I'm in Texas & our SP's charge a daily PP use fee (over 13) even if you are camping. I buy a SP Pass every year for $70. I'm too lazy to look it up but I THINK any person can buy one -- TX resident or not. That exempts anyone in your party from the daily use fee.
BUT ...... With that SP Pass you also get 4 50% off nights loaded onto your card to use on any visit of 2 nights or more (1 per visit). So potentially you 'get back' at LEAST $50 of that $70 in reduced fees. So it's an awesome deal.
That said, we've also camped in NM, FL, & AR. Their campground charges are researched fully as I check out IF a SP Pass is available to non-residents and IF I purchased one would it pay for itself during my trip.
At any rate ALL the SPs I've had the pleasure to stay in we're great. I LOVE supporting the SP system. Although, being from Texas where sites come with JUST water, W/E, or W/E/S, I WOULD be confused to find an electric-only site. We just don't have those except maybe in tent-only areas.