As top leaders overseeing the Texas power grid released an outlook for this winter, they highlighted a looming problem.

Grid leaders are pretty optimistic that because of major changes since the big statewide freeze almost two years ago, the state is more prepared than ever for winter.

But that optimism came with a caveat.

“We fully expect to keep the lights on like we have this winter, like we have in the past - but it's getting harder,” says Peter Lake, chairman of the Public Utility Commission of Texas.

He spoke Tuesday afternoon alongside Pablo Vegas, the new CEO of ERCOT.

They explained the winter outlook report shows for most scenarios, we’ll have enough power. But there is one extreme weather scenario - with a low probability of happening - that the grid could not handle.

Vegas says it points out a big problem with supply and demand.

“Texas is adding a city the size of Corpus Christi every single year in population. And the associated economic growth that comes with that is driving increased usage on the grid,” Vegas says.

So clearly, demand is way up. But Vegas says supply is pretty flat: new power generation just isn’t being built fast enough. But he says the grid is slowly adding battery storage as that technology improves.

Lake noted in the past 18 months, Texas has avoided emergency conditions or blackouts eight times, including during the record heat this summer.