Dew point is the tempurature the air cannot hold the weight of the water in it. The water then begins to condense and form droplets. This tempurature is always below or equal to the air tempurature.
Propane prices. Maine (ME) propane users spent an average of $2.724 per gallon over the 2012-2013 heating season. This is slightly higher than the 2.436 average for the country as a whole, for the reasons explained above (distance from major supply source, colder climate, higher demand).
Propane is measured by the gallon so propane is priced per gallon. During the 2011-2012 heating season propane prices ranged from $2.74 to $2.88 per gallon, meaning that a 500-gallon tank cost between $1,100 and $1,150 to fill. Propane compared to other energy sources. That propane prices have increased over the last 10 years does not mean that, compared to other sources of energy it is necessarily more expensive.