Open Season MT to Idaho Calendar of Events Posted on NWE OASIS September 30, 2004 (Slide 8 updated 2/28/05)

2 Calendar of Events Summary October 1 – 31, 2004 Phase 1 – Expression of Interest (EOI) NWE evaluation of EOI: through mid November; NWE to announce final dates for Open Season December 1 – 31, 2004 Phase 2: Expected Open Season dates: (Period that Transmission Requests may be placed in the QUEUE) System Impact Studies on Open Season Capacity: at least 60 days following 12/31 depending on complexity 30 day Participant review period before NWE issues Facilities Study Agreements Post December 31, 2004 Phase 3: Facilities Study Process Interested Participants execute Facilities Studies

3 NorthWesterns Open Season Process October 1 – 31, 2004 Phase 1 – Expression of Interest (EOI)Phase 1 – Expression of Interest (EOI) Opportunity for generators/suppliers/load serving entities to come together to help NorthWestern define the market for transmission capacityOpportunity for generators/suppliers/load serving entities to come together to help NorthWestern define the market for transmission capacity NorthWestern will use EOI to determine if sufficient interest to continue with Open SeasonNorthWestern will use EOI to determine if sufficient interest to continue with Open Season

4 Phase 1 – Expression of Interest (EOI) Interested parties to respond with:Interested parties to respond with: Capacity requested – 25 MW blocks Capacity requested – 25 MW blocks Direction of capacity request Direction of capacity request Start date for capacity needs Start date for capacity needs Term of agreement for capacity (minimum term requirement) Term of agreement for capacity (minimum term requirement) NorthWestern Energy EOI forms posted on OASIS NorthWestern Energy EOI forms posted on OASIS

5 Phase Two – Capacity Open Season Preview Period December 1 – 31, 2004 Phase 2 – Open Season PreviewPhase 2 – Open Season Preview NorthWestern evaluates expressions of interest to determine most likely capacity addition(s)NorthWestern evaluates expressions of interest to determine most likely capacity addition(s) Mid-November 2004 – NorthWestern will post on OASIS the start and end dates to accept transmission service requests that will qualify for the open season processMid-November 2004 – NorthWestern will post on OASIS the start and end dates to accept transmission service requests that will qualify for the open season process

6 Open Season Elements Open Season is for Transmission Service Requests with MT-SW (BOBR) as POR or POD ONLY and for NEW (not existing) capacityOpen Season is for Transmission Service Requests with MT-SW (BOBR) as POR or POD ONLY and for NEW (not existing) capacity Same process for making Transmission Service Request (TSR) as described in Section 17 of NorthWesterns Open Access Transmission Tariff with these important modifications:Same process for making Transmission Service Request (TSR) as described in Section 17 of NorthWesterns Open Access Transmission Tariff with these important modifications: 1.Completed Application for Transmission Service will temporarily be considered complete without the deposit of approximately one months transmission service (OATT section 17.3); the deposit will be DELAYED 2.System Impact Study and associated study fee will be waived (NorthWestern will absorb cost of System Impact Studies) As always, date/time stamped OASIS Transmission Service Request will determine customers position in Transmission Service QUEUE

7 Open Season – Current Customers Current transmission customers with completed applications for new capacity requests for transmission service on MT-SW path will be deemed to be part of Open Season (with QUEUE positions already established with reservation on OASIS)Current transmission customers with completed applications for new capacity requests for transmission service on MT-SW path will be deemed to be part of Open Season (with QUEUE positions already established with reservation on OASIS) NorthWestern will work with these current customers on treatment of deposits and study feesNorthWestern will work with these current customers on treatment of deposits and study fees

8 Open Season Elements – System Impact Study Results Upon Open Season capacity request date closing, NorthWestern will require approximately a day period to evaluate total transmission requests and physical options to serve such requestsUpon Open Season capacity request date closing, NorthWestern will require approximately a day period to evaluate total transmission requests and physical options to serve such requests Results of study work will be provided to each Open Season Participant and posted on NorthWesterns OASISResults of study work will be provided to each Open Season Participant and posted on NorthWesterns OASIS Participants will be given 30 days to review results of studies and then will be provided a Facilities Study Agreement by NorthWestern to execute in order to continueParticipants will be given 30 days to review results of studies and then will be provided a Facilities Study Agreement by NorthWestern to execute in order to continue

9 Phase 3 – Facilities Study Facilities Study Agreement must be executed and returned to NorthWestern within 15 business days together with Facilities Study Fee AND Deposit approximating one months Transmission Service (at this point, each Open Season Participant has returned to normal Transmission Service Request Procedures)Facilities Study Agreement must be executed and returned to NorthWestern within 15 business days together with Facilities Study Fee AND Deposit approximating one months Transmission Service (at this point, each Open Season Participant has returned to normal Transmission Service Request Procedures) Failure to comply with above will result in OASIS reservation deemed withdrawnFailure to comply with above will result in OASIS reservation deemed withdrawn