Commercial property owners in Boston have a big homework assignment due May 15 but some are praying for an extension and warning that their grades could be misleading.

By May 15, owners of an estimated 1,050 commercial buildings that are 50,000 square feet or larger are required to submit data on 2013 power and water usage to the city. The Building Energy Reporting and Disclosure Ordinance (BERDO), approved by the City Council last May, was submitted by former Mayor Thomas Menino with the stated goal of reducing greenhouse gas emissions.

While sympathetic to its green-friendly goals, some real estate and business groups say the law is confusing, burdensome to smaller landlords and could scare away potential tenants when building data is publicly released in coming years.

Many property owners were becoming anxious because they hadn’t received any outreach from the city until late January, said Greg Vasil, CEO of the Greater Boston Real Estate Board.

“When you try to change someone’s behavior, you really have to reeducate them and unless you have a serious effort, that’s not going to happen here,” Vasil said.

For now, there are no penalties for energy-hogging properties, only potential fines for owners who fail to submit the required data on time. The ordinance calls for fines of up to $200 a day and a maximum of $3,000 per year for each building that fails to report.

The city began its outreach on Jan. 22, sending a letter to all landlords whose properties are required to report this year, based upon assessors’ records. The law applies to all commercial buildings that are larger than 50,000 square feet, and multiple commercial buildings on the same lot that total over 100,000 square feet.

The law will be phased in through 2017, eventually encompassing all commercial buildings over 35,000 square feet and all multi-family buildings with 35 or more units.

It makes landlords largely responsible for gathering the energy data from tenants and utilities and submitting it using an EPA web site. And it requires utilities to make whole-building data available to landlords. NStar will activate a web portal in late February where building owners can look up last year’s data, spokesman Mike Durand said.

Too Burdensome

At least one group, the Newmarket Business Association, is calling on the City Council to delay the ordinance so it can be overhauled.

“We’ve embraced green technology and reducing our carbon footprint, but that’s not what this is about,” said Sue Sullivan, the association’s executive director. “This is really just a revenue source for the city.”

City officials say most landlords shouldn’t find it especially onerous to comply.

They’re required to use Energy Star, an EPA web portal that ranks commercial buildings’ energy efficiency, to enter their data and send it to the city. Nearly half of the total 1,800 buildings subject to the ordinance already use Energy Star, said Brian Swett, the city’s acting chief of environment, energy and open space.

“A significant portion of building owners are already familiar with this,” he said. “If you’re starting from scratch, I would convene a group of folks that have this information at the ready: maybe your onsite building engineer, your leasing agent or your property manager.”

In a City Hall interview this week, Nikhil Nadkarni, the city’s climate and buildings program manager, gave a demonstration of how use the Energy Star Portfolio Manager program to create the required spreadsheet and submit it.

For each building, the website asks owners to submit data such as square-footage, hours of operation, number of employees and workspaces, and types of building use. Owners can enter energy data manually or upload it from the utilities’ sites beginning around March 1.

Portfolio Manager uses the data to calculate year-to-year energy use trends, energy use per square foot and greenhouse gas emissions.

In the first year, the city will not publish any data on individual buildings, Swett said.

“All we’ll be reporting is compliance and general trends by sector,” he said.

But property owners are already fretting about what types of data will be released in coming years. Some in the industry say the data could stigmatize low efficiency properties. The reporting system doesn’t distinguish between buildings that have a single electric meter versus those that meter individual tenants, for example.

“Owners are afraid they’re going to be put at a disadvantage by that,” said Daniel Ozelius, senior vice president for Jones Lang LaSalle’s property management division. “We’re going to give the city all this data. The question is how they’re going to report it out.”

An advisory committee including real estate developers will make recommendations to the city on those details for next year.

New York, San Francisco and Washington, D.C. have passed similar ordinances in recent years. The first year is usually the hardest for building owners, according to an executive for a Boston-based company that helps building owners analyze energy use.

“(In New York) it was tougher to get reliable data in the first year than the second and the third,” said Barun Singh, chief technology officer for WegoWise Inc.

Email: sadams@thewarrengroup.com