I would agree they seem a little low, but beenthere usually knows what he's talking about.
As far as doing the calculation, the rates, and intervals are already accounted for, all you need to do is add that % to those total dollar numbers.
If he had 60 and you're saying 64, then its about 6.5% higher cost.
Take his 1200 dollar number, or whatever they were and add 6.5% (I think 6.25% to be exact.
So, take 1200*1.0625 = 1275. simple
Yes, the 64 is per hour, but if all those energy dollars given include all that based on 60 per hour, then its like saying, for every hour, its just 6.25% more, so overall, 6.25% more than the big number.