LOWELL — Mark Andrews and Mashail Arif know being “green” isn’t so easy.

From poor sun exposures to lack of structural integrity of a roof for supporting something heavy, homeowners face many obstacles in having solar panels installed, said Arif, energy manager for the town of Chelmsford.

So both Arif and Andrews, Pepperell’s town administrator, thought their towns’ plans to turn capped landfills into solar farms would help those residents, allowing them to buy credits for power generated at the farms and put them toward their electricity bills. The problem, Andrews said, is that the state won’t let them do it because the region already hit its caps for so-called “net-metering” under state law.

At a rally Wednesday in front of Lowell City Hall to urge state legislators to increase the net-metering caps, Lowell Mayor Rodney Elliott, standing shoulder to shoulder with Andrews and Arif, said it’s “kind of a no-brainer that we move forward” with net-metering.

“We urge state officials to keep solar growing,” said Ben Hellerstein, state director of Boston-based Environment Massachusetts, which organized the rally.

Representatives from Pepperell, Chelmsford and Lowell stood united in calling for state legislators to increase net-metering caps.

Net-metering refers to a system that allows people to generate their own electricity to offset their electricity usage and bills. Power generated from rooftop solar panels, for example, is deducted from homeowners’ utility bills.

If you don’t own panels or windmills, you can purchase credits for such alternative energy from those who generate it, and have it reflected on your utility bills.

Ratepayers often get involved in net-metering deals with a third party because the rates tend to be competitive compared to what they would normally pay to traditional utility companies.

Under state law, power distribution companies, such as National Grid, can only allow a percentage of their highest historical peak loads — or the most electricity consumed by their customers at any one time — according to the information posted on the state Department of Public Utilities.

There is a cap for “public” net-metering facilities that are operated or used by municipal governments and entities, and a separate cap for “private” net-metering facilities. The caps do not apply to facilities smaller than 60 kilowatts in generation capacity.

The cap for National Grid territory is 205.24 megawatt for public net-metering facilities, and 256.55 megawatt for private ones.

The region reached those caps about the end of March, preventing any additional projects from moving forward, according to Hellerstein.

In May, Chelmsford Town Meeting approved a project to lease a capped landfill on Swain Road to create a 750-kilowatt solar farm. A solar-farm, developer to be selected through a bidding process, would offer net-metering to town residents.

“National Grid believes in the importance and value of solar in Massachusetts, at the right price,” the company said in a statement provided by Senior Media Specialist Danielle Williamson. “Due to the combined costs of the state’s solar program and net metering, we continue to believe that raising the caps on net metering is not in the best interest of our electric customers who — even without raising the net metering caps any higher — will experience a $1.5 billion rate impact over the next five years.

“Raising net metering caps is unnecessary for continued solar development in Massachusetts, as evidenced by the volume of solar applications National Grid continues to receive after reaching our net metering cap,” the statement continued. “On behalf of our customers, we are advocating for the development of a sustainable set of policies to continue the growth of solar in Massachusetts without paying some of the highest subsidies in the nation.”

Pepperell already has a contract with Nexamp Capital to turn a 3.5-acre landfill on Boynton Street into a 657-kilowatt solar farm. The 2,000 solar panels to be installed there would produce enough power to keep lights on for about 130 households in town, Andrews said.

“This is a good reuse of the property — the highest reuse advantage,” Andrews said of the landfill.

He added that the project would generate 40 jobs for construction and 5-10 jobs for operation and maintenance of the facility.

“This is the way for residents to tap in to the financial benefit of solar,” Chelmsford’s Arif said of providing residents access to net-metering.

Andrews said he spoke with state Sen. Eileen Donoghue, a Lowell Democrat, and Rep. Sheila Harrington, a Groton Republican, about the issue.

During Wednesday’s rally, he urged lawmakers to support two legislative bills that call for increases to the net-metering caps.

While Lowell is not directly impacted by the caps currently, Elliott said “being able to feed energy into the grid without any limit” is important.

Pepperell Conservation Commissioner Rob Rand said net-metering can provide low-income housing access to clean energy.