The two new data centers that Microsoft Corp. plans to build in South Africa will one day provide cloud computing services to the entire African continent. The power they use, however, will be generated and consumed entirely within South Africa’s grid.

While a decade ago that would have meant buying electricity from the utility regardless of generation source, Microsoft today expects to have a variety of options. Given its commitment to renewable energy, the company may prefer to use wind and solar energy. But in South Africa, that power might not end up being entirely clean.

Many big companies -- and big purchasers of power, such as the U.S. Department of Defense -- are choosing renewables. Since 2008, the top 10 buyers of zero-carbon power alone have created billions of dollars’ worth of long-term demand for wind and solar power, Bloomberg New Energy Finance has seen. Of those companies, five are American technology companies with their own data centers, and one (Equinix) is an American data center operator:

Big Power Buyers Go Renewable

Top 10 corporate procurers of clean electricity since 2008

Source: Bloomberg New Energy Finance

Data as of May 23

Google, the biggest buyer of clean power, was also early to the game, making its first corporate clean-energy purchase in 2010. Microsoft signed its first clean-energy contract in 2013:

Google Moved First

Tech company renewable power purchase agreements

Source: Bloomberg New Energy Finance

Note: Megawatts recorded in year agreement was signed. Data as of May 23

What technologies do these five big U.S. tech companies prefer? Both wind and solar, but so far mostly wind. Since 2010, they’ve bought more than five times as much wind as solar. The proportion may be changing, though. So far this year, 60 percent of their power buys have been solar.

Wind Before Sun

Technology company corporate procurement of clean energy

Source: Bloomberg New Energy Finance

Note: Megawatts recorded in year agreement was signed. Data as of May 23

Buying clean power can be relatively easy. In South Africa, however, things are a little complicated. In the U.S. and elsewhere, companies can simply buy clean energy from any utility that has a certification program ensuring the power comes from a zero-carbon source. Companies can also contract for power from an outside clean-energy source. But with South Africa’s utility, Eskom, there are obstacles.

South Africa has no renewable-energy certificate program, so the only way for Microsoft to guarantee clean power is to build its own source -- and that might not provide enough power to meet its demand.

Or the company could sign an agreement with an independent clean-power producer and pay Eskom a “wheeling” charge to deliver it, but Eskom hasn’t been signing any new power-purchase agreements.

That leaves buying power from Eskom itself, with no assurances that it comes from wind or solar. Eskom is an institution with a history of power blackouts, numerous scandals, and a less-than-stellar local reputation. In South Africa, it’s going to be a challenge for Microsoft to get clean power from a not-so-clean utility.

Weekend reads

• In a survey of 209 impact investors managing a total of $114 billion, 91 percent said that investments have met or exceeded their financial expectations.
• Two giant asset managers -- BlackRock and Vanguard -- may pressure Exxon Mobil to conduct a climate stress test “to measure how regulations to reduce greenhouse gases and new energy technologies could impact the value of its oil assets.”
• So-called “climate fiction” envisions New York City drowned by sea-level rise.
• Bloomberg’s Christopher Flavelle examines a bond market disconnect: Some New Jersey towns retain their AAA rating even as they are in danger of being wiped out by rising seas.
• Detroit’s new Public Lighting Authority built a streetlight network that’s clearly visible from space.
• A new poll Down Under shows that only 7 percent of Australians support spending public money on coal mines and coal infrastructure, while more than 60 percent support spending on renewable energy.
• A recent U.S. Census study found that more adults aged 18 to 34 now live at home with their parents than live with a spouse or partner.
• Self-driving vehicles have a significant “autonomous overhead,” due to the extra energy their sensors and processors use.
• A new study found few measurable social benefits from the use of solar lighting systems in India -- maybe because it observed only one hour of lighting.

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