If you live in Colorado and you want to install a new pool or hot tub, you might be required to offset your carbon footprint in solar panels, heat pumps, or cold, hard cash.

That’s because a growing number of Colorado communities are adopting a “renewable energy mitigation plan” (REMP), which is a program aimed at offsetting the greenhouse gases that outdoor features such as pools and hot tubs, as well as driveway snow-melt systems and gas grills, can create.

According to Bonnie Muhigirwa, Aspen’s chief building officer, exterior energy use is 50 percent of the total home energy use for some of their residences. REMP is meant to pay for this use.

It works like this: If you live in a community that has adopted REMP and you want to put in an amenity like a hot tub, you also have to pay a bit extra by also installing an energysaving system such as photovoltaic solar panels, hot water solar, wind or small hydropower projects, or geothermal heat pumps.

Jessica Burley, Breckenridge’s sustainability and parking manager, said “Solar PV is the easiest and most economical.”

So far, the REMP program does not seem to have impacted consumption of outdoor amenities such as snowmelt systems or fire pits. Officials in towns and counties that already have REMPs say they have had little effect on sales of pools and spas.

“These are often multimilliondollar homes,” said David Samuelson, the building official in Telluride, which has adopted REMP. “If they want a hot tub, they are going to have a hot tub.”

In many communities, homeowners can also pay a mitigation fee — $1,600 for a hot tub in Telluride — which Samuel said is basically chump change for most homeowners there. In Aspen, carbon dioxide emissions for outdoor facilities are calculated based on their consumption of kilowatt-hours or in British thermal units.

That emission number is then translated into an offset of an onsite photovoltaic solar panel or a cash payment.

For example, a 7-square-foot hot tub would require 0.64 kilowatts of photovoltaic panels or a $2,072 payment. A 15-by-30 foot pool would require 32 kilowatts of photovoltaic panels or a nearly $103,000 cash payment.

Since its program began in 2000, Aspen has collected $18.3 million in REMP fees, which have gone to a variety of programs, such as promoting energy efficiency upgrades and rebates..

And this year, Aspen also put an energy limit on new residences of 200 million BTUs for outdoor use. (The pool and spa in the above example consume about 165,400 BTUs, according to Aspen’s REMP worksheet.)

Summit County is the latest community to embrace REMP, which announced its adoption beginning in August. It now joins Aspen and Pitkin County, which in 2000 were among the first to implement REMP. About a dozen other communities, including Crested Butte, Carbondale, and Eagle County, have adopted similar programs.