Microsoft this week boosted by 28% its claim of how much enterprises can save by deploying Windows 10.

The revised estimate came from a Microsoft-commissioned analysis first done in mid-2016 by Forrester Research. Then, Forrester said the per-worker savings over a three-year stretch would be $404. To reach that number, the research firm interviewed four Microsoft customers that had begun moving to Windows 10, then modeled a hypothetical organization with 24,000 Windows devices, and a large number of mobile workers among the 20,000 employees. Using that pretend company, Forrester forecast the difference between running Windows 10 and retaining Windows 7.

Late last year, Forrester interviewed another quartet of Windows early 10 adopters, then added that data to what it had originally. The new per-employee savings: $515 over three years, a jump of almost a third.

"This updated study helps provide further evidence that Windows 10 can drive significant cost savings," said Craig Dewar, a director of marketing on the Windows Commercial team, in a Tuesday post to a company blog.

According to Forrester's new projection, the concocted company would spend about $4.4 million on the Windows 10 deployment, slightly more than the 2016 number. That amount did not include the cost of the Windows 10 licenses, since it was assumed the firm was on a volume licensing agreement with Software Assurance.

Meanwhile, Forrester claimed that the organization would save approximately $14.7 million with Windows 10 during the same period, an increase of $2.3 million over the earlier estimate. Although it was difficult to pin down every change in Forrester's numbers to locate the additional savings, the most substantial were relatively easy to spot.

The largest savings was again attributed to a boost in mobile worker productivity; $7.3 million in savings -- $1.5 million more than the first go-round -- Forrester said. The difference between the two estimates came from Forrester increasing the percentage of the workforce labeled as "often mobile," and boosting the percentage of "time spent on device-intensive tasks affected by Windows 10."

Forrester's increase in the number of mobile workers -- the total climbed by 460 employees -- was the biggest factor in the changed estimate.

Other cost savings that Forrester revisited included simplified, self-serve application delivery ($2.4 million, up $500,000); faster boot times ($1.8 million, flat) and security improvements ($1.3 million, also flat).

But Forrester also added a new item, "New or Retained Sales Opportunities," that analysts assigned a value of $1.2 million. In its report, Forrester cited an example of how a company might see that big-time benefit. "The IT architect for a European telecom and ISP highlighted the potential risk to their business and how Windows 10 can provide some strategic value, saying, 'If a salesperson goes to a customer with his Windows 7 device and says, "We will give you a Windows 10 environment," it's probably not the best thing to show. Instead, we want to be a showcase to our potential customers.'"

The new projection included a new cost section to account for the constant updating and upgrading that businesses must do under Windows 10 new maintenance mandates. "The primary management cost associated with Windows 10 that does need to be included is managing Windows-as-a-service updates," the report noted. The initial report lacked such a cost calculation.

But Forrester's number was piddling: just $157,000 over three years for the entire enterprise. Forrester got there by assuming two feature upgrades annually -- in 2016 there was just one, but Microsoft's promised a pair this year -- and an additional 40 hours of IT time for each of those upgrade.

The bottom line, said Forrester and Microsoft, was that the migration to Windows 10 would pay for itself -- the breakeven point when savings equal costs -- in 14 months, a month more than earlier.

The revamped financial analysis conducted by Forrester can be retrieved from Microsoft's website. The 2016 version can be found on the Web.