do not have a coffee maker unless we're talking cats of 44 feet and larger. Then they also have gensets you are exercising probably more than you want to anyway. Figure out you largest power consuming item, or items you may want to run at the same time.
Target you inverter size for 50 to 100 watts RUNNING, above that number. Say you find you have a 540 watt item, and all else is less power consuming, then a 600 (with a 1200 peak for starting current) would be a good target, but you may find it easier to get a 750 watt. Most inverters come in "popular sizes" these days, so you'll more than likely find it easier to just get whatever one is above what you need minimum and be done with it.
CHARGERS are another issue. If you downgrade the size of an inverter, if it happens to be an Inverter/Charger combo, that is NOT a good thing for your bank. It will take much longer to charge up the batteries
going smaller on the charger size, nor are there many of those in smaller inverter groups anyway.
But then again, there is no reason you cannot separate the tasks into individual devices, which is what we did in the old days. The chargers were around long before inverters were popular on boats, and everything we used on a boat was DC, which is still your best bet efficiency wise, if you can get DC based equipment
and limit you AC powered stuff as much as possible.
I have had TOO MANY clients with Xantrex units whose battery
charger failed, but the inverter still worked (manually firing it up) add a battery
charger and ran that way even after the inverter chucked its cookies. There is a good reason boat manufacturers were installing Dolphin chargers and separate inverters in Catamarans from the factory.