A pure utility stock, that is operating well would normally pay out about 65 - 70% of earnings. MDU is not a pure utility and the E&P company eats the cash flow. This year they are paying out about 50% of net Income based on the 2013 estimate. Next years consensus estimate is $1.53, so 50% would be 76.5 cents yearly. They have never really set a goal so it is almost impossible to tell what management will do.
I think they paid the 1/2 cent a quarter increases just to keep the streak of annual increases alive during the financial crisis and subsequent Great Recession. I would look to a penny a quarter increase this year, maybe even 2 cents a quarter next year if they continue to grow revenues and profits.