Trying to Make Sense Out of Green Tags

Try to figure out how buying green tags from BEF compares in environmental benefit to doing your own PV system.

 

BEF Bonneville Environemetal Foundation

https://www.greentagsusa.org/GreenTags/index.cfm

 

BEF FAQ's:

https://www.greentagsusa.org/GreenTags/faq.cfm

 

 

A 500 KWH per month customer is trying to decide whether to build a PV rig to satisfy his full demand, or buy green tags:

 

CO2 generated by 500KWH per month of Montana mix power is:

 

(500 KWH/mo)(1.5 lb/KWH) = 750 lb /mo or 9000 lb/yr

 

 

PV system:

Per PVWatts it takes a 4.48 KW peak power PV rig to make 6000 KWH/year

 

This would cost about:

(4480 pkwatts)($9/w) = $40,320  one time cost

 

Should really include some yearly maintenance, but ignore for now.

 

--> above ignores the value of the generated electriicty!!

 

BEF tags:

At $2 per 100 KWH /mo, it takes 5 tags = $10 /mo, or $120 per year

 

If I were to invest the 40,320 in a 5% CD, I could earn $2016, or enough to offset (2016/120) = 16.8 times as much CO2 using green tags as with doing my own PV rig?  Is this true?

 

 

Questions:

If I do my own PV rig, I know its going to be built, and that it will be preventing the generation of 9000 lbs of CO2 per year for many years.  If I buy an equivalent amount of green tags, how do I know how much CO2 these will actually eliminate?

There calculator gives an answer, but how is it calculated?