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Did you enroll in an Obamacare plan last year? Your plan will probably auto-renew for 2016 -- but you shouldn't necessarily let it.

That's because plan costs change from year to year. According to a new study from the Kaiser Family Foundation, the consumers who stick with last year's most popular choice (the lowest-cost silver plan) will see an average premium increase of 15% for 2016.

Yet consumers who shop again for 2016 can often find a better deal. The Kaiser Family Foundation found that in 73% of U.S. counties, consumers will be able to find a new, more affordable silver plan. On average, enrollees who switch from last year's cheapest silver plan to this year's cheapest silver plan will be able to save $322 in premiums by making a change for in 2016, the study found.

Average monthly premium increase (in U.S. counties with lower-cost options in 2016)
For a single 40-year-old with annual income of: Who stays in the 2015 cheapest silver plan Who switches to the 2016 cheapest silver plan
$20,000 $28 $1
$30,000 $28 $1
$50,000 $44 $17
Source: Kaiser Family Foundation

Don't let inertia take over. Last year, 47% of enrollees were renewed automatically, the Kaiser Family Foundation says. People who stayed in the most popular plans from 2014 missed out on savings in competitive markets, where insurers were offering better deals in 2015.

Beyond Premiums

While you're shopping around, also be sure to look beyond the premiums. Co-pays, deductibles and prescription drug benefits may be changing too.

ProPublica found last year that some insurers changed the fine print on plan benefits between 2014 and 2015, leaving consumers with higher overall health care costs.

Note that your decision now can affect the tax refund you might get in the spring of 2017. Since coverage subsidies are based on the second-cheapest silver plan in your area, your subsidy amount can change when the plan prices do. Even if you're not going to change plans, be sure to go to to update your income information and check your subsidy for this year.

One word of caution: If you do switch to a cheaper plan, make sure your doctors are still in-network. Getting care from out-of-network health care providers is a sure way to rack up bills, even if you've reduced your premium costs.

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