$1 per watt is a pretty good price, and I would have been really happy to find a solar system at $3 per rated watt when I was shopping back in 1999! I paid $750 for a 90 watt kit back in 94, and $375 for a 75 watt panel in 97. By 2000, the price dropped to $429 for my pair of 120 watt panels. I was somewhat shocked to see in 2011 that prices where near $1 per rated watt at this place.
SunElec.comYes you will have to wire several 100 - 150 watt panels together to get the desired wattage, and still not have to relocate any roof vents. Shading with a larger solar system is less critical, because you will reach 'full' anyway by 3 pm, so if shading caused it to take another 15 minutes, it really is no big deal!
I had a PWM controller back in 94 and it worked great. By 1999, MPPT was "The thing to have" however even though my SB 50 amp controller has worked flawlessly, I am not so sure that MPPT will actually provide 10% more amperage to the battery. Solar panels tend to flow more amperage as the voltage output needed to the battery drops. MPPT increases the input voltage and then changes that increased input voltage to increased amperage into the battery. So say there are 10 amps at 15 volts going into the controller (150 watts) MPPT can convert the output to 12 amps at 12 volts (144 watts). (just a quick example that my brain can figure the numbers at 6 am). However my 15 amp PWM controller put out 7.5 amps with my 90 watt system when it was only 25F outside, we where camped at 4,500' elevation, and the battery was at 12.0 volts in the morning. Sun was reflecting onto the tilted solar panels, and it was mid-November.
For my money, the cost of 12 volt panels are so low that installing a $700 system, I would spend more on the panels and less on the controller. So PWM controllers will work fine. You can get a 10 amp PWM controller for about $14. You can wire one to each pair of panels, and not worry about shading effects, as one or two of the controllers will be in full sun.
For panel mounts, I cut 6" long 2" angle aluminum from home depot. I drilled 3 holes 3/16" for #10 screws into the roof, and 5/16" hole for a 1/4-20 bolt into the panel frame. Rubber roof sealant completed the job.
I would no longer recommend tilt arms. Just to much hassle to go up on the roof and move the panels around each day and before leaving to go back home. It would be easier to work 4 more hours, and buy a 100 watt panel, than to tilt the panels twice on each camping trip, and the more walking on the roof, the less 'good' that can happen to the roof. I used to tilt my panels on camping trips longer than about 3 days, but now do not tilt them. I would rather run the generator for a few minutes per week, it needs to be run once in a while anyway.
Reflecting back on my system cost (about $3000 including extra batteries, Trace inverter/charger, all the wiring and above panel costs, I can safely say it has paid for itself at least 3 times. Just by saving $10 a night in campground fees, I saved $3000 in the first 10 years that I had the system. Between 2004 and 2006, when I started full timing, I also spent about 300 nights in the RV, saving power then as well. While full timing, I would seek out free camping places, and again spent 365 nights in the RV, rarely using a campground from 2006 - 2008. And I can sell all this equipment for some amount of money, even though it is 20 years old and still working around 90% of it's original rating.
Good luck! and have fun camping!
Fred.
