I wish I could give you a definitive answer, but it would be irresponsible to do so in light of the sheer number of different types of auto insurance policies and providers that exist. In other words, I wouldn’t want to make a sweeping statement that leaves you vulnerable due to the specific language and nature of your policy.
In most cases, however, the types of coverage, liability limits and deductibles associated with your policy will extend to rental cars. That means if, for example, you only have liability coverage as part of your current auto insurance plan, you won’t have any collision coverage for physical damage that may occur to a rental car. Likewise, if you have relatively low collision coverage and you end up totaling a rental car, you’ll likely have to cover the difference between your coverage limit and the cash value of the rental.
The best thing to do is call your insurance provider and ask what you’re covered for and what kind of additional rental coverage you’ll need. It’s really worth doing so because they supplemental coverage rental car companies try to sell you can get quite expensive.
With that said, your auto insurance isn’t the only source of potential rental car coverage you likely already have. Most credit card networks (i.e. Visa, Mastercard, American Express and Discover) and credit card issuers (e.g. BofA, Capital One, etc.) automatically provide some form of rental car insurance.
For example, all Visa cards provide a rental car Collision Damage Waiver as long as you pay for the entire rental transaction with your Visa card and decline any coverage options offered by the rental company itself. This protects you for physical damage and/or theft of your rental up to the actual cash value of the vehicle, reasonable towing charges, and loss-of-use charges assessed by the rental company.
MasterCard, American Express and Discover all seem to have similar policies and at the very least provide some sort of rental car coverage. Again, the best thing to do is call your card’s issuer and ask what kind of coverage your particular card gets you, what types of cars it covers (Amex’s standard coverage only applies to standard rentals), and what, if anything, you need to do to benefit.
Finally, for some people it might make sense to simply purchase an add-on to their auto insurance policy that covers them for all non-owned cars. This is called Unlimited Non-Owned Car Coverage (UNOC) and depending on the company, you may be able to get it, cancel it whenever you so choose, and only have to pay a prorated charge.