Really? Maybe not, even some advocates concede.
"You could probably pack four people in a car, eat at restaurants, stay in hotels, and I imagine it's about the same cost," said Chuck Woodbury, editor of RVTravel.com, a consumer website offering tips and tricks for RVers.
But consider the intangibles.
"The real advantage of the RV is that the family's together, and you can cook and eat healthy meals," Woodbury said. "There's something about being in a little house that's very appealing. Sitting around a campfire at night is a lot more fun than sitting around a hotel room and watching TV."
Pauline Frommer, creator of the Pauline Frommer's Travel Guides series for budget travelers, said she was won over by her first-ever family RV trip last year. (And, yes, "we probably spent exactly what we would have spent if we went on a car road trip," she added.)
I priced a hypothetical one-week vacation trip for a family of four from Los Angeles to South Lake Tahoe and back in July by rented RV versus going in the family car and staying at a hotel. Excluding food, the cost was about the same. But because it's typically cheaper to make your own meals than to eat out, the RV won by a nose. (I priced a 25-foot Class C RV rental with a KOA campground stay and used a standard AAA calculator for driving costs of a medium sedan, with some tweaks.)
But why spend more than you need to? With that in mind, I gleaned tips from Woodbury and Frommer on how to save.
Rent the right size. Many people overestimate what they need.
Frommer's family of four rented a 30-foot RV to tour the West. But in Sedona, Ariz., she said, "we realized we couldn't drive it to a trail head. It was too big to park anywhere. So we turned out having to rent another car."
Next time, she said, they'll rent a smaller unit or even a pop-up camping trailer, which Woodbury said often rents for a fourth of what a regular RV costs.
Scout out free or low-cost parking: On my hypothetical trip, it cost $69 a night to park my RV with full hookups.
"You picked the high season and a very popular spot," which boosted the price, Woodbury said.
Many private and national forest campgrounds charge less than $25 a night, he said. Cheaper spots don't come with hookups or may just have water and electric. So consider doing without for a night or two, Woodbury said; rely more on battery power and siphon waste into a dump station.
You can park free on some public lands, he added, and many Wal-Marts will let you pull into their lots and spend the night — not exactly a nature experience, but OK in a pinch. For tips on cheap parking places, check out websites such as FreeCampgrounds.com.
Don't write off private campgrounds, such as KOA, which may cost more but provide a resort-like experience.
"KOA is great for kids," Woodbury said. "They're in heaven. Many KOAs have swimming pools, game rooms, pancake breakfasts, movies at night and ice cream socials. It's safe. There's a store for supplies."
Vacation off-season. By avoiding summer, the peak time for RV rentals in most places, you'll pay less. Cruise America, which claims to be North America's largest RV rental company, was recently giving 25% off rentals between Sept. 10 and Dec. 15.
Grab a one-way special. Rental companies sometimes need to move their inventory around, and if you help them, you can get "incredible deals," Woodbury said.
Cruise America, for instance, was recently offering one-way autumn rentals from Carson, Calif., to Phoenix for $24 a night, with 1,000 free miles and no dropoff fee. By comparison, when I priced the 25-foot RV for my hypothetical trip in July, the company quoted $169 a night, plus 32 cents a mile.