Hartford - The energy bill passed Tuesday night by the state Senate will drive down the costs of electricity for homeowners and businesses, its proponents insist.

Its critics are just as adamant that the very opposite will happen, and Connecticut's electric rates, the highest in the continental U.S., will rise even higher.

And both sides have been threatening the other with the Hartford politician's equivalent of the monster under the bed: the notorious 1998 vote to deregulate Connecticut's electricity market.

That year, many lawmakers voted for a deregulation bill they didn't fully understand, the conventional wisdom now holds. And the promises that deregulation would cut rates turned out to be wrong, leaving elected officials here to explain soaring power bills to angry constituents.

This year's energy bill, the most sweeping since that 1998 legislation, is an attempt to finally deliver on the promise of retail choice in electricity markets, said Sen. John Fonfara, D-Hartford, the co-chairman of the Energy and Technology Committee, hours before the Senate finally approved the bill, 20-14, after more than three-and-a-half hours of debate.

The bill includes new flexibility for the state's utilities, Connecticut Light & Power and United Illuminating, in their purchases of power from generating companies - leeway that backers of the bill say will let the utilities lower rates and make them more competitive with smaller energy retailers, to the benefit of all customers.

It also cuts into "subsidies" that those who buy their electricity from UI or CL&P are now providing to the energy retail companies, Fonfara said, by requiring those non-utility energy companies to start paying for some of the costs of their customer recruitment efforts, including the mailers they package with utility ratepayers' bills. The costs of such marketing activities are currently paid for by utility customers.

And the bill includes robust incentives for the development of solar power and other renewable energy, backstopped by provisions like a 1 percent rate cap and tax credits that decline over time. Those elements, supporters say, will mean that the solar subsidies will not be permitted to drive rates up dramatically, as the industry groups warn, and that renewable energy companies will be required to drive the costs of their products down over time to stay competitive.

But the legislation is long, complex and dense, leading Sen. Kevin Witkos, R-Canton, to say he was tempted to ask how many of his colleagues had read the whole thing, but "I wouldn't want to embarrass anyone, because I know what the answer is. It's not that many."

Twelve years earlier, he said, "to put your trust in a bill so complex that many didn't know what it did. ... I believe we're asking you to do the same thing today."

But Fonfara insisted the reforms will finally force retailers to lower their prices in ways that benefit individual customers, the ones still waiting for the benefits of deregulation they were promised.

Electricity retailers are "going to have to think faster, smarter, to make their rates drop," he said. "And who does that benefit? That benefits all of us."

t.mann@theday.com