Nintendo Switch Online launches tomorrow, September 18, so going forward you'll need to subscribe to the service if you want to play Switch games like Splatoon 2 and Mario Kart 8 Deluxe online (though Fortnite does not require a subscription). Luckily, as the service's official FAQ explains, you can purchase a subscription using Nintendo gold points earned via purchases in the eShop.
One gold point is worth $0.01, so you can use 300 points to purchase a $3 eShop item. As we explained in our Switch Online breakdown, one month of the service costs $4, three months costs $8, and a year's subscription costs $20. So, you'd need 400, 800 and 2,000 points respectively. The yearly subscription is the best deal, so we'll focus on it.
You earn points on most Switch, 3DS and Wii U game purchases, but the system is heavily skewed toward digital games. If you buy games through the eShop, you earn points worth five percent of your purchase. So a new, $60 digital game would get you 300 points. But for physical games, you only earn points worth one percent of that game's digital price, meaning a hard copy of the same $60 game would get you 60 points.
In other words, to pay for a Switch Online subscription using gold points alone, you'd need to spend at least $400 in the eShop every year, provided you purchase a yearly subscription. Otherwise you'd need to spend $80 every month or $160 every three months. You may also be able to partially cover your subscription using whatever points you have.
Note that any Switch Online subscription purchased using gold points will not automatically renew, and the points themselves expire one year after you acquire them. Unfortunately, you won't earn points when you purchase a subscription normally.
Wondering what games you might want to buy in the eShop? Check out our list of the best upcoming Switch games.