There has been a lot of progress in recent years. In 2002, when the Human Rights Campaign compiled its first Corporate Equality Index tracking company policies of concern to the LGBT community, only 13 large U.S. employers earned a perfect score — Pacific Gas and Electric Company was one of them. That figure has now climbed to a record 366, out of the 781 companies surveyed.
But the push for equality in the workplace includes plenty of unfinished business. For example, just one-third of the Fortune 500 earned a "perfect" 100-point rating.
Read MoreOpinion: Gay marriage's big benefit is Social Security
While it's hard to believe, there are still places in the U.S. where someone can be fired for being "out" at work. As business leaders, we have a responsibility to end this kind of discrimination. Even where there are legal protections in place, many people still don't feel safe to be who they are at work. They worry they will be thought less of, won't fit in, or will be passed up for promotion.
That's not only wrong, it's bad for business. From a human- resources perspective, employee engagement is critical, as it indicates how committed employees are to the success of their company. So it should come as no surprise that, when employees feel they need to cover or hide who they are at work, it undermines their engagement and overall job satisfaction.
Companies also compete for talent. In the San Francisco Bay Area, where we're headquartered, the competition can be fierce. We find that millennials in particular, whether LGBT or not, want to work for forward-looking companies with progressive policies. And equality is a threshold issue for them.
At PG&E, diversity and inclusion have long been top priorities. It starts with policies and practices. For years, our company has provided full benefits for domestic partners. We were the first utility in to oppose Proposition 8, a 2008 California ballot initiative aimed at precluding same-sex marriage. And we were among the first major companies to include LGBT-owned businesses in our supplier-diversity program.
Read MoreCorporate America is marching with gay pride
But it's also about shaping corporate culture. That takes time and it takes leadership. PG&E is home to one of the nation's oldest LGBT employee-resource groups, which will celebrate its 30th anniversary this coming year. Recently, our executive leaders have been part of the "I'm an Ally" campaign to support LGBT inclusion. And on Sunday, many of them marched side-by-side with employees in this year's San Francisco Pride Parade. That's powerful.
We do these things because creating a culture of inclusion makes us a better company. Because we know we're building relationships that produce economic and social value in our communities. Because we believe companies like PG&E have a responsibility to lead by example.
We cannot afford to let this historic moment lull us into complacency. It would be easy for Corporate America to assume the job is done. It isn't. There is much more work to do to ensure everyone feels safe being their whole self in the work place.
Commentary by Kent Harvey, chief financial officer at PG&E. He was named Outstanding Corporate Leader of the Year by the National Gay and Lesbian Chamber of Commerce in 2015.