Looking at the joint task analysis for non-financial benefit analysis it says to know how calculate CO2 avoidance, tons of coal saved, water saved, miles not driven, etc. Is that really something they would ask us how to calculate? Tons of assumptions go into each of those and several vary by geographic location. Any particular rules of thumb to remember for them or is it more likely they would give us all the inputs/assumptions and just ask us to calculate them based on lifetime kWh production of the system?
When I took the test these environmental questions were obvious and the answers are easy if you know how to do conversions. There are some examples in the book.
If they give you X pounds of CO2 per kWh, and tell you how many MWh were used, convert MWh to kWh and then multiply by X pounds of CO2.
They are not going to expect you to memorize how many pounds of CO2 are produced by a fossil fuel plant in Hawaii vs. a coal plant in North Dakota.
When I looked up the conversion for the book, I ended up at the EIA website:
It is interesting to know that it is in the range of 1.2 to 2.2 for fossil fuels according to EIA.
There are plenty of other websites that will give you different numbers. I'm sure you can find some fossil fuel funded foundation that will tell you PV pollutes more than clean coal. The funniest one I heard was from a Coursera course where the teacher said that wind energy leads to global warming because wind turbines slow down the wind which cools the earth. Very funny. He was very pro-nuke.
PV takes about a year to offset the energy that it took to make the PV system, longer if your crew drives stretch Hummers to work. This energy is getting to be less as the process is more efficient and less silicon is wasted.
From HeatSpring.com NABCEP PV Technical Sales Exam Prep Study Group