The Miami Dolphins are getting early support from state legislators to use tax dollars to renovate Sun Life Stadium.

A Florida Senate panel on Tuesday unanimously approved a measure (SB 306) that would guarantee $3 million a year for the next 30 years to help pay for stadium upgrades. It’s just the first vote, however, with a final vote coming during the session that starts in March.

But the swift approval could be a sign that the Republican-controlled Legislature will support the deal despite past objections to helping out South Florida sports franchises.

Miami-Dade will use hotel-tax revenue to pay off the bonds. But payments don’t kick in until 2026. Once they do, they get very costly very quickly. The first payment, for example, totals $260,000. The fifth jumps to almost $8 million and the 10th tops $20 million. Payment No. 18 brings the big hit: $118 million comes due in 2042 alone.

The high interest comes from the penalty Miami-Dade must pay in exchange for a repayment plan that lets the county delay by 15 years making it first debt-service payment to the Wall Street lenders who bought the bonds.

“It’s an expensive way to borrow money,’’ said Frank Hinton, head of the county’s bond program. “You’ve got $1.2 billion to pay back. It is a lot of money.”

Because Miami-Dade couldn’t afford a straight-line paydown of the loan — like a home mortgage — the finance team had to be more creative in borrowing the money on Wall Street. Unlike most bonds, these can’t be repaid back early either.