“Across all of our businesses, we are actively working to support the energy transition. In addition to the many opportunities at Centuri, Southwest Gas is advancing its sustainability initiatives and ongoing low-carbon projects, while MountainWest has numerous attractive opportunities with renewable natural gas, responsibly sourced natural gas, hydrogen and CO2 transportation,” said Mr. Hester.
During the fourth quarter of 2021, consolidated net income was $69.9 million, or $1.15 per diluted share, and adjusted consolidated net income was $98 million, or $1.61 per diluted share, compared to $103.5 million, or $1.82 per diluted share, for the fourth quarter of 2020. Quarterly results for 2021 included a $3 million, or $0.05 per share, increase in income from COLI investments, while the prior-year quarter included COLI-related income of $8.2 million, or $0.14 per share.
Natural Gas Distribution Segment Results
Full Year 2021
Southwest Gas increased its operating margin $83 million year-over-year, including $13 million from continued customer growth, as 37,000 first-time meter sets were added in 2021, and $61 million of incremental operating margin from combined rate relief in 2021. Regulatory account recoveries benefitted operating margin in both periods, in addition to margin from customers outside of decoupling mechanisms. Southwest Gas also benefitted from increased collection of late fees due to the lifting of the pandemic-period moratorium on these fees.
Operations and maintenance expense increased $32 million, or 8%, year-over-year primarily due to higher legal-claim related costs including a $5 million legal reserve, higher levels of service-related pension costs ($6.9 million), collective increases in customer service-related and information technology costs, including staffing, training, and stabilization costs associated with a new customer information system implemented in May 2021 ($8.7 million) to improve the customer experience, expenditures for pipeline damage prevention programs ($5.5 million) to support our growing infrastructure and customer base, and higher reserves for customer accounts deemed uncollectible.
Depreciation and amortization expense increased $18 million, or 8%, year-over-year primarily due to a $559 million, or 7%, increase in average gas plant in service in 2021. The increase in gas plant was attributable to pipeline capacity reinforcement work, franchise requirements, scheduled pipe replacement activities, and new infrastructure, as well as a new customer information system noted above. Amortization related to regulatory account recoveries increased $3.5 million year-over-year, which is offset by an increase in operating margin noted above. Taxes other than income taxes increased $16.9 million, or 27%, year-over-year primarily due to an increase in property taxes in Arizona, and to a lesser extent, in Southwest Gas’ California and Nevada jurisdictions.
Other income increased $2 million year-over-year. Non-service-related components of employee pension and postretirement benefit cost in this category decreased $6 million year-over-year. The current year also includes a $1.1 million increase in interest income compared to the prior year. Offsetting these impacts were reductions ($4.7 million) in the equity portion of the allowance for funds used during construction (“AFUDC”) due to the impact short-term borrowings have on AFUDC. Both years experienced returns on Company Owned Life Insurance (“COLI”) policies that were significantly higher than expected ($8.8 million in 2021 and $9.2 million in 2020).
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