A bit late to the party but i wanted to back this up by linking to the relevant chapter from the fantastic book by David MacKay: http://withouthotair.com/c16/pa

A bit late to the party but i wanted to back this up by linking to the relevant chapter from the fantastic book by David MacKay: http://withouthotair.com/c16/page_96.shtml http://withouthotair.com/c16/page_96.shtml The chapter is only 4 pages long and he quickly works out that if done sustainably, even blanketing the entire country with geothermal plants could provide at most 2 kWh/day per person in the UK. Current consumption is about 125 kWh/day per person. So even without the capex argument, it is just not a very efficient source of energy long-term.