As a rule of thumb, you should estimate that you can reduce your auto insurance by 10-15% by combining your automobile insurance with the same carrier as your homeowners or renters insurance. This discount could be applied to your auto insurance or you homeowners insurance. For example, I received a 10% discount on my homeowners insurance because I had my auto insurance with the same insurance provider.
It’s important to note that despite this discount, you should still shop around to get homeowners and auto insurance quotes from separate providers. I did this and was able to save over $500 per year even after having my homeowners increase because I was no longer getting the discount.