What are the odds that I click on a post I'm interested in and find something I wrote used as a quote?!?! LOL
When configuring amp hours and trying to decide how many panels you need I have found that .275/.325 x advertized watts on the panels gives you a realistic average positive amp hour number. I'm trying to find the credited source for this number and will acknowledge it when I do. However, in my real world testing, using battery tender style solar chargers, 10w up to 50w, I have found that formula to be pretty good in the South Eastern United States. Using that formula, .3 x 400= 120. If the formula holds true for larger panels, I would take that to indicate that your average weekly battery replenishment would be around 120 AH daily. Now, if you add up a realistic amp hour usage spreadsheet, you will be amazed at how quickly your actual amp hours add up; to the point that 120ah is not sufficient to run everything under the sun continuously. On a 12 volt system, a good way to get some average numbers that are close to reality is to take the listed amps of the device and multiply that by the hours of use per day:
Boat DC power requirments- Total AH per day of use= 44.7
Engle MB40 frdge/freezer- 36 WPH = 432 WPD= 36 AH per day
LED dome light avg .275 amps
Currently have 2. .55 ah x 6 hours= 3.3 AH per day
Standard Horizon GX1700B VHF. Standby- .45 ah= 5.4 AH per day
This was just the beginning of my boat. As I continue to outfit her, I have reached a point where I will no longer be able to maintain my batteries above 50% of their available amp hours on solar alone. If I choose to continue adding devices, I will have to supplement with either wind generation or IC engine usage. Remember, unless you want to replace your expensive storage batteries quite often, only draw down your batteries to 50% of their rated capacity. So if I have 400AH worth of AGM's, I really only have 200AH to continuously use. If I use 120AH a day. But my solar energy is only replacing 100ah a day, I theoretically will have 5 days before I need to start my engine. However, the plot thickens; this does not take into account losses in efficiency due to wires, connections and the corrosion of both. In addition, heat also causes higher losses. So ideally, you want to use the 50% minimum as an absolute maximum use.
If you use my list above as an example, notice that it does not take into consideration navigation lights, navigation hardware and auto pilot devices. My actual list is much much longer. That was a baseline for sitting on the hook.
You have to decide what features are important to you and then build a system to support those systems. The installation of the nice to have stuff and the pressing of the power button is the easy part.
Obviously based on my quote you've been reading the thread where we are discussing those very things.