Before David begins, I'd like to mention that a replay of this call will be available through 6 p.m., Central Time, Thursday, August 9, 2012. To access the replay, please call (855) 859-2056 or (404) 537-3406 and enter the conference ID number 91655009. You can also listen to on online replay of the call through the website that I just mentioned. We will archive the call on CenterPoint Energy's website for at least one year.
And with that, I will now turn the call over to David.
David M. McClanahan
Thank you, Carla. Good morning, ladies and gentlemen. Thank you for joining us today, and thank you for your interest in CenterPoint Energy. This quarter was a good one for the company. We had a solid quarter from both a financial and operating standpoint. This morning, we reported net income of $126 million or $0.29 per diluted share. This compares to net income of $119 million or $0.28 per diluted share for the same quarter of 2011.
Operating income for the second quarter was $302 million compared to $303 million last year. Houston Electric had a solid quarter, despite milder weather, compared to 2011. We reported operating income of $153 million, which was the same as the second quarter of 2011. Operating income benefited from the growth of more than 43,000 customers since the second quarter of last year. This represents a growth rate of 2%, which we believe will continue for the remainder of the year.
We also benefited from the ongoing recognition of deferred equity returns associated with the company's recovery of true-up proceeds, and an increase in miscellaneous revenues, primarily from grants of right-of-way easements. Offsetting these benefit was a $15 million impact from the rate changes implemented in September 2011, and higher net transmission cost.
In May, Houston Electric substantially completed the deployment of our advanced metering system, having installed approximately 2.2 million smart meters. We completed this $660 million project, on time and on budget, and I'm very proud of the many employees who contributed to the success of this deployment.