Yesterday Bob Brown celebrated the Greens’ ascension to party status and a share in the Senate balance of power with a National Press Club speech.

In truth, no one really has the balance of power in the sense of being able to guarantee passage of bills. Steve Fielding and Nick Xenophon are closest, but even they could be sidelined if Coalition Senators decide to cross the floor, which, given the level of Coalition indiscipline these days, cannot be ruled out. What the Greens, Xenophon and Fielding — Xenofield, anyone? — all have is a veto over government bills. Any one of them could stop the passage of government legislation not supported by the Coalition.

But that aside, welcome to the political food chain, guys. Now you have to work out how much you want to trade off policy purity for the sake of getting part of what you want. On the basis of Senator Brown’s speech yesterday, not a lot, but it’s early days, and a good player doesn’t tip their hand ahead of negotiations.

On an emissions trading scheme, it seems likely the Greens will want bigger targets than the Government can live with politically, and will want to direct compensation to households not in the form of cash but in energy efficiency measures such as insulation and solar power systems.

Focussing on household efficiency measures makes environmental and economic sense. They will reduce demand for electricity and gas and pay for, or substantially offset themselves, over time. But it’s political nonsense. Voters won’t accept a new solar system in exchange for higher grocery, power and fuel bills.

The Government will be flat out linking cash in hand via tax cuts to an ETS, let alone some solar panels and Bradford batts. No deal, chaps. The best the Greens might do is negotiate a scheme whereby green-minded households can elect to take a solar heater instead of cash.

And if the Government’s emissions targets are too high under the ETS, will the Greens join the Coalition in knocking it back? That’d be a good look.

An ETS is only one of dozens of issues where the Greens will have to work out what they’re prepared to live with. Decisions, decisions. The agenda outlined by the Greens yesterday is decidedly left-field – and pricey. A big increase in foreign aid. Mat and pat leave. Aggressive support for human rights. Oh, and a massive increase in the pension level.

I might have missed it in the coverage but no one has asked how the Greens will fund these huge Budget items. They’re big kids now — they should be detailing what taxes they’ll raise or expenditure they’ll cut (hmmm… defence comes to mind), or whether they’ll eat into the surplus.

It’s all smiles at the moment but the Greens, in their new position of responsibility, will discover their own version of the Peter Garrett problem. In deciding to become a major-party politician, Garrett opted for a world of compromise, imperfect solutions and negotiations — but it’s the price of having real power. He has been castigated by his former environmentalist allies ever since as a sell-out.

Brown and co, unless they stand on principle on every single issue, now face the same fate. Supporters will be angered at the deals their politicians make and the compromises they reach. Bob Brown might discover that much of his long-standing lustre wears off. But he’ll be making more of a difference than he has to date.

Oh, and Brown took the opportunity yesterday to announce that Ben Oquist returns to the Greens as his chief of staff, after a stint as a lobbyist. Given their Crikey spats, that should make for some pleasant interactions with Christian Kerr at The Oz.