Jayshree Desai
Chief Financial Officer at Quanta Services
Thanks, Duke, and good morning, everyone. Today, we announced record third quarter revenues of $5.6 billion. Net income attributable to common stock was $273 million or $1.83 per diluted share and adjusted diluted earnings per share was a record $2.24. Our third quarter electric power revenues were $2.5 billion, and operating income margins were 11.9% as a result of the exceptional performance by our base business activities and telecom operations. Renewable Energy Infrastructure segment revenues for third quarter '23 was $1.7 billion with operating income margins of 8.7%. The revenue strength in the quarter reflects continued momentum behind renewable energy infrastructure, the quality of our customers and our comprehensive solutions-based approach to the energy transition. Segment margins improved sequentially as construction activities accelerated across our portfolio of projects.
However, they were pressured somewhat by lower-than-expected contingency releases on more mature projects that progressed during the quarter. It's also worth noting that profit associated with revenues from early-stage work is generally recognized at a lower margin as risk contingencies are included in the cost to complete. During periods of high growth and new project starts, this margin dynamic can be exacerbated, which is influencing 2023 segment margins as year-to-date renewable revenues have grown roughly 50% from 2022. Underground Utility and Infrastructure segment revenues were $1.4 billion for the quarter, and operating income margins were 8.9%, driven by high volumes, solid execution and better fixed cost absorption on increased revenues. For additional commentary comparing third quarter '23 to third quarter '22, please refer to the slides accompanying this call, At September 30, 2023, total backlog was a record $30.1 billion, an increase of $2.9 billion compared to June 30, with growth coming from both large project awards and our base business activities.
Our 12-month backlog is also at a record level of $17 billion, approximately $1.4 billion higher than June 30. For the third quarter of 2023, we had free cash flow of $280 million. DSO measured 79 days for the third quarter, aided by several billing arrangements associated with certain awards during the quarter. Regarding the Canadian renewable transmission project we've discussed in prior calls, the contract asset balance grew during the quarter as we progressed closer to completion. We continue to have favorable discussions with the customer regarding significant portions of the balance representing approximately seven days of DSO as of September 30, and we remain confident in our position. As of September 30, 2023, we had total liquidity of approximately $2 billion and a debt-to-EBITDA ratio of 2.2 times as calculated under our credit agreement.
During the quarter, we made a small acquisition that will primarily report through our electric segment and as we announced in today's release, earlier this week, we closed on the strategic acquisition of Pennsylvania Transformer to help address a critical supply chain constraint for our utility, renewable and industrial customers. While we always measure capital deployment against the return opportunities presented by stock repurchases, we continue to see an active pipeline of strategic opportunities that we believe can be executed at accretive valuation and have the ability to drive significant stockholder value. Turning to our guidance. We performed well through the first nine months of the year, and demand for our portfolio of solutions remains robust. As a result, we are raising our consolidated revenue expectations for the year to range between $20.1 billion and $20.4 billion.
From a segment perspective, last quarter, we expected electric volumes to ramp in the fourth quarter. However, as it stands today, we now see revenues in the fourth quarter comparable to the third quarter. Part of the fourth quarter reduction reflects the transferability of resources between the electric and renewable segment as renewable revenues continue to expand and encompass both interconnection and generation projects with interconnection work being performed by crews that would otherwise be captured in the electric segment. Additionally, we are seeing pockets of inefficiencies due to supply chain dynamics as well as timing of capital deployment in certain regions shifting into 2024. This variability is a periodic disruption to an otherwise growing demand for our electric solutions, as evidenced by our backlog growth from June 30 levels.
Accordingly, we now see electric segment revenues for the year between $9.6 billion and $9.7 billion and full year margins for the segment ranging between 10.4% and 10.6% as we continue to build crews and carry costs necessary to execute on the anticipated growth in multiyear utility programs. Of note, we are forecasting storm revenues for the year of around $300 million, roughly 3% of segment revenues for the year, the lowest level since 2019. Regarding our renewables segment, given the performance of the third quarter and continued backlog growth, we are raising our full year revenue expectations to range between $5.8 billion and $5.9 billion. Because of the previously described margin dynamics as well as continued investments in labor, training and equipment required to address the segment's building backlog, we now expect margins for the segment to be around 8% for the year.
After another strong quarter, we now expect revenue from our underground segment to range between $4.7 billion and $4.8 billion, a $300 million increase at the midpoint. From a margin perspective, we expect full year margins for the segment to range between 7.6% and 7.8%, an improved outlook and above the previous high end of our range. Not included in our expectations are contributions from Pennsylvania Transformer, which will be captured in both our electric and renewable segments. We are working through purchase price allocation and accounting considerations and aren't prepared to give any definitive guidance, but given the size of the business today, we don't expect the contribution to be material to our quarterly results. In the aggregate, we expect revenues for the year to be almost 20% higher than 2022, and we've increased our expectations for full year adjusted EBITDA to ranging $1.91 billion and $1.95 billion.
For full year adjusted diluted earnings per share attributable to common stock, we've now narrowed our prior range, maintained our previous midpoint and now expect between $7 and $7.20. With regard to free cash flow, we continue to expect between $800 million and $1 billion. We slightly modified other aspects of our guidance, the details of which are included in our outlook summary, which can found in the Financial Information section of our IR website at quantaservices.com. Our growing backlog and favorable multiyear outlook continues to give us confidence in our ability to achieve the multiyear targets we laid out in our April 2022 Investor Day. Additionally, we believe the acquisition of Pennsylvania Transformer further cements our ability to provide differentiating solutions to our core customers and elevates the critical role we play in the North American energy transition. We are uniquely positioned in the markets we serve and believe we have the opportunity to continue improving our return on invested capital and generating significant stockholder value through organic growth and strategic capital deployment.
I'll now turn it back to the operator for Q&A. Operator?
