I sort of agree with the throw the spreadsheet away argument.
A modern live aboard yacht has so many extra bits I doubt you could work it out,
My gut feel is this.
I need about a 120 amp to 140 amp hr per day.
About 60% of my power goes to running my danfoss fridge. 6.5 amps in use 40% duty cycle. Measured with stop watch and clip on amp meter.
Next are the computers
. Two laptops. The asus eee is about 1.5 ah 20 hrs a day.
Asus eee with video processor abot 3 ah 10 hours a day.
Fans we have 7 Camfro 757 fans. Usually two on. I estimate half a/h each.
Lights mix of fluoros and Led 3w to 18w in kitchen.
car stereo about 1.5 ah in use. .3 ah on stand-bye or 8ah for full day if not used. These phantom loads are crazy, So I turn it off with its own switch. It means you loose presets etc .
Plus we run a heap of a heap of other stuff. ie 1500 watt inverter
. for printer, microwave, vacuum.
My belief is "do not be a boat that's stingy on power. " I hate being on boats were people follow you round and switch off lights, fans, devices etc".
Sure don't waste energy but to go without some thing you want on a boat is really bad for morale.
I power all this with 470 watts of solar which on a really sunny day will put in 26 to 27 ah into flat batteries. By afternoon on sunny day 18 to 23 ah.
To help with cloudy rainy days I added a aerogen 4 wind generator
. This has been a fantastic addition. Absolutely useless in the tropics a lot of the time, but when it gets cloudy and stormy and solar input drops to a third. The wind gen starts kicking in between one and 3 ah. Multiplied by 24 hrs and it nearly makes up for the loss of solar.
Before I installed the windgen I would need to start my engine with 50 amp alternator and smart regulator
every say 7 to 10 days.
Now with windgen its really rare only when we need vacuum cleaner thru inverter
I would say if you can afford it a 70% solar 30% wind combination would be ideal in the tropics. Now that I have aerogen 4 I have thought about one less solar panel hanging off the back of the boat.
In the dry season when we have excess solar power we run the pur 35 watermaker
almost every day for 4 to 8hrs as well to make between 20 to 40 litres of water
. Its magical looking at the solar panels
as the watermaker tricles water
into a water drum. Again being on a boat stingy with water is also horrible for morale.
I have made detailed measurements and analysis of my devices power requirements and my usage and after 10 years afloat doubt i could accurately spreadsheet it.
For batteries I have 460 ah of truck batteries. I usually get 3 years out of them. I prefer n120 as they are easier to lift
. I cannot imagine paying twice the price
for trojans and getting 6 years out of them. A cruising boat is a horrible environment
A short circuit, some thing dropped on them, forgetting to check water; running dry, faulty regulator
over charging them, failing all by them selves early. Six years is too long a payback for me.
In my system I only use the batteries at night as wind solar powers everything during the day. So in theory I only need to power about 12 hours on batteries.
After about 2 days of cloud no wind I have to start the engine. Here in asia
its only one month around October / november that is bad the rest is just a few days of cloud.
I am now delighted with my power system and now consider it a finished project
and don't think about improving it any more.