Dashew has a bit of the discussion here about the cost comparison, of course with fuel costs down to $50/barrel the cost equation may have temporarily shifted back to sailboats:
"With fuel prices flirting with $100 per barrel, are you concerned with the cost of cruising on the FPB?
When we first looked at designing an Unsailboat we spent a lot of time running operating costs numbers, looking at cost per mile, and per year, and relating these to different speeds. Since we had never done this with any of our sailboats we decided to go back and check what it cost per mile for their operation, taking into account amortization and repair of sails, rig and rigging maintenance, and the engine room gear. Turns out that the FPB running at 11 knots is about 60% of the cost of operating a sailing yacht like Beowulf, so we stopped worrying about the per mile costs.
When we stopped in Hawaii to rest up and top off our tanks before our leg to California, we paid US$3.00 per gallon, the most we’ve seen so far for diesel. This works out to $1.82 per nautical mile running at 11 knots and burning 6.7 US gallons per hour. Add in another fifteen cents per mile for oil changes, a yearly check by a mechanic, and rebuilding engine and transmission at 20,000 hours and it is still much less costly than sail.
We are headed to the UK this spring and will be paying probably double what we’ve been used to for fuel. We can offset this by slowing down from 11 knots to nine.
The matrix above is for the FPB 64 at various speeds with an allowance for auxiliary consumption (generating power and hydraulic loads). This covers only fuel costs and will show the relationship between cost and speed.
One other factor to consider is fuel capacity, range, and the ability to wait until you get to places with better fuel prices. For example, Wind Horse sits with half tanks right now because a couple of hundred miles south, in Ensenada, Mexico, we can buy good quality diesel for a third less than where we are presently located. The last time we filled the tanks was on the Alaskan Panhandle, a long way away!
There is much more information pertaining to this under “Range” on the sidebar above."
Source:
SetSail » Blog Archive » FPB 64 – FAQs