The four products you'll be offered
At every US rental counter you'll be pitched four optional coverages: Loss Damage Waiver (LDW, sometimes called Collision Damage Waiver), Supplemental Liability Insurance (SLI), Personal Accident Insurance (PAI), and Personal Effects Coverage (PEC). They are bundled into a single 'Recommended Protection Package' that runs $30–55/day. That bundle typically doubles the cost of an Economy rental.
Loss Damage Waiver — the only one that ever matters
LDW isn't insurance — it's the rental brand agreeing not to charge you for damage to the rental vehicle. If you have a personal auto policy with comprehensive and collision coverage, that policy already covers rentals (call your agent to confirm). If you booked with a credit card that includes rental coverage as a benefit (most travel cards do), you have it for free. The catch: card-based coverage is usually secondary, meaning your auto policy pays first and the card covers the deductible. If you don't own a car or your card explicitly excludes rentals, buying the LDW is reasonable.
Supplemental Liability — almost always skip
Your personal auto policy's liability limits extend to rental vehicles in all 50 states. SLI raises your liability cap to $1M, which is meaningful only if you have substantial assets to protect and a thin personal policy. For most renters, skip.
Personal Accident & Personal Effects — skip
PAI duplicates your health insurance and PIP coverage. PEC duplicates your homeowner/renter policy. Both are pure profit for the rental brand.
What credit cards typically include
Visa Signature, Mastercard World Elite, and most American Express cards include rental coverage as a benefit when you pay for the rental with that card. Rules vary: Amex requires you to enroll in 'Premium Car Rental Protection' for primary coverage ($25 flat fee per rental), while Chase Sapphire and Capital One Venture include primary coverage automatically on most rentals. Read your card benefits guide once and screenshot the relevant page.
When to actually buy LDW at the counter
Three cases: you don't own a car (so no auto policy), your trip is in a country where your auto policy doesn't extend, or you're driving in conditions where damage feels likely (snow, rough roads, unfamiliar mountain passes). Even then, third-party providers like Allianz or RentalCover.com sell standalone coverage at one-third the price of counter LDW.