There’s a gaping loophole in the state law requiring new homes to be built with solar water heaters. And if the Legislature fails to stitch together a stronger variance provision, it will set back progress toward Hawaii’s clean energy aspirations.

Nine years ago, Republican Gov. Linda Lingle signed the first-in-the-nation legislation hailed as a key to helping us lose our title as the most oil-dependent state. However, while the so-called solar water heater mandate asserts that a variance — an exemption — will be granted in rare cases, in recent years, more than 30 percent of the 14,375 new homes built were constructed without solar water heaters, with the state approving 99 percent of requests for exemption.

The loophole can be traced to a list that exempts single-family homes from the mandate in cases of: inadequate sunlight; a cost-benefit analysis deeming solar water heater installation too expensive; or the installation of at least one gas appliance in the home, in which case it’s OK to go with a gas-fueled “demand water heater device” rather than a heater powered by renewable energy. The vast majority of variances secured under the flimsy law are due to that last item — the gas appliance provision.

The trend is rightly sounding alarms in the environmental community as the first phase of Ho‘opili’s 11,750-home development on Oahu’s Ewa Plain is beginning to take shape. Last year, developer D.R. Horton promised green design elements, with solar hot water heaters on the list of features that should be “standard in any 21st century project.” But last month, when the the Texas-based company — the largest home construction outfit in the U.S. — advertised interior home features for the development’s first phase, on the list was a tankless gas water heater. No mention of solar hot water.

Typically, builders favor gas water heaters to keep up-front costs down. Installation of the average gas tankless water heater is $1,500, while a solar water system can add up to $6,000 to the price of a new home. However, solar systems result in greater long-term savings tied to reliance on renewable energy rather than fossil fuels.

Hawaii Gas has been working with Ho‘opili on supplying gas to the new development — the largest housing project in the islands in at least two decades. So far, just nine variances from the solar water heater mandate have been granted for Ho‘opili homes. But construction is just getting started on the first phase, which is expected to include 293 houses, with the first few slated for delivery this summer.

Now is the time for state lawmakers to toughen up this easy-to-circumvent law. Failure to do so means we can expect to see D.R. Horton, which has touted pride in a “commitment … to lead the way” in sustainable design, leave us with an even greater dependence on imported oil. Other developers, too, will be emboldened to pursue waivers.

Senate Bill 1121 aims to close the loophole with an amendment that would limit variances to cases in which solar water heating is “impracticable and cost-prohibitive, and if no renewable energy technology system can be substituted as the primary energy source for heating water.” It also clarifies that a variance would be granted only when the applicant will also be the resident-owner of the home. So, a gas-fueled heater would be installed as a last resort. And each application must be based on the prospective resident’s circumstances — rather than those of the builder.

The proposal has the potential to uphold the intent of the law, which has echoes of landmark legislation signed by Gov. David Ige that sets Hawaii on a trajectory to become the first state to achieve energy independence in the electricity sector (by 2045).

The need to amend the solar water heater mandate is “particularly sharp” now, as “substantial new residential tracts are being developed,” according to SB 1121. Earlier this week, though, it had not been scheduled for a hearing, a key first step for any bill to progress. Such neglect is enough to make consumers wonder whether when it comes to the hard work of building a sustainable future, Hawaii’s lawmakers are more talk than action, more green-minded show than go.