From the Evergreen page of the Eau Claire Energy Cooperative:

Evergreen is a voluntary renewable energy (green power) program available to your home, farm, or business through Eau Claire Energy Cooperative, a member-cooperative of the Dairyland Power system. Evergreen is for those who want to do more to support renewable energy generation.

This is how it works:
1. You choose one of the Evergreen Levels listed below.
2. For each block (100 kWh) you will be purchasing that amount of energy from a renewable energy source.
3. Your energy bill will be charged the additional cost (see chart below) to help offset the cost it takes to support renewable energy.
4. A one year subscription is required, but after that you can cancel at any time.