Figuring out a building’s energy efficiency potential without actually entering the building isn’t easy. Using a software analytics approach can get you there, if you’ve got the right data -- preferably, both from the building itself and from the utilities that serve it.

Boston-based startup Retroficiency has been working on the building side of that equation with real estate data analytics software to better target cost-effective efficiency retrofits. On Wednesday it announced a $3.3 million series A round from Point Judith Capital, along with the acquisition of a company with software designed to parse power meter and utility data, giving it insight into both sides of the equation.

The acquisition is the Clean Energy Solutions (CES) division of NexAmp. The Massachusetts-based renewable energy developer created CES to provide energy efficiency analytics for its green power customers, but the same software tools bring a useful new set of capabilities to Retroficiency’s efficiency auditing plans as well, CEO Bennett Fisher told me in an interview.

“They’re really very complementary products, serving two separate sides of the market,” he said. Retroficiency’s focus has been to mine real estate data, weather information, past retrofit project records and other such building-side data to deliver a snapshot of a building’s energy use and potential for efficiency gains. It raised an $800,000 angel round in March led by World Energy Solutions, and has a customer list that includes Jones Lang LaSalle and SAIC.

NexAmp’s CES, on the other hand, attacks utility and meter data to tease out power use data for buildings that lack building management systems or other sensor and control systems. It’s an idea that’s being put to the test by startups such as Waltham, Mass.-based First Fuel, which raised $2.4 million in September to tackle utilities as customers, as well as San Francisco-based SCIEnergy, which is pulling building meter and submeter data to cross-reference with its building efficiency management software.

With its acquisition of CES, Retroficiency can now help its energy services or real estate portfolio management clients delve more deeply into utility data. It can also pitch its building expertise to utilities, smart grid companies or other meter-side players seeking more insight into buildings, Fisher said.

The end goal is to integrate the two into a complete system, although that’s still the “pot of gold at the end of the rainbow” for the newly married companies, Fisher said. For now, the two sets of software are “already being built on the same platform, using the same stack in terms of technology, so it will really be easy to flip between the two,” he added.

Terms of the acquisition were not disclosed, though Bennett said that it was not predicated on the company’s $3.3 million round. Interestingly, Retroficiency investor Point Judith also took part in a $6.5 million investment into NexAmp in February 2010, indicating the investment firm’s role as matchmaker between the two companies.

Zaid Ashai, general partner at Point Judith, told me that one of the key values of a Retroficiency-CES mashup will be to create tools that could help small commercial buildings -- those under 50,000 square feet or so -- find ways to enter the energy efficiency market. Small to mid-size commercial properties tend to lack sophisticated building automation systems, if they have systems at all, which means they need data analytics expertise to figure out which efficiency projects are worth the effort before they start investing in them. 

Ashai declined to discuss how NexAmp’s sale of its CES division affected the value of Point Judith’s 2010 stake in the company. He did mention, however, that CES has been working with a couple of large government-sector customers, including the U.S. Army Medical Command in partnership with facility management firm VW International.

Point Judith seems to like energy data analytics software startups, by the way. In February it led a $4 million Series A round into Washington, D.C.-based Earth Aid, which is working on software to pull utility data from public sources and feed it back to customers to track and manage energy use.