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).
Fireplaces to use 1-3 gallon of propane per hour; The Average Cost of Propane Per Year. The average cost of propane per year (for homes that use propane for heating plus other other appliances) is $2,000-$3,000. While this is more expensive on average than electric, it is less expensive than oil and more efficient than both.