• In the MGP, hourly energy blocks are traded for the next day.
  
• Participants submit offers/bids where they specify the quantity and the minimum/maximum price at which they are willing to sell/purchase. 
  
• The MGP sitting opens at 8 a.m. of the ninth day before the day of delivery and closes at 9 a.m. of the day before the day of delivery. The results of the MGP are made known within 11:30 a.m. of the day before the day of delivery.
  
• Bids/offers are accepted under the economic merit-order criterion and taking into account transmission capacity limits between zones. Therefore, the MGP  iis an auction market and not a continuous-trading market.
  
• All the supply offers and the demand bids pertaining both to pumping units and consuming units belonging to foreign virtual zones that are accepted in the MGP are valued at the marginal clearing price of the zone to which they belong. This price is determined, for each hour, by the intersection of the demand and supply curves and is differentiated from zone to zone when transmission capacity limits are saturated. 
  
• The accepted demand bids pertaining to consuming units belonging to Italian geographical zones are valued at the “Prezzo Unico Nazionale” (PUN – national single price); this price is equal to the average of the prices of geographical zones, weighted for the quantities purchased in these zones.
  
• GME acts as a central counterparty.
  

The Intra-Day Market (MI) allows Market Participants to modify the schedules defined in the MGP by submitting additional supply offers or demand bids. The MI takes place in four sessions: MI1, MI2, MI3 and MI4.

•   The sitting of the MI1 takes place after the closing of the MGP. It opens at 10:30 a.m. of the day before the day of delivery and closes at 12:30 p.m. of the same day. The results of the MI1 are made known within 1:00 p.m. of the day before the day of delivery.
  
• The sitting of the MI2 opens at 10:30 a.m. of the day before the day of delivery and closes at 3:00 p.m. of the same day. The results of the MI2 are made known within 3:30 p.m. of the day before the day of delivery. 
  
• The sitting of the MI3 opens at 4:00 p.m. of the day before the day of delivery and closes at 7:30 a.m. of the day of delivery. The results of the MI3 are made known within 8:00 a.m. of the day of closing of the sitting.
  
• The sitting of the MI4 opens at 4:00 p.m. of the day before the day of delivery and closes at 11:30 a.m. of the day of delivery. The results of the MI4 are made known within 12:00 p.m. of the day of closing of the sitting.
  
• Supply offers and demand bids are selected under the same criterion as the one described for the MGP.
  
• Unlike in the MGP, accepted demand bids are valued at the zonal price. 
  
• GME acts as a central counterparty.
  

The Ancillary Services Market (MSD) is the venue where Terna S.p.A. procures the resources that it requires for managing, operating, monitoring and controlling the power system (relief of intra-zonal congestions, creation of energy reserve, real-time balancing). In the MSD, Terna acts as a central counterparty and accepted bids/offers are valued at the offered price (pay-as-bid).

The MSD consists of a scheduling stage (ex-ante MSD) and of the Balancing Market (MB). The ex-ante MSD and the MB take place in multiple sessions, as specified in the dispatching rules.

The ex-ante MSD consists of three scheduling substages: MSD1, MSD2 and MSD3.  The sitting for bid/offer submission into the ex-ante MSD is a single one. It opens at 3:30 p.m. of the day before the day of delivery and closes at 5:00 p.m. of the day before the day of delivery. The results of the MSD1 are made known within 9:00 p.m. of the day before the day of delivery. GME notifies Market Participants of the individual results of the MSD2 session (as specified in the dispatching rules) concerning the bids/offers accepted by Terna within 10:00 a.m. of the day of delivery. GME notifies Market Participants of the individual results of the MSD3 session (as specified in the dispatching rules) concerning the bids/offers accepted by Terna within 2:00 p.m. of the day of delivery. In the ex-ante MSD, Terna accepts energy demand bids and supply offers in order to relieve residual congestions and to create reserve margins.

The MB takes place in different sessions, during which Terna selects bids/offers in respect of groups of hours of the same day on which the related MB session takes place. At present, the MB consists of 5 sessions. The first session of the MB takes into consideration the valid bid/offers that Participants have submitted iin the previous MSD session. For the other sessions of the MB, all the sittings for bid/offer submission open at 11:00 p.m. of the day before the day of delivery (and anyway not before the results of the previous session of the ex-ante MSD are made known) and close 1 hour and a half before the first hour which may be negotiated in each session. In the MB, Terna accepts energy demand bids and supply offers in order to provide its service of secondary control and to balance energy injections and withdrawals into/from the grid in real time.

For details, refer to the  Vademecum of GME’s Electricity Markets.