The US used over 3.6 million gigawatts hours of energy in 2020. If you round down, and assume no increase in the last 4 years, that's over 9800 per day. 30 is a drop in the bucket. We have combined cycle natural gas plants, along with other green options to pick up for dips in production exactly like this.
A better question is how much energy we gain from solar if losing it for a couple hours once a decade or so is such a big deal.
He didn't write GWH, he just said GW. For all we know, assuming this number relates to reality at all, that's just smear across the whole eclipse and no single watt was lost for more than a few minutes.
If we lost "30GW", I'd bet we lost barely one GWH.
I was in the penumbra, and around here I would say the entire event took an hour and a half, from "any of the sun at all is covered" to "none of the sun at all is covered." I'm sure our local solar panels did dip in output, probably to the point of producing no useful power for several minutes as it got noticeably darker.