I think Cuppa is on the money. Going to be an interesting debate this weekend, however something I have always kept in mind for camping power, solar, etc is that there are some things that are fact (physics), some things that are myth (or just plain incorrect) and some that come down to use, location and quality.

For example:

Fact - the laws of physics determine such things as watts, amps, volts, losses, etc and their calculation. These are inviolable and true.

Myth - heaps of them out there and generally debunked by the above.

Use - this is where it gets interesting. There is no one size fits all (some come close) setup as everyone has different needs. Things like location and season determine amount of sunlight hours if solar is a consideration. Size of fridges, beer consumption (ie how often a fridge is opened 'cause you don't open them for any other reason right?) and lighting setup, other accessories, amount of time used, etc all determine power requirements.

I have found in the past, and I think threedogs advocates this as well, that putting together a list of your power consuming devices is the first step. Second step is working out how long you need to be self-sufficient for, third step is working out what type of camping/use you require. Ie - are you totally "off the grid" for weeks at a time, or do you need a fridge to run in the back of the car until you get to that powered campsite? Do you need a mix of both - in which case variable setups are a good option. Cost is another factor to consider as well.

Sorry - haven't really added to the solution (as I think there are different horses for courses) but hopefully some food for thought on some of the considerations.

For what it's worth Cuppa's post above is very, very useful and a very good rule of thumb in my opinion based on physics, use and experience.

Jas