Xcel Energy-owned subsidiary Northern States Power Company (NSP) has become the latest utility to seek regulatory approval of a tariff aimed at customers wanting to connect new large loads to the electricity grid.

As of this month, the utility has received a cumulative 2.9 GW of large load requests, with its parent company having received around 30 GW of requests in the eight states in which it operates.

Despite being open to all industries, NSP noted that new customers looking to take service on the new tariff – named the Very Large General Time of Day Service tariff – would be “almost exclusively data centers.”

NSP has asked the Public Service Commission of Wisconsin (PSCW) to approve the new tariff by February 1, 2027.

Applicable to loads exceeding 100 MW, no minimal load factor

Although the utility already has a mandatory tariff for new demand customers, this is only required for projects with a load capacity exceeding 200kV – a size several degrees of magnitude smaller than most new data center projects.

With this in mind, NSP will make its new tariff mandatory to any demand projects exceeding 100 MW. The utility said this figure was “benchmarked across the industry, designed to ensure no existing customer was impacted, and evaluated relative to the financial risks posed by customer size.”

Unlike other similar large load tariffs enacted across the US, NSP’s is based upon interconnection capacity (as opposed to billed demand) and doesn’t feature minimum load factor requirements.

Tariff requirements and obligations

In terms of up-front costs, large load customers will be required to cover 100% of transmission and network upgrade costs prior to project energization.

Once operational, customers will then be responsible for five different pricing components which aim to cover all costs incurred by NSP relating to supporting the new large load. These include energy charges to recover fuel costs and demand charges to recover O&M services.

Customers will be required to supply NSP with an estimated load forecast on January 1st and June 1st of each year for the entirety of the mandatory 15-year contract term. Unless terminated by the customer, this initial 15-year term will be extended by successive five-year periods.

As part of its application with the PSCW, NSP stated that a hypothetical 500 MW load on the new tariff would reduce existing customers rates by up to 2%, whilst also bringing in between USD 490m-630m in the form of taxes and rate relief across the initial 15-year term.

Elsewhere in Wisconsin, NPM reported in May that WEC Energy had received approval from the PSCW of its similar large load tariff, which will also be mandatory for demand projects exceeding 100 MW.

NPM has reported on the introduction of many large load tariffs during the past 18 months, including those introduced by Rappahannock Electric in Virginia, Tri-State G&T who operate across several states in the west of the country and Portland General Electric in Oregon.