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Exhibit 24-A POWER OF ATTORNEY  I, KEVIN G. MOUG, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Chief Financial Officer and Treasurer of Otter Tail Corporation, the Annual Report of Otter Tail
Corporation on Form 10-K for its fiscal year ended December 31, 2004, and any and all amendments to
said Annual Report, and to deliver on my behalf said Annual Report and any and all amendments
thereto, as each thereof is so signed, for filing with the Securities and Exchange Commission
pursuant to the Securities Exchange Act of 1934, as amended. Date: January 31, 2005 /s/ Kevin G. MougKevin G. Moug
 In Presence of: /s/ Gary
Spies  /s/ Charles R. Hoge




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POWER OF ATTORNEY  I, John MacFarlane, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on
Form 10-K for its fiscal year ended December 31, 2004, and any and all amendments to said Annual
Report, and to deliver on my behalf said Annual Report and any and all amendments thereto, as each
thereof is so signed, for filing with the Securities and Exchange Commission pursuant to the
Securities Exchange Act of 1934, as amended. Date: January 31, 2005 /s/ John MacFarlaneJohn MacFarlane
 In Presence of: /s/ Thomas Brown  /s/ Dennis Emmen




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POWER OF ATTORNEY  I, Karen Bohn, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or any
one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Karen BohnKaren Bohn
 In Presence of: /s/ Kenneth L. Nelson  /s/ John MacFarlane




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POWER OF ATTORNEY  I, Thomas Brown, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Thomas BrownThomas Brown
 In Presence of: /s/ John MacFarlane  /s/ Karen M. Bohn




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POWER OF ATTORNEY  I, Dennis Emmen, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or any
one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Dennis EmmenDennis Emmen
 In Presence of: /s/ Nathan Partain  /s/ Arvid R. Liebe




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POWER OF ATTORNEY  I, Arvid Liebe, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or any
one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Arvid R. LiebeArvid Liebe
 In Presence of: /s/ Gary Tygesson  /s/ Lauris Molbert




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POWER OF ATTORNEY  I, Kenneth Nelson, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Kenneth L. NelsonKenneth Nelson
 In Presence of: /s/ Karen Bohn  /s John MacFarlane




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POWER OF ATTORNEY  I, Nathan Partain, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Nathan PartainNathan Partain
 In Presence of: /s/ Arvid R. Liebe  /s/ Gary Tygesson




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POWER OF ATTORNEY  I, Gary Spies, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or any
one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: March 8, 2004 /s/ Gary SpiesGary Spies
 In Presence of: /s/ Charles R. Hoge  /s/ John Erickson




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POWER OF ATTORNEY  I, Robert Spolum, do hereby constitute and appoint JOHN D. ERICKSON and GEORGE A. KOECK, or
any one of them, my Attorney-in-Fact for the purpose of signing, in my name and on my behalf as
Director of Otter Tail Corporation, the Annual Report of Otter Tail Corporation on Form 10-K for
its fiscal year ended December 31, 2004, and any and all amendments to said Annual Report, and to
deliver on my behalf said Annual Report and any and all amendments thereto, as each thereof is so
signed, for filing with the Securities and Exchange Commission pursuant to the Securities Exchange
Act of 1934, as amended. Date: January 31, 2005 /s/ Robert N. SpolumRobert Spolum
 In Presence of: /s/ Kevin Moug  /s/ Gary Spies