View Single Post
Old 09-18-2011, 11:31 AM   #19 (permalink)
Master EcoModder
IamIan's Avatar
Join Date: Dec 2010
Location: RI
Posts: 692
Thanks: 371
Thanked 227 Times in 140 Posts
Originally Posted by Arragonis View Post
The cost per unit of energy produced is 10-20x that of conventional power.
Of course it varies significantly from place to place ... and some places RE ( solar etc .. ) is much more expensive per unit energy than what the grid sells for... but in other places RE ( solar etc ) is already significantly cheaper per unit energy than what the grid charges.

My opinion is that is is better to crunch the real numbers for a specific proposed location and installation ... some will be a good investment others will not.

Let me know if you see an obvious errors in this line of thinking bellow ( or if you need additional detail of any parts ):
  • Most PV systems today come with ~20 year power warranties to 80% of initial rated power ... Although it will produce more than this we can be conservative and assume a ~20 year average of ~80% of Initial power rating.
  • The Cost of 'conventional' grid type power varies significantly from place to place ... According to the EIA, the average price per kwh of grid residential energy in Hawaii in January 2011 was $0.30/kwh , but at the same time was only $0.0691/kwh on average for North Dakota residential energy ... so there is a huge difference in what people pay for the same amount of a kwh of electrical energy.
  • There is a significant difference in RE potential , especially solar from location to location... the EIA yearly average of solar hours per day ( 5.8 Fixed position , 8.0 sun Tracking ) for Kahului HI , and ( 4.9 Fixed , 6.6 Tracking ) for Bismark ND.
  • 1 watt of installed PV power in Kahului HI will produce an average over the 20 years of it's power warranty of more than ~33 kwh for the fixed position system and more than ~46 kwh for the sun tracking system The same scenario in Bismark ND results in more than ~28 kwh fixed , and ~38 kwh tracking... so there is also a large difference in potential solar energy in the different locations.
  • To get the same energy the grid would charge you:
    • Kahului HI 33*0.3 = ~$9.90
    • Kahului HI 46*0.3 = ~$13.80
    • Bismark ND 28*0.0691 = ~$1.93
    • Bismark ND 38*0.0691 = ~$2.63
    So there is also a large difference in the break even point with the grid... In some places PV solar is already cheaper than the grid if it can get installed for anything under ~$13.80 per watt ... and other places it would have to get down to under ~$1.93 per watt to be cheaper than the grid.
  • Although the installed cost of PV per watt will also vary depending on the specifics of location and install etc ... the last I read ( 2011 Berkley Lab report # LBNL-5047E ... I've included a picture of the graph bellow if you don't have that report ) the 2010 average cost of installed PV per watt in the U.S. was ~$6.20 / watt ... which will make it more expensive per unit energy in some places ... like Bismark ND ... and less expensive per unit energy in other places like Kahului HI.

So my only point in the above is that ... it varies depending on the specifics of a given context ... RE ( solar etc ) is not always cheaper or more expensive than the grid ... sometimes RE is cheaper per kwh of energy ... sometimes the grid is cheaper per kwh of energy... it isn't a black and white issue anymore.

The other aspect of RE vs Grid ... is that as seen in the attached picture ... the $/Watt of installed PV has been going down at a significant rate.
Attached Thumbnails
Click image for larger version

Name:	USCostInstalledPVWatt.JPG
Views:	12
Size:	55.5 KB
ID:	9448  
  Reply With Quote