Hi jennifer
Would have responded earlier but we have had little web access over the summer.
This topic is a complex and depending on ones knowledge can be very complicated. I am by no means an expert but have found that you need to be your own advocate with proper knowledge of the workings of off grid systems. By that I mean you need to gather some books and web sites and start to learn as much as possible and when it becomes over bearing take a break then get back into it. Proper understanding will save money and make your life more comfortable.
Fist thing is what lifestyle is it you will be doing to benefit from solar panels and where is it you will be when using them the most. For instance here where we are now in NH it would not be prudent to invest in a pricey system for the purpose of boon-docking (dry camping).
Nor would it be in the north west because there just is not enough solar hours per day.
We spend the winter boon-docking outside of Yuma AZ, one of the best places in the country for sun and this is where we count on our system to provide the majority of our electrical needs.
We have 2 panels totaling 270 watts and we also have an air x wind turbine that puts out 400 watts in a 29 mph wind. There is wind in the desert. We really need to double our panel array and probably will in the future but for now with great power management we get by from day to day in the desert by running the generator for an hour in the morning and maybe an hour in the evening to supplement. Understanding batteries is a big item. The debate on which type goes on but for us we use the AGM's by life line for these reasons:
They are CLEAN and stay CLEAN no having to be concerned about acid messes which will happen especially if and when you equalize them as you should from time to time. Also they recharge quicker, think about it, quicker recharge time means less sun time needed and less generator run time needed, (fuel savings!) they also will not drain down as quick.
All batteries will lose efficiency in cold weather by as much as 50 percent depending on how cold is cold. This needs to be considered when calculating battery bank size. We have 2 AGM's for the house and 2 AGM's for the chassi. Both sets of batteries were purchased within 6 months of each other which is a safe time to use together. I have the option to merge both banks if I want to double my battery bank BUT if I take power from both sides I need to know it will take more time to refill from eithe the sun or wind or genny.
you should start by figuring your total 24 hr usage. As batteries are rated in amp hrs I convert everything to amp hrs. We pull apx 21 amp per hr in the evening in the desert.
Your total need will tell you your total battery bank size but you may want to add a little more to make up for the not so sunny days and cold weather. Also figure using 50% less than wht the battery is rated at and you will double your battery life. Example: my 2 house batteries are rated at 225 amp hrs each which totals 450 amp hrs. I figure a safe level to pull them down to is half that before they need to be recharged to full and not partially full they need to be fully recharged before putting a load on them again.
A very useful item for monitoring batteries which I highly recommend to anyone that wants to know just where there batteries are is a battery monitor such as a trimetric battery monitor.
http://www.bogartengineering.com/
This after properly installed will tell just how many amp hrs you have used and how many amp hrs are left for use. It also lets you see the ACTUAL voltage. I say actual voltage because as I have a blue sky charge controller which I like but as with all controllers they are measuring the surface voltage and not what is actually in the battery, this is where folks can get into trouble because the monitor reads higher than what actually is, that is until the sun goes down and the panels no longer put out then the monitor and charger read the same.
Now the size of your battery bank and end usage daily will tell you what your panel aray size should be and if it requires a to expensive size then you need to make up the deficit in other ways, for us the genny. I can't stress enough the importance of this battery monitor. it also can monitor total amp hrs on a set of batteries over the life of the batteries.
Once you are ready for panels you need to know proper wire size. Some folks with large solar arays go to a 24 volt system which means they can get by with smaller wire. Copper = $$, Higher voltage is more efficient something to learn about. Don't worry the 24 volts gets changed back to 12 volts at the charge controller before it goes to the batteries.
Now you have the panels and wire you need a proper charge controller but my mistake here with lack of knowledge is I did not allow for expansion. My Blue sky controller is a 25 amp max controller, if I want to double my aray I also need to get a larger controller. A larger controller in the beginning would have saved me more now. Plus larger controllers also have other features that could be useful via what is called a version load control, more to learn about.
So now you have a proper sized Battery bank and solar aray to refill the batteries and wire size and charge controller and hopefully a battery monitor. Learn as much about batteries as you can call the manufacturer and get answers from them. i learned that the lifeline will safely take a 15 volt spike which happens with the airx wind turbine as I have cranked it up to put out more because wind is not a constant. The life line are pricy but after 4 yrs they are still very clean and if something happens to me my wife does not have to worry about the maintenance that flood acid requires plus ther is enough other stuff to keep me busy and have been enjoying not having to deal with the flood acid stuff. I did have them for the house side when I purchased the coach and they made a mess and stained the area they were in. Learning just what makes a battery different form others are helpful. Learn about the plate thickness difference in various batteries and the chemicals used. Newell uses these batteries for a reason. But depending on your usage just the recharge rate will add up to savings.
Remember, do not mix different type batteries nor batteries that are over 6 months of each other preferably less, this will just cause a bad situation which can be costly and possibly do damage
That should give you a start. I have found that most small dealers only know enough to get you confused and in trouble. My first mistake was with Solar Bill in Quartzsite AZ, he has or had good stuff at a good price but his knowledge was lacking, as I asked questions he walked away. Buyer beware.
Brad
Solar Panels
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