In the past 10 days, twice as many Utahns signed up for solar panels every day than usually do in a month

( Francisco Kjolseth | Tribune file photo ) Artspace Solar Gardens, at 850 South 400 West in Salt Lake City, is the first net zero mixed-use energy building with onsite solar production in the state of Utah. This week was consumers’ last chance to take advantage of Rocky Mountain Power's current system for crediting power delivered to its grid by residential rooftop solar panels.

More than 4,000 Utahns signed up to install solar panels in the 10 days before Tuesday’s deadline, becoming the last residents who will get credit under Rocky Mountain Power’s current — and more generous — terms for excess electricity delivered to its grid.

More than 3,000 of the roughly 4,300 applications were filed in the final four days.

The utility’s net metering program reduces residents’ power bills by one kilowatt hour for each kilowatt hour they generate. For customers who missed this week’s deadline and sign up in coming years, it’s moving to a new paradigm in which credits will be offered in dollar amounts — 9.2 cents per kilowatt hour through 2032.

It currently charges about 10 cents per kilowatt hour, so the new credits will be worth slightly less than those awarded under the old system.

Ryan Evans, president of the Utah Solar Energy Association, said he didn’t believe the new applicants were motivated solely by the deadline. Applicants had had likely considered installing solar panels before squeezing their paperwork in at the last minute.

“A whole bunch of people who have been on the fence have pulled the trigger,” he said. A lot of customers, he said, “sat out and waited to see what would happen over the course of the year.”

The solar association and Rocky Mountain Power spent much of the last year in closed-door negotiations after the utility proposed replacing the net metering program with a new billing structure last fall.

Solar industry leaders worried that original proposal would to hike electrical rates for solar households, potentially killing their business prospects in Utah.

Whether or not existing net metering customers would be billed according to the new rate structure was a central issue.

Originally Rocky Mountain Power proposed to grandfather any customer who applied to the net metering program before Dec. 9, 2016. That deadline inspired a flurry of 2,000 last-minute applications — just half what this year’s cut-off garnered.

The company, which had received an average of 1,300 applications per month for the six months prior to that cut-off, decided against implementing that proposal.

The new system was established by a settlement negotiated between the utility, solar industry representatives and other Utah interests. Residents who filed for net metering before the close of business on Nov. 14 will be billed according to the old system through 2035.

Last-minute applicants may have yet to install solar panels, though applicants now are required to include specific plans for the installation of solar panels on their house.

The panels must be in place within a year for the applicant to remain in the net metering program.

The company said it did not have data on how many of the 2016 applications have not resulted in installations. Evans said he thinks many applicants wanted to save themselves a spot in the program, but didn’t actually install panels.

“Last year… companies were saying let us put your name in, and you’re good to go,” Evans said.

Last year’s 16,951 net metering applicants still have some time to get their solar array installed. So far, 10,092 net metering accounts have been created this year, according to data from Rocky Mountain Power. Some of those new customers may have filed applications this year.

Going forward, Evans said he doesn’t believe the slightly smaller credit will deter too many Utahns from investing in solar power in the future.

“We’re definitely going to see a steady rate of applications, just not the same furious pace there has been for the last two months,” he predicted.