Two employers can buy the very same health plan and get bills that look nothing alike. Most of the time the reason is not the plan. It is the way the carrier builds the rate.
What tiered rating means
On a tiered rate sheet the carrier publishes one price for each coverage tier. The usual four are employee only, employee plus spouse, employee plus children, and family. Every enrolled employee pays the price for the tier they picked, no matter how old they are. A 27 year old and a 58 year old who both take employee only coverage cost the group the same amount.
That makes the math simple. Count how many people sit in each tier, multiply, and you have the monthly bill. It also makes the employer contribution easy to write down, because you can say what the company pays per tier and everyone can check their own paycheck against it.
What age rating means
On an age rated sheet the carrier publishes a rate per person based on age. Dependents are rated too. Your monthly bill is the sum of the individual rates for everyone enrolled.
Carriers usually group ages into bands rather than pricing every single year, and this is the part that trips people up: the bands are not the same from one carrier to the next. One carrier may break at one age, another may break somewhere else, and a third may price single years through part of the range. So you cannot take a census, memorise one carrier's bands, and assume the next quote will behave the same way.
Where each one shows up
In Oregon, small group medical is usually tiered. In Washington, many groups are age rated. If you have employees in both states, or you are moving a group across the line, expect the rate sheet to change shape even when the coverage looks familiar.
What changes at renewal
Under tiered rating, a person's premium only moves when their tier moves or when the whole rate sheet changes. Someone gets married, adds a baby, drops a dependent, and the tier changes. Otherwise the number holds until renewal.
Under age rating, a birthday can move a premium on its own. Nobody changed plans, nobody added anyone, and the bill is still different. Over a few years a stable group can drift upward simply because the same people got older. Hiring changes the total both ways, and faster than most employers expect.
Comparing quotes from both
Do not compare a tier price to a per person rate. Build the real monthly total for your actual census under each quote, then compare those totals. Then do it again with a couple of plausible changes: one hire, one retirement, one new spouse. That second pass is where the difference between the two methods shows up.
If you want a hand reading two rate sheets side by side, call the office and we will walk through them with you.