solar panels

Re: solar panels

A good start is to figure out the $$$/Watt price... In the olden days (10-15 years ago), you where looking at $10 per watt.

8 years ago around $5 per watt. Today $2 to even $1 per watt... The "magical" $1 a watt for, a couple years ago, the goal of thin film panel manufactures--Which were about 1/2 the efficiency (need 2x the square footage of panels for same amount of power) and usually plastic face--Which can have less than 20+ year life in sun that we normally expect from glass panels (I am a pessimist regarding sun+clear plastics--they may last much longer than I fear).

And the caveats... Check for costs at your front door (shipping+handling+insurance). Shipping a pallet load (packaged from factory) of panels via truck is sometimes not that much more than shipping a single panel via UPS/FedEx/etc... Most panels are single weight tempered glass--Very easy to break if scratched or a hard knock. And using "standard shipping", around 140 watt panels are about the maximum size that can be shipped without going truck.

Note that on a $$/Watt basis, panels over ~200 watts are typically less expensive. And panels less than a 100 watts are typically much more expensive.

Today, you are looking at around $1.40 to $2.80 per watt (from our host).

Another thing to watch for when going >100 watt panels... Many of the "high power" panels are not standard "12 volt" Vmp panels (really Vmp~17.5 to 18.6 volts or so)... Meaning, that if you are looking at Vmp>20 volts or so, you may need/want to purchase a MPPT type charge controller.... Which is around 2-5x more expensive than a "cheap" PWM type charge controller.

If Vmp is too low, it may not recharge the battery correctly (especially in hot weather). And if Vmp is too high, you lose a lot of efficiency when Vmp is >> Vbatt charging (i.e., a Vmp=35 volt panel charging a 12 volt battery with a PWM controller will be around 50% efficient).

-Bill