Mahtowa, Minnesota, Geothermal Willow River Geothermal is the top geothermal system contractor in Mahtowa, Minnesota. We'll help you understand all the benefits of geothermal heating and cooling. We’ll see to it that your geothermal unit is properly installed, too. And when it comes time for service? Nobody in Mahtowa can beat our service! Contact Willow River Geothermal today. Like a little up-front look at the savings a geothermal heating and cooling system can give you? Use our simple Geothermal Savings Calculator.