The bill to mandate solar water heating on new-home construction is an idea many in Hawai'i want to support.

This includes The Advertiser, which supported the bill, believing that even the extraordinary step of a mandate is justified to curb Hawai'i's heavy, expensive dependency on fossil fuels.

But a closer reading of Senate Bill 644 reveals serious flaws, introduced late in the legislative session, to appease the gas lobby. Lawmakers added an "escape hatch" that allows builders to choose petroleum-based gas — a fossil fuel — instead of solar.

Specifically, builders of new homes can avoid the requirement to install a solar water heater by opting instead to equip the home with a "tankless" gas water heater, as well as one other gas appliance.

Many builders may see this as a cheaper way to fulfill the mandate. Their opting out will reduce the numbers of homes fitted with solar panels, especially since the bill also would end the solar tax credits the developers now can claim.

Proponents counter that this option, which they admit is a concession to the gas lobby, has benefits. A tankless gas heater only heats water as it's needed and does so much more efficiently than electric models. So if the mandate gives a bump to the gas alternative, some fuel efficiency has been achieved anyway.

But the gas sold in Hawai'i is not the natural gas in such abundant supply on the Mainland, but is manufactured from imported petroleum.

Such a loophole is hardly a strong mandate for using renewable energy.

Gov. Linda Lingle may find it politically difficult to veto this bill, since it still may incrementally advance her own renewable-energy agenda.

She may conclude that some developers won't want to absorb the costs of fitting the subdivision with a gas tank or connecting the project to the grid which, in many parts of the state, may be a good distance away. These builders may opt for solar panels.

And there is also political reality: There is enough support for a bill touted among the session's chief accomplishments for lawmakers to override her veto.

However, even if this bill becomes law with all its flaws, it's critical that legislators circle around it next session and close as many gaps as possible before the mandate takes effect in 2010. They should, for example, flesh out the standards and inspection process to ensure quality control.

The solar mandate should also be strengthened. For example, gas heaters could be allowed, but as a backup rather than primary source, which would be solar.

These would be improvements over the current bill. Compromise is inevitable in the lawmaking process, but government can't let the politics of appeasement divert the state from the true path toward energy independence.