Keene’s Department of Public Works is proposing a change to water rates. The idea is to encourage conservation by setting a two-tiered rate on households. Water use up to a predetermined average usage rate would be charged one rate; any use beyond that point would come at a premium.

The idea, according to paid consultant Dave Fox, is to help ensure the resource is being used efficiently. He also said it could help with affordability, though that seemed a stretch to point out.

The threshold between essential and non-essential water use would be 4,500 gallons, or 600 cubic feet, a quarter, Fox told the Keene City Council’s Finance, Organization and Personnel Committee last Thursday. He estimated someone using that much might save a dollar or two on their quarterly bill, but said the average residential use is twice that — 9,000 gallons. For that average user, the bill would rise $11.50 per quarter.

So it’s a price hike, but with an escalator. Essentially, the city would be providing a disincentive to use a lot of water — think baseball’s luxury tax.

It’s not a bad idea to charge more to those who take this valued and, to this point at least, still limited, resource for granted. Providing a disincentive to draw out that long, hot shower or vie with neighbors for greenest lawn makes sense in an area that in recent years has annually experienced near-drought conditions, or worse.

There are only two ways the city can reduce water usage. It can put a hard limit on the supply, by turning off the taps or mandating water-use restrictions. Or it can convince users to cut back. This is the latter approach. It also stands to add to the amount of money in the city’s water account. In that way, we guess, it’d be a win-win idea: the city either makes money — presumably to put away toward some future water project — or the disincentive works and use is reduced, in which case a resource is preserved.

That’s the big picture. However, like most public policy decisions, the devil will be in the details. So as city councilors ponder the proposal tonight, they’d do well to ask, or answer, a few questions.

To begin with, as former councilor Terry Clark has asked in a letter to the editor, if conservation is the goal, why are business and industrial users not part of the plan? We’d bet the city’s two beautiful golf courses use more water than many residents combined, as do car washes, large stores and manufacturers, and others. And what about Cheshire Medical Center, Keene State and other institutional/nonprofit users? To get at real water savings, it would seem these entities ought to be part of the plan, even if their trigger for the more costly rate is set higher. Yet as Clark noted, the city actually charges commercial users less; they effectively get a bulk discount. That’s a huge, hypocritical issue if you’re trying to sell city residents on higher rates as a means to “save” water.

Councilor Raleigh Ormerod raised another good point last Thursday, which Clark echoed. How will multi-family residences be dealt with? If they don’t have separate water meters, most would likely fall well over the threshold for the higher rate. That could prove a burden on lower-income renters who pay for their water. It could also be patently unfair in situations where a high water user shares a meter with someone who uses far less.

It may be possible that the city could track such situations and deal with them in some way, but if so, the public deserves to know how that would work before it’s implemented.

The idea of giving the city’s water users — preferably all of them — an incentive to conserve is a good one. But before passing a plan that taps the wallets of most city residents, councilors should make clear why the biggest users aren’t being held to the same standard, and how they’ll equitably calculate rates and usage for multiple-unit buildings.