Transmission Expansion Investment Evaluation Considering the Impact of Behind-the-Meter Generation

Behind-the-meter (BTM) generation and energy communities reduce the demand that transmission networks must carry, yet expansion planning still treats that demand as given. This paper examines transmission investment when demand growth, including new large loads such as data centres, is supplied behind the meter instead of being connected directly to the transmission grid. BTM self-supply is represented as a virtual transmission resource, a nodal reduction of net demand, in static and multi-period mixed-integer linear expansion models with a DC network representation, and a BTM Index (BTMI), which covers individual self-generation and energy communities, ranks the nodes where BTM deployment should be promoted. Applied to the Garver system and the Colombian 500 kV backbone, the methodology shows that the required transmission capital expenditure decreases as BTM penetration grows, and that part of it is postponed: in Colombia a 5 % penetration removes 30 % of the base plan, a 30 % penetration removes 88 %, and final penetrations of 10 % and 20 % reduce its present value by 27.5 % and 53.7 %. The reduction occurs in steps, depends on where the resource is located and is bounded by the connection of new load. Future assessments should add the N-1 criterion and both the night-time peak and the daytime high-solar condition.