Tesla added 15,000 charges in the past 18 months. Electrify America (EA) plans on having a total of 3,500 fast DC chargers in their network by the end of the year. So right now they are growing the supercharger network at a rate of 1 EA per quarter.
I don’t quite get how that meshes with the idea that their lead is shrinking.
You are using incorrect numbers. Tesla claims to have 25,000 superchargers (connectors)
world-wide today, and this is Tesla, so they might be counting ones in boxes in some warehouse (see prior Tesla claims like driverless FSD is ready and only pending validation and regulation in 2016, or how they compared P85D horsepower, etc). But, for this argument let's assume the 25,000 is correct and counting live Tesla DC chargers around the world.
Second, you cannot use Tesla world wide numbers. EA is USA only, so you cannot compare world-wide chargers to USA chargers only. From
wikipedia:
As of March 2020, Tesla operates 16,103 Superchargers in 1,826 stations worldwide;
[25] these include 908 stations in the U.S., 98 in Canada, 16 in Mexico, 520 in Europe, and 398 in the Asia/Pacific region.
[3] Tesla reports 908 total supercharging stations in the USA today. I couldn't find the number of
So, that's just shy of half the supercharging stations in the USA, so let's assume 12,500 connectors for simplicity. That is not as rosy of a picture as you say when comparing to 3,500 EA connectors. EA deployed their first 3,000 connectors much quicker than it took Tesla to do their first 3,000 connectors, and their connectors are faster (up to 350KW) and don't share power as often as Teslas (all supercharger v2 has shared A/B power), so total charging capacity in KW comparison looks even less rosy. Also notice that EA is also not the only fast charging network in the USA, others are here and expanding too. If you are going to judge Tesla's lead in DC charging, you must include all of the competition, not just the leader. The competition is also interoperable, meaning competition cars can charge on any of their networks, not tied to EA. Competition, especially EA has had a bunch of early deployment issues, most of them stemming from lack of standardization and the fact that they are a consortium so operate like a democracy vs, Tesla dictatorship by Elon, which has a lot of advantages in situations like that. However, the plug-and-charge standard is finally here, and car companies are signing on to use it, meaning it will work like with Tesla superchargers, you plug-in and your account gets billed.
If the government passes their $3.5T infrastructure spending bill, Tesla competition will be expanding even faster, while Tesla will only get a piece of it if they open their superchargers to other manufacturers (I hope the politicians write it properly so Tesla doesn't get that money by opening only one or a handful of superchargers, like they got the grant for deploying battery swap technology and got away with deploying only one and for limited customers only).
My guess is the total number of CCS connectors in the USA will pass number of Tesla supercharger connectors in the next 3-5 years max. But that is just my guess about the future. The facts is Tesla went from having no competition, to ever growing number of competing DC charging connectors, so their lead is absolutely shrinking.