Microsoft signed an agreement with GE today to purchase every last bit of the wind energy from GE’s brand-new 37-megawatt Tullahennel wind farm located in County Kerry, Ireland for the next 15 years.

This is a big deal on several levels. First of all, it means Microsoft will be using a clean energy source to power at least some of its cloud data centers in Ireland. That will likely result in a lower energy bill for Microsoft, while reducing the pollution related to running cloud services.

But this could have an impact beyond the data centers as Microsoft and GE are working on a battery technology that captures excess energy from each wind turbine. If there is excess capacity captured by this method, Microsoft and GE could give it back to the Irish energy grid.

Christian Belady, general manager, Datacenter Strategy at Microsoft says this is a continuation of the relationships Microsoft has built up in Ireland, and the agreement could bring multiple winners. “Our commitment will help bring new, clean energy to the Irish grid, and contains innovative elements that have the potential to grow the capacity, reliability and capability of the grid. This will make it easier to incorporate new clean power sources like wind energy, and that is good for the environment, for Ireland and for our company,” he said in a statement.

One of the things about cloud computing is that there has always been a perception that it could be greener than other forms computing, but the fact is that really depends on the energy source. In recent years as the biggest companies from Apple to Facebook to Google to Microsoft have built new data centers, they have built them with energy efficiency in mind.

As an example, Apple signed an $850 million agreement in 2015 to purchase 130 megawatts of solar power over the next 25 years. When Facebook was designing its data center in Prineville, Oregon, even back in 2011 it was thinking about energy efficiency.

It would be nice to think this is about some of the biggest companies being good corporate citizens, and that could be part of it, but the reality is that it’s in their best economic interest to build green data centers that cost less to run. If they produce a smaller carbon footprint in the process, it’s a happy outcome.

Microsoft’s announcement today represents just a fraction of the company’s 600 megawatt clean energy procurement worldwide.