On Monday, Gov. Janet Mills signed a proposal into law to allow Mainers to install small, portable solar energy systems in their homes.

The measure from Sen. Nicole Grohoski, D-Ellsworth, allows electricity customers to use certain small solar generation and battery systems, which plug directly into wall sockets, similar to gas generators. The panels are portable, unlike traditional solar panels.

The Democratic governor signed the bill Monday after the Legislature gave it final approval last week. The House passed it mostly along party lines, while the Senate gave it broader approval apart from a few Republican opponents.

The governor’s signature on the bill, which will take effect 90 days after lawmakers adjourn, comes as Mainers face high electricity prices driven largely by natural gas prices spiking in New England and as the conflict with Iran drives up energy prices generally.

Proponents argue the small, plug-in generators could offset a household’s electricity usage and lower monthly utility bills, all for a significantly lower upfront cost than larger-scale, more traditional solar outfits. One estimate from Rep. Gerry Runte, D-York, found an 800-watt system could save an average Central Maine Power Co. customer more than $250 annually.

Twenty-eight states — including nearly every state in New England — are considering similar “balcony solar” proposals, according to an analysis by Canary Media.

Officials in the United Kingdom announced in March that plug-in solar panels would “be in shops within months,” noting they have already been adopted elsewhere in Europe.