In short, ASIC's are 99.9% efficient at converting electricity to heat.
Heat is the least useful form of energy, though. The best solution is to produce less by consuming less electricity in the first place.
Every new generation of ASIC is vastly more power efficient. Can the same be said for every bank branch or finance employee?
Bitcoin enables efficiency gains orders of magnitude above printing, distributing, and then finally destroying billions of notes of paper currency.
This is just STEP 1:
https://www.youtube.com/watch?v=eaBapDvfwFwDuring Fiscal Year (FY) 2013, the Bureau of Engraving and Printing delivered approximately 26 million notes a day with a face value of approximately $1.3 billion.
During Fiscal Year (FY) 2013, the Bureau of Engraving and Printing delivered approximately 6.6 billion notes at an average cost of 10 cents per note.
Over 90 percent of the notes that the BEP delivers each year are used to replace notes already in, or taken out of circulation.
Between the Fort Worth, Texas and the Washington, DC facilities, approximately 9.6 tons of ink per day were used during FY 2013.
http://www.moneyfactory.gov/uscurrency/annualproductionfigures.html