PORTLAND – The average price of retail gas in Maine has risen almost 5 cents in the past week to $2.18 per gallon. GasBuddy’s survey of more than 1,200 gas outlets in the state shows the retail gas price had gone up by 4.6 cents on Sunday. The national average went up by 3.7 cents per gallon in the same week and ended at $2.16 per gallon. Gas prices in Maine were 33 cents lower per gallon than they were a year ago.