Do I have to pay self employment tax on income for excess solar power we produce for our residence and get paid for by the power company?

The IRS sent me a letter wanting me to pay self employment tax on the income we receive from the excess power we produce at our residence and Intuit seems to say that I do not pay self employment tax on that income.  Since 2013 I have put that income on "other income" line and have not paid self employment tax as I didn't consider it a business!