Most guides to determining your energy consumption on a daily basis add the amp-hours of all devices to give total consumption. This is not actually very accurate as I have found recently.

Here are two good links to websites that help you add up your power usage:

RV solar has a great deal or real information including a page with a consumption chart to fill out.

For really getting into solar for the home and RV, the best compendium of information is in all the back issues of Home Power magazine - free on the net.

Now here's what I have learned:
Fans, such as the fantastic fan, should not be added to your total amp hour usage. Any device that runs in the sunny afternoons are basically running FREE unless the batteries are flat exhausted.

Why: The answer lies in the way that your battery bank charges. Say you have been running your normal electric load for a day and a night and the sun comes out the next day bright. The batteries are showing a 12.08 DC voltage which is about as low as I get over two days of usage. At that voltage the batteries can be charge at a rate of 1/10 their capacity in amps- so for my 440amp/hour battery bank I could charge at 44 amps with no overheating of the batteries. Since my solar panels are putting out max at about 24 amps (in the summer in direct overhead sun), I am in no danger of hurting the battery bank. However at that voltage the battery will only take the 24 amps for a few hours and then I see that the voltage is now approaching 14V DC. At that point I'll see that the batteries are only accepting about 8 amps instead of 24amps. What happened to the other 16amps? They are wasted because the batteries are getting near full charge and can't accept.

I find myself looking of things to turn on when that happens so that I can use the 16 amps that are not being used. I swear I'm going to put a revolving radar antenna on the top of the airstream just to have it swing around to use some of the wasted juice.

But really, there are some devices like a Fantastic Fan that runs at exactly this time of day, usually in the afternoon as the temperature inside the airstream rises. Since I've got 16 amps to waste on something, the 3 amp maximum draw of the fan is nothing. I know look for things to run during this period. THis is a good time to do computing if I'm tired of the sun. Also it's a good time to watch a video, or run the microwave.
Every amp that is used now would never have been stored in the batteries anyway, so they need not be added to your normal usage. In fact since there is loss in charging a battery and loss in using the electricity, you can make a case that using one amp in this surplus period is equal to using 1.2 amps later if you had to take it from the battery.

To sum up: Device used on a sunny afternoon when the batteries are nearing full charge are "free" electricity. Anything run then that is less that 1/2 the total amperage that your array puts out, would never have been stored anyway. So do add these devices into your computations.

As an example I currently find that my ratio of 360 watts of solar panel (22 watts of pintail amps) to 440 amp-hours of battery capacity is actually too much solar panel amps for the battery bank size. I am charged up almost always before noon, even in the winter in Oregon.
So what can I do - well I can take more things of the commercial power grid - I could put my .9 amp 120V refrigerator on an inverter and run it all the time from solar. I'll write more about this experiment later.

More about standard cheap small electric refrigerators - the little apartment sized refrigerators you see at discount stores like Home Depot.
I replaced the huge, heavy, gas - 12V electric refrigerator that was stock equipment in my Airstream - as it didn't work and these gas absorption refrigerators seem to be one of the MAJOR problems of all RV's regardless of age.
So I checked out the amperage draw of the small cheap refrigerators and found that I could get one more than big enough for me - apartment sized - and only draw slightly less than 1 amp at 120V AC. This works out to about 10 amps draw from my battery bank through the inverter to 120V. However that turns out to be bullshit. When on my trip in March I initially thought I just would live with the fridge as I didn't want to have 60 amp-hours or more per day just used to keep a minimal supply of food cold. But it turned out that I had so much surplus energy that I decided to run the fridge from my 400 Watt continuous 800 Watt peak inverter.
Imagine my shock when the fridge consistently overloaded the inverter. That means that I was taking at some point more that 40amps, not 10, during the compressor start ups, for long enough to overload the protection circuits on the inverter. That is not 10 amps - that's over 40 amps at 12V. Once past the start up I was able to mesure an average draw over over 12 amps.
The answer to all this is replacement of the fridge with a thermoelectric cooler with about a 2am draw. Smaller in cubic feet, with much more insulation, these coolers turned refrigerators are made to operate directly on 12V, and will be perfect for my use.