Tent Camping with a CPAP?

One of my loved ones now needs a CPAP. We are tent campers. Not ready to explore cabins or RVs. I know electric sites exist but have never used one. Can someone explain to me how or whether household items, like a CPAP, can be run at an electric site? Has anyone tent camped with a CPAP? Trying to avoid a $3K battery if we can.