Stacked vs. Unstacked Car Insurance

Stacked car insurance lets you combine uninsured motorist (UM) coverage limits across multiple vehicles under the same policy or across multiple policies that list your name. For instance, if you have a $25,000 UM limit on one car and $50,000 on another, stacking gives you up to $75,000 in total coverage if you're injured by an uninsured driver. 

There are two main types of insurance stacking: stacking within one policy and stacking across multiple policies, also known as vertical and horizontal stacking, respectively.

Otherwise known as interpolicy stacking, horizontal stacking lets you combine uninsured motorist (UM) bodily injury coverage from multiple auto insurance policies. Your name must be listed on each policy, and they must be issued by the same insurer.

For example, if you have $35,000 in UM coverage on your own policy and you're also listed on a parent’s policy with $25,000 in coverage, you could stack those for a total of $60,000 in protection against an uninsured driver.

Also known as intrapolicy stacking, this method lets you combine uninsured motorist (UM) bodily injury coverage across multiple vehicles insured under the same policy.

For example, if you have two cars on the same policy and each has $15,000 in UM coverage, stacking them gives you a total of $30,000 in protection if you're hit by an uninsured driver. Vertical stacking only works if you insure more than one vehicle under the same policy, so it’s ideal for multi-car households looking to increase their coverage.

Insurance stacking isn’t available in every state. According to Allstate, 22 states allow vertical and horizontal stacking, 10 states only allow vertical stacking and 18 states prohibit stacking. 

You can review the table below to see which type of stacking is allowed in your state.

Even if your state allows stacking coverage, your insurer may not. Some states also have specific limits in place for stacking, so speak to your provider directly to explore your options for coverage.

Whether stacked insurance is worth the extra cost depends on your situation. It can offer significant benefits for drivers with multiple vehicles, those living in high-risk states or anyone who wants more protection for a small increase in premium. Below are common scenarios where stacking may be a smart move.

Unstacked car insurance limits your uninsured motorist coverage to just one vehicle: the one involved in the accident. You can’t combine coverage across multiple vehicles or policies, even if you own more than one. It’s typically cheaper than stacked insurance but provides less financial protection if an uninsured driver hits you.

Not every state allows you to stack coverage. Below is a list of states that don’t allow stacking at all.

• Alaska
• Arizona
• California
• Connecticut
• Idaho
• Illinois
• Iowa
• Kansas
• Louisiana
• Maine
• Maryland
• Massachusetts
• Michigan
• Minnesota
• Nebraska
• North Dakota
• South Dakota
• Washington

If your state doesn’t allow stacked insurance, you’re not out of options. There are other ways to strengthen your financial protection in case you’re hit by an uninsured or underinsured driver.

Stacked insurance increases uninsured motorist coverage by combining limits across vehicles or policies. It is a valuable option for multi-car owners or if you live in a state with a high number of uninsured drivers. However, it comes with slightly higher premiums. If you’re in a low-risk state or only insure one vehicle, unstacked coverage usually provides adequate protection at a lower price.

The choice between stacked and unstacked insurance depends on your location, coverage needs and budget.

Stacked insurance can help protect you in the event of an accident. We answer some frequently asked questions about insurance stacking.

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