It has taken three years, during which time the technology and even the companies involved have changed, but the much anticipated SolarCity “gigafactory” in Buffalo, New York has finally produced its first PV cells.

This news was broken late last week by Associated Press, and reaffirmed by a statement by New York Governor Andrew Cuomo. Details are limited and it appears that so far this is only test production, as Tesla Chief Technology Officer J B Straubel told the Associated Press that ramp-of Tesla’s Solar Roof modules will begin “in a substantial way” by the end of 2017.

In September 2014, when SolarCity officially began construction of the plant, a statement by Governor Cuomo indicated that the factory could begin making modules as early as the first quarter of 2016.

But building the largest PV cell and module factory in the Western Hemisphere, using technology that has only been produced on a pilot scale, is not an easy or direct task. SolarCity was mum as that initial optimistic timeframe came and went.

The big changes came in late 2016. The factory was originally planned to make PV cells and modules based on Silevo’s high-efficiency technology, but as Tesla took over SolarCity, the company began making statements about “combining” Silevo’s technology with that of its long-time manufacturing partner Panasonic. This actually meant that Silevo would be replaced with Panasonic as the technology provider.

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Around the same time, Tesla began hinting that in addition to making standard PV modules, the new factory would produce a new Solar Roof product, with which Tesla CEO Elon Musk plans to bring back building-integrated photovoltaics in a new way. The first pilot Solar Roof tiles have already been manufactured at a smaller facility in Fremont and the first Solar Roofs have already been installed.

Either way, the state of New York is heavily invested in this project, which is located on the site of a former steel mill and is part of the state’s efforts to revitalize Buffalo. In fact, Tesla doesn’t even own the factory; but leases it from a non-profit associated with State University of New York.

These interests were reflected in New York Governor Cuomo’s statement on Friday. “The start of production at Tesla’s cutting edge solar plant by Panasonic is an exciting development for Buffalo and all of Western New York, and we look forward to seeing this factory play a growing role in the city’s economic transformation,” declared Governor Cuomo. “This is the first of many milestones to come, marking the launch of a world-class manufacturing hub that will continue to create jobs for New Yorkers and solidify New York’s role as a leader in the clean energy economy.”

And while Tesla expects that the plant will eventually ramp up to not only 1 but 2 GW of production, this is only the beginning. Elon Musk is already talking about the locations for future solar and battery gigafactories, based on the battery factory in Reno and the plant in Buffalo.