Demand

How demand is modeled across SPP

Demand is modeled at the zonal level with hourly resolution. Each settlement zone has a forecast peak that grows over the horizon and an hourly shape drawn from a historical weather year, with large loads layered on top.

Zonal demand forecast

Demand is built per SPP planning area and mapped to the model’s settlement zones; where several planning areas fall within one zone, their load is summed. For each area, a forecast peak level is combined with a historical hourly shape.

The peak level is anchored at two points and interpolated between them:

• Historical anchor: the area’s recent observed peak, derived from metered EIA-930 sub-region data.
• Forward anchor: the area’s ten-year-out peak from SPP’s 2025 Integrated Transmission Plan (ITP), the planning study SPP uses to assess its own system.

Years between the two anchors are interpolated linearly. Beyond the forward anchor, peaks grow at a low single-digit annual rate consistent with SPP’s own long-term peak trajectory. This produces a peak forecast for every zone and forecast year. The hourly shape it is scaled to comes from a historical weather year (see Weather years).

Forecast

Large loads

Large new loads are added on top of the baseload demand forecast: data centers, oil and gas, industrial, manufacturing and commercial demand. They are the largest single driver of demand growth in SPP.

Magnitude and location follow SPP’s 2026 plan by transmission owner

The forecast follows SPP’s 2026 Integrated Transmission Plan (ITP) spot-load additions, which SPP publishes by transmission owner. Each zone ramps from zero in 2026 to its own published level in 2030, 2035 and 2045, linearly in between, and holds flat after 2045. Across the modeled footprint that is 10.2 GW by 2030, 17.8 GW by 2035 and 20.4 GW by 2045.

• One owner, several zones: where a transmission owner serves more than one settlement zone, its total is split across them by where its announced data-center projects sit.
• OG&E: all OG&E large load sits in OKGE (East), because every announced campus is east of the split boundary.

Each sector sits where it can plausibly locate

Sectors are not spread evenly across the zones. Oil and gas load sits only in SPS, which covers the Permian Basin. Data-center load sits in the zones with announced campuses.

SPP publishes its 2026 totals by zone, not by sector, so the sector totals are set by Modo:

• Industrial, manufacturing, commercial, hydrogen and other keep their share of SPP’s 2025 large-load list, the most recent list SPP classifies by sector.
• Oil and gas is SPS’s load, apart from two data-center campuses under construction near Abernathy, Texas.
• Data centers take the remainder, which places most new large load in the zones with announced campuses.

The mix is then fitted year by year so that each zone matches its SPP-published total and each sector matches its target. By 2035, data centers are about 10.0 GW of the 17.8 GW, oil and gas 4.3 GW, industrial and manufacturing 2.7 GW, and commercial, hydrogen and other load 0.8 GW.

Each sector has its own hourly shape

Data-center load follows a month-by-hour profile from the PowerGEM Long-Term Reliability Assessment (LTRA), which is near-flat and peaks at 97% of capacity. Every other sector has its own profile:

Shaping lowers the energy large loads draw while their capacity stays at the SPP-published level. At the published 2035 level, before the SPS deferral below, they draw about 133 TWh.

SPS large loads take grid service five years late

Large loads in SPS run behind the meter for their first five years. SPP’s Tariff Attachment BB terminates a high-impact large load interconnection agreement at five years, when the load takes firm grid service. The model therefore serves the SPS ramp five years later than published, so SPS reaches its full 5.1 GW only in 2040.

The chart shows the large load the grid serves, including that deferral. It is lower than the published totals in the near term: 8.4 GW in 2030 and 14.6 GW in 2035, reaching the full 20.4 GW in 2045.

Weather years

Hourly shapes are tied to a single historical weather year, 2023 in the current forecast, selected from recent years of metered data. For each area, an hourly unit shape is built from EIA-930 sub-region data and scaled to the area’s forecast peak. The same weather year is used across all forecast years, so each year shares one intra-annual pattern scaled to its own peak.

The demand weather year is aligned with the renewable capacity factor weather year, so load and wind and solar output stay weather-consistent. Alternative weather-year shapes can be layered on to support higher and lower demand scenarios.

Load profiles

Assumptions and caveats

• WAUE settlement share: the WAUE zone is largely Basin Electric, whose load splits across SPP, MISO, and WECC, so only the portion settled in SPP is included. 90% of WAUE load is treated as SPP-settled, matching Basin Electric’s SPP share.
• Single weather year: every forecast year reuses one historical weather year’s shape, so it does not capture year-to-year weather variability within a single run.

Data sources