Capital Program Planning for South Dakota Gas Utilities

by | Oct 21, 2026

South Dakota · Natural Gas Utilities

A small customer base, a cold-climate system, and a decade of rate cases. Your capital plan carries all three.

South Dakota's roughly 241,000 gas customers are spread thin across a winter-peaking territory served by three investor-owned utilities and a handful of municipal systems. Integrity work, renewable-gas interconnections, and volatile winter supply all compete for the same dollars — recovered one rate case at a time. Invizion helps gas utilities re-sequence a capital portfolio in a click, and defend every decision.

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The bottom line: South Dakota's ~241,000 gas customers carry a cold-climate system with no infrastructure-replacement surcharge, so capital is recovered one rate case at a time. The utilities that hold rates steady will be the ones whose capital plans can re-sequence as fast as a winter shock or a rate outcome lands.
241,1971
Natural gas customers across South Dakota in 2024, up from 232,622 in 2022.
+123%2
Jump in South Dakota's citygate gas price in 2021 as the February cold snap hit — from $3.33 to $7.43 per Mcf.
33
Investor-owned gas utilities before the SD PUC with rate increases in consecutive years — MidAmerican, Montana-Dakota, and NorthWestern.
$9.322
South Dakota residential gas price per Mcf in 2024 — still roughly 31% above the 2020 level even after the spike eased.

The South Dakota Landscape

Four forces are moving your project list at once

South Dakota's gas sector is small, but the pressures on it are not simpler for being smaller — a thin customer base has to absorb the same integrity, supply, and transition costs as everyone else.

Integrity & Safety

Aging main, spread across a cold, empty map

Every South Dakota gas distribution operator must run a federally mandated Distribution Integrity Management Program — the risk-based leak-management, monitoring, and accelerated-repair regime under 49 CFR Part 192, Subpart P.4

Surveying, upgrading, and replacing steel and plastic main across a sparsely populated, winter-stressed territory is continuous work, and it sits inside recent rate cases — Montana-Dakota Utilities' 2023 South Dakota gas case (NG23-014)5 and NorthWestern Energy's 2024 case (NG24-005)6 — with the cost spread over a base of only a few hundred thousand customers.1

Decarbonization Pressure

No gas ban — but RNG and thinning throughput

South Dakota has no “future of gas” docket or building-electrification mandate, so the near-term pressure is muted. It still reaches the capital plan through renewable natural gas: NorthWestern has signed a string of RNG interconnection and purchase contracts with the state's ethanol and dairy producers — POET Biorefining and others in 2024,7 and Brightmark and POET projects as far back as 2021.8

Meanwhile residential gas deliveries slipped from about 14.6 million Mcf in 2022 to 12.3 million in 2024 even as customer counts rose91 — the early signature of efficiency and milder winters thinning throughput per customer, the dynamic that reshapes long-horizon plans.

Supply & Price Volatility

End of the pipe, exposed to the market

South Dakota sits at the end of long interstate pipelines — NorthWestern's supply moves on Northern Natural Gas3 — and every therm is bought on a volatile continental market and passed through via the purchased-gas adjustment. The February 2021 cold snap made the exposure vivid: the state's citygate price more than doubled year over year, from $3.33 to $7.43 per Mcf,2 and residential prices climbed to a $10.99 peak in 2022 before easing.2

With winters that regularly demand design-day peaking, reliability rests on firm supply, storage, and capacity contracts. Montana-Dakota's parent runs a regulated transmission and underground-storage system with capacity of about 2.6 Bcf per day that anchors part of the region's supply.10

Capital Recovery & Regulatory

No rider — recovery is one rate case at a time

The tension is affordability against necessary investment, and it plays out case by case. Three investor-owned gas utilities have been before the South Dakota PUC in consecutive years — MidAmerican Energy's 2022 gas case (NG22-005),11 Montana-Dakota's 2023 case (NG23-014),5 and NorthWestern's 2024 case (NG24-005).6

South Dakota has no automatic infrastructure-replacement surcharge of the ISRS/DSIC/GSEP kind used in many states; recovery runs through periodic base-rate cases plus the purchased-gas adjustment that passes commodity cost straight through.3 That means the timing and sequencing of capital projects directly drives when, and how much, rates move.

Who Delivers South Dakota's Gas

Three investor-owned LDCs and a set of municipal systems

South Dakota's gas is delivered by three PUC-regulated investor-owned utilities dividing the state geographically, plus several city-owned systems and an intrastate pipeline. The pressures are shared; the accountability path differs.

Investor-owned utilities

Rates & capital recovery regulated by the SD PUC

MidAmerican Energy Natural gas to Sioux Falls — the state's largest gas market3
Montana-Dakota Utilities (MDU) 435,350 gas/electric customers in 273 communities across MT, ND, SD, WY12
NorthWestern Energy Gas & electric across eastern SD; part of 850,300 customers in MT, SD & NE13

Together these three carry the vast majority of South Dakota's ~241,000 gas customers.1

Municipal systems & intrastate pipeline

City-owned gas utilities and an intrastate carrier

Watertown Municipal Utilities City-owned gas department3
Crooks Municipal Gas City-owned gas system3
Garretson Natural Gas City-owned gas system3
Humboldt Municipal Gas City-owned gas system3
South Dakota Intrastate Pipeline Co. Intrastate gas transportation3

Municipal systems set rates through their city councils rather than the PUC, but face the same integrity and supply-cost pressures on a smaller base.

Rate-Setting & Oversight

Every capital dollar has to be defensible

With no automatic infrastructure rider, South Dakota gas utilities make their case in full base-rate proceedings — where the question is always why this project, why now, why at this cost.

  • South Dakota Public Utilities Commission (PUC) regulates the rates and capital recovery of the investor-owned gas utilities — MidAmerican, Montana-Dakota, and NorthWestern — plus the intrastate pipeline.3
  • MidAmerican Energy, 2022 (NG22-005) — application to increase South Dakota natural gas rates, opened May 2022 and closed March 2023.11
  • Montana-Dakota Utilities, 2023 (NG23-014) — application to increase South Dakota natural gas rates, settled and closed September 2024 with a customer refund on the interim rates.5
  • NorthWestern Energy, 2024 (NG24-005) — application to increase South Dakota natural gas rates, filed June 2024 and settled by December 2024.6
  • Purchased-gas adjustment passes commodity cost through to customers between rate cases — the mechanism that absorbed the 2021 winter spike rather than a capital rider.3

How The Capital Gets Recovered

No surcharge shortcut — the plan is the funding case

South Dakota gives gas utilities fewer automatic recovery tools than surcharge states, so what earns a return depends on what lands in the next rate case — and the numbers behind those plans are large relative to the customer base.

  • No ISRS / DSIC / GSEP rider. South Dakota gas utilities recover capital through periodic base-rate cases and pass fuel cost through the purchased-gas adjustment — there is no standalone infrastructure-replacement surcharge.3
  • MDU Resources ~$3.1B capital forecast. Montana-Dakota's parent carries a roughly $3.1 billion capital program, with a proposed Bakken East pipeline project estimated at an additional $2.7–$3.2 billion.14
  • Rate-case revenue funds system work. Montana-Dakota's 2023 gas settlement5 and NorthWestern's 2024 settlement6 both fund continued South Dakota system investment.
  • RNG interconnections add contract-backed capital. A dozen-plus NorthWestern renewable-natural-gas agreements with ethanol and dairy producers since 2021 bring a new capital and revenue stream tied to specific projects.78

Where Invizion Fits

Turn South Dakota's gas-system decisions into a defensible capital plan

Invizion is scenario-based capital portfolio optimization built for utilities. When a replacement mandate accelerates, throughput forecasts shift, or a decarbonization ruling lands, you don't re-plan by hand for weeks — you model it and decide with a record to stand behind.

1

Model the “what-if” before it's forced on you

A faster main-replacement schedule, a gas-line-extension ban, an RNG mandate — build the scenario and see the impact on the whole portfolio, side by side with today's plan.

2

Re-sequence 500 projects in a click

When priorities move, Invizion re-orders the portfolio automatically — accelerating, stretching, or deferring projects against the constraints you set, not weeks of spreadsheet surgery.

3

Give regulators or your board a defensible record

Every prioritization and trade-off is captured. When you're asked “why this project, why now,” the answer is documented — not reconstructed after the fact.

South Dakota Gas, In Brief

Questions South Dakota gas leaders are asking

Short, sourced answers — the same facts we dig into with utilities looking at their capital programs.

How many natural gas customers does South Dakota have?
About 241,197 in 2024 — roughly 212,508 residential, 28,125 commercial, and 564 industrial — up from 232,622 in 2022.1
Which utilities provide natural gas in South Dakota?
Three investor-owned utilities divide the state — MidAmerican Energy (Sioux Falls), Montana-Dakota Utilities, and NorthWestern Energy (eastern SD) — alongside municipal systems such as Watertown, Crooks, Garretson, and Humboldt and an intrastate pipeline, all overseen by the SD PUC.3
How did the February 2021 cold snap affect South Dakota gas prices?
The state's citygate price more than doubled from $3.33 per Mcf in 2020 to $7.43 in 2021, and residential prices climbed to a $10.99 peak in 2022 before easing to $9.32 in 2024. Those commodity costs flow to customers through the purchased-gas adjustment.2
Does South Dakota have a gas infrastructure-replacement surcharge?
No. Unlike ISRS or DSIC states, South Dakota has no standalone capital rider; utilities recover investment in full base-rate cases — three of which (MidAmerican, Montana-Dakota, NorthWestern) ran in consecutive years from 2022 to 2024.1156
Is South Dakota restricting natural gas use?
There is no “future of gas” docket or gas ban. The decarbonization signal shows up mainly through renewable-natural-gas contracts with ethanol and dairy producers and a slow decline in residential throughput per customer.79
How does Invizion help South Dakota gas utilities plan capital?
Invizion is scenario-based capital portfolio optimization for utilities. With no surcharge to smooth recovery, timing is everything in South Dakota — Invizion lets you model how a rate-case outcome, a winter cost shock, an integrity finding, or a new RNG interconnection reshuffles your whole project list, re-sequence the portfolio automatically, and keep a defensible record of every decision for the PUC or your board.

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About the Author

GB

Guy Barlow

President, Invizion

Guy Barlow leads Invizion, a capital lifecycle management platform for water and wastewater utilities. He has spent two decades at the intersection of utility capital programs, funding, and analytics, helping utilities make faster, more defensible capital decisions.

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This briefing was last reviewed September 2026.

Sources

  1. U.S. Energy Information Administration — Number of Natural Gas Consumers, South Dakota (residential 212,508; total 241,197 in 2024). www.eia.gov
  2. U.S. Energy Information Administration — Natural Gas Prices, South Dakota (citygate $3.33 in 2020, $7.43 in 2021; residential $10.99 in 2022, $9.32 in 2024). www.eia.gov
  3. South Dakota Public Utilities Commission — Natural Gas: regulated utilities (MidAmerican, Montana-Dakota, NorthWestern), municipal systems, and dockets. puc.sd.gov
  4. eCFR — 49 CFR Part 192, Subpart P, Gas Distribution Pipeline Integrity Management (DIMP). www.ecfr.gov
  5. South Dakota PUC — Docket NG23-014, Montana-Dakota Utilities application to increase natural gas rates (settled/closed 09/2024). puc.sd.gov
  6. South Dakota PUC — Docket NG24-005, NorthWestern Energy application to increase natural gas rates (filed 06/2024, closed 12/2024). puc.sd.gov
  7. South Dakota PUC — 2024 Natural Gas Dockets, including NorthWestern RNG/POET Biorefining contract approvals. puc.sd.gov
  8. South Dakota PUC — 2021 Natural Gas Dockets, including NorthWestern Brightmark and POET RNG contract approvals. puc.sd.gov
  9. U.S. Energy Information Administration — Natural Gas Consumption by End Use, South Dakota (residential deliveries 14,579 MMcf in 2022 vs 12,272 MMcf in 2024; total ~95 Bcf). www.eia.gov
  10. MDU Resources Group — more than 1.2 million utility customers across eight states; regulated pipeline capacity ~2.6 Bcf/day plus underground storage. www.mdu.com
  11. South Dakota PUC — Docket NG22-005, MidAmerican Energy application to increase natural gas rates (filed 05/2022, closed 03/2023). puc.sd.gov
  12. Montana-Dakota Utilities Co. — more than 435,350 customers in 273 communities across North Dakota, South Dakota, Montana, and Wyoming. www.montana-dakota.com
  13. NorthWestern Energy — 850,300 customers across Montana, South Dakota, and Nebraska; gas and electric service in eastern South Dakota. www.northwesternenergy.com
  14. StockTitan — MDU Resources ~$3.1 billion capital forecast; proposed Bakken East pipeline estimated $2.7–$3.2 billion (2026). www.stocktitan.net