Federal health officials and state exchange leaders may be pleased with enrollment and plan choices in many places, but long-term financing is a puzzle that still must be solved.

More than $4 billion in federal funding has been granted to help states create health insurance exchanges, but starting in January, that federal establishment funding will no longer be available. While HHS may have its own budget for Healthcare.gov and the 34 states served by it, the rest of the state exchanges will have to be financially self-sustaining.

There are a variety of approaches being taken that have their own benefits and risks, although most are relying on strong enrollment to bring in adequate revenue, as Sarah Dash, policy vice president at the Alliance for Health Reform, and colleagues highlight in a report for the Commonwealth Fund.

Most states are levying fees on plans sold through the exchange as their primary financing vehicle, with assessments on monthly premiums ranging from 1 to 3.5 percent, the percentage Healthcare.gov is using.

Colorado, Connecticut, Kentucky, Maryland and the District of Columbia are also levying fees on health plans sold off-exchange — an unwelcome prospect for some insurers with minimal or no participation in public exchanges — while others are using funding from the general budget.

California, Hawaii, Idaho, Massachusetts, Minnesota, Nevada, Oregon and Washington are all using an assessment on exchange plans only. And that raises a question for Dash, who’s also a Georgetown policy research: “Will enrollment be sufficient to generate adequate revenue?”

Some states with fairly high exchange levies are hoping they can lower the fee if enrollment increases this year.

Covered California is placing a $13.95 per member per month (PMPM) fee on exchange plans for 2015 plans, as it did in 2014. But if enrollment turns out to be low, tens of millions of dollars in revenue will be lost.

Connect for Colorado places a 1.4 percent premium surcharge, plus a broad-based per-member fee on all health plans sold in the state. This year that per-member per-month fee was $1.80; for 2015 it’s being lowered to $1.25, after a better than expected enrollment turnout.

Meanwhile, Minnesota's exchange, MNSure, is increasing its premium fee levied on exchange plans from 1 percent to 3.5 percent, after multiple technology problems that saw the early departure of the executive director.

Other exchanges are also increasing their levies. Nevada’s Silver State Exchange, which saw low enrollment and numerous technology woes in its first year, is increasing its fee from $4.95 PMPM to $13 PMPM.

Cover Oregon, probably the poster child for failed HIX technology, is increasing its fee for modestly, from $9.38 PMPM to $9.66, although that’s still quite high, all exchange fees considered. Washington Healthplanfinder has added an additional $4.19 PMPM assessment on marketplace carriers, on top of its existing 2 percent premium tax.

Other state exchanges are sticking with their fees from 2014. Connecticut’s Access Health CT is levying a charge of 1.35 percent of premiums, Hawaii’s Health Connector and Maryland’s Health Connect are both keeping a 2 percent premium levy and Kentucky’s Kynect is continuing a 1 percent premium fee.

And some states are still considering their options.

New York’s NY State of Health, the second largest state exchange, is relying entirely on state appropriations — for now at least. The exchanges for New Mexico, Rhode Island and Vermont all have temporary funding from either the state or feds and are mulling their options.

The question in the case of exchange-only fees is: Will it be enough to finance the HIX?

It could be argued that the broad-based assessments on both exchange and nonexchange plans leaves all insurers benefiting “from a well-functioning health insurance marketplace that increases the ranks of the insured,” write Dash and colleagues in the Commonwealth Fund report.

The broad-based assessments could, “help level the playing field between insurers selling on and off the marketplace,” they argue. “Such assessments may also reduce the overall assessment amount per insurer and relieve pressure on the marketplace to achieve higher enrollment levels.”