Iowa’s largest natural gas utility held a briefing today to explain the “supply and demand” problem, which is causing the dramatic spike in heating costs. MidAmerican Energy spokesman Kevin Waetke says some natural gas suppliers shut down production because demand in the past two years was down, and they weren’t making money. Waetke says it’ll take up to two years to match supply with the demand.Waetke says four interstate pipelines are bringing natural gas into Iowa, but he says some other states don’t have that level of competition, making prices even higher.