Stacked Vs Unstacked Auto Insurance
Stacked auto insurance allows you to increase your coverage if you get into a car accident and the at-fault driver is uninsured or does not have enough coverage to pay for your medical expenses. Stacking coverage occurs when you have at least two insured vehicles under the same policy or across different policies and you combine each vehicle's coverage to increase your overall limits. This is not possible with unstacked auto insurance — your coverage is restricted to the per-vehicle limits stated in the policy.
Stacked auto insurance has its advantages but may come at an additional cost and is unavailable in 18 states. Learn the differences between stacked vs. unstacked insurance and which is right for you.
What Is Stacked vs. Unstacked Insurance?
Stacked auto insurance refers to an auto policy that allows a driver with at least two insured vehicles to combine each vehicle's uninsured/underinsured motorist bodily injury (UMBI) coverage to increase their total coverage limit.
For example, if two cars under the same policy each have $25,000 in UMBI coverage, then the policyholder can stack their coverage limit to $50,000. Stacking can occur horizontally (stacking within the same policy) or vertically (stacking across different policies) — more on this in the next section.
Unstacked insurance means that coverage across multiple vehicles cannot be stacked to increase your limit. If your policy's UMBI coverage is $25,000 per driver, then you can only be reimbursed up to $25,000 for a single car insurance claim.
Stacked Insurance Claim Example
You and your spouse are listed drivers under the same policy. Each vehicle has uninsured motorist bodily injury coverage limits of $20,000. After an accident in which the other driver is at-fault but has no auto insurance, you suffer an injury and have medical expenses totaling $35,000.
You stack your auto insurance to increase your limits from $20,000 to $40,000 ($20,000 x 2 vehicles). Your medical bills are now fully covered by your auto insurer.
Without stacking, you would have to pay $15,000 out of pocket ($35,000 of medical costs minus $20,000 in coverage).
How Does Unstacked Insurance Work?
In auto insurance, only the bodily injury portion of your uninsured/underinsured motorist (UM/UIM) coverage is stackable. UM/UIM property damage coverage and other types of auto coverages (e.g., collision and comprehensive) cannot be stacked. Stacking UMBI coverage can work horizontally (stacking within the same policy) or vertically (stacking across different policies).
Stacking Within One Car Insurance Policy (Horizontal)
Horizontal stacking occurs when you stack coverage from multiple vehicles under the same auto policy.
Horizontal stacking example: You, your spouse and your child are listed under the same policy with each car carrying $20,000 of UMBI coverage. If any of the drivers in this policy get into an accident, the UMBI limit per person can be increased to $60,000 ($20,000 x 3 vehicles).
Stacking Across Multiple Car Insurance Policies (Vertical)
Horizontal stacking occurs when you stack coverage across multiple car insurance policies that are under your name. In some instances, you may even be able to stack coverage if the separate policies are issued by different car insurance companies.
Vertical stacking example: Your name is listed on two different car insurance policies under the same insurance company. The UMBI coverage limit is $30,000 for the first policy and $20,000 for the second policy. If an uninsured driver hits your vehicle, you can stack your UMBI coverage limit to $50,000 per person ($30,000 + $20,000).
Some auto insurance companies may not allow stacking, even if stacking is available in that state. Auto insurers may write an anti-stacking clause into the policy, which would restrict coverage to a single policy limit.
Stacking is not available in 18 states. In states where stacking is allowed, that state may allow both types of stacking or may only allow vertical stacking, but not horizontal stacking. See our table below for information about stacking availability by state.
States That Allow Stacked Insurance
Below is a list of states where both vertical and horizontal stacking are available. We also distinguish states that accept vertical stacking (across different policies), but not horizontal stacking (within the same policy).
States That Accept Both Types of Stacking
States That Accept Vertical Stacking Only
Keep in mind that not all insurers will allow for stacking. Be sure to confirm with your agent and review your policy for anti-stacking language before signing.
Stacked vs. Unstacked Car Insurance
Below, we highlight key differences in limits, availability and more between stacked versus unstacked auto insurance.
Higher coverage limits
Standard coverage limit
Number of Vehicles
Requires at least two insured vehicles
Requires at least one insured vehicle
Typically more expensive
Typically Less expensive
Not available in every state
Available in every state
Differences in Coverage Limits
Stacked coverage allows your UMBI coverage limits to potentially double or more. With stacked coverage, your limits only total to the per-vehicle limits specified in your auto policy.
Differences in Number of Vehicles
To stack coverage, there needs to be at least two or more insured vehicles. If you have only one auto policy and a single insured vehicle, the coverage will automatically default to unstacked.
Differences in Cost
You will typically see higher auto insurance premiums when choosing stacked coverage over unstacked coverage. This is due to stacked coverage allowing for a single car insurance claim to tap into the coverage limits of other insured vehicles to increase your total coverage.
Differences in Availability
Stacked coverage is available in only 32 states (see our list earlier for states that allow coverage). In states that allow stacked coverage, individual insurers may include anti-stacking provisions that prevent policyholders from stacking their coverage. Unstacked coverage, on the other hand, is available in every state.
How To Choose Between Stacked and Unstacked Insurance
When buying auto insurance, choosing between stacked versus unstacked insurance will depend on your budget, needs and accident history.
Can Your Budget Accommodate a Higher Premium?
Stacking your UMBI coverage limits typically comes with a higher car insurance premium. Paying a little extra can be worth potentially doubling your coverage limits. However, your budget would ultimately determine whether purchasing stacked coverage is possible.
What Does Your Claims History Look Like?
Increasing your UMBI coverage limits may be more useful for those who get into accidents more frequently. If you're a safe driver and have a clear or minimal accident history, then paying extra for stacked coverage may not be worth the extra cost. Stacked auto insurance may even be less necessary for low-mileage drivers (typically 10,000 miles annually or fewer) who have even less exposure to accidents.
Are Your State's UMBI Limits Too Low?
Stacked auto insurance may offer extra peace of mind if your state has low UMBI coverage limits. UMBI minimum required limits in New Jersey, for example, are only $15,000 per person — comparably low when $25,000 is the most common minimum requirement in states that require UM/UIM coverage. Increased coverage limits via stacking would be more capable of handling severe injuries if the at-fault driver has no liability insurance or not enough coverage.
Does Your State Have a Lot of Uninsured Drivers?
Stacking your UMBI coverage can be much more useful in states with a higher percentage of uninsured drivers. The states listed below are among those with the highest percentage of uninsured drivers. If you live in any of these states, then stacking your coverage may be worth considering:
New Mexico: 21.8%
Rhode Island: 16.5%
Stacked auto coverage may not be as useful in states with a low percentage of uninsured drivers, like New Jersey (3.1%) and New York (4.1%) because the at-fault driver's liability coverage would pay for your losses.
Pros and Cons of Stacked Insurance
Higher UMBI coverage limits
Peace of mind
Limited state availability
Synergizes with family auto policies
Property damage is not stackable
Not for single-vehicle policies
Stacked Insurance Pros Explained
Higher UMBI coverage limits: With stacked auto insurance, you can potentially increase your UMBI coverage limits to double or more.
Peace of mind: Rest easier knowing that even severe and costly auto-related injuries may be covered by stacking your coverage limits when you're in an accident with an uninsured or underinsured driver.
Synergizes with family auto policies: Family policies often have multiple insured vehicles under a single policy. Parents may like the idea that their more risk-averse teenage drivers have additional UMBI coverage if they need it.
Stacked Insurance Cons Explained
Higher premiums: Insurers will typically charge higher premiums to reflect the potentially increased UMBI coverage limits in a single car insurance claim.
Limited availability: Stacked coverage is available in only 32 states and some of those states may only allow one type of stacking. Even in states that allow it, some insurers may prohibit policyholders from stacking.
Property damage is not stackable: Only UM/UIM bodily injury coverage is stackable. You can not stack coverage limits for UM/UIM property damage claims.
Not for single-vehicle policies: If you don't have more than one insured vehicle, then stacked coverage will not be an option for you.
Do You Have Uninsured/Underinsured Motorist Coverage?
Whether or not you stack coverage, UM/UIM coverage can be invaluable when you're in an accident and the at-fault driver doesn't have car insurance or not enough coverage to cover all your hospital bills.
If you want to add UM/UIM to your auto policy or you're shopping around for a lower price on a new policy, SmartFinancial can help. We analyze 200+ partners in your area based on your answers to a quick online questionnaire. In a few minutes, we match you with an auto policy that may meet your coverage needs and budget. Ready for your free auto insurance quotes? Enter your zip code below to get started.
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