We already know Alexa had a good Christmas — the app shot to the top of the App Store over the holidays, and the Alexa service even briefly crashed from all the new users. But Alexa, along with other smart speaker devices like Google Home, didn’t just have a good holiday — they had a great year, too. The smart speaker market reached critical mass in 2018, with around 41 percent of U.S. consumers now owning a voice-activated speaker, up from 21.5 percent in 2017.

According to a series of reports from RBC Capital Markets analysts released in December, the near doubling of the adoption rate for smart speakers in the U.S. was driven by growth in both Alexa and Google Home devices, while Apple’s HomePod played only a small role.

The firm found that U.S. penetration of Alexa-enabled devices reached 31 percent this year, compared with 41 percent overall for smart speakers.

It also forecast that Alexa would generate $18 billion to $19 billion in total revenue by 2021 — or ~5 percent of Amazon’s revenue — through a combination of device sales, incremental voice shopping sales and other platform revenues. In the U.S., there are now more than 100 million Alexa-enabled devices installed — a key milestone for Alexa to become a “critical mass platform,” the report noted.

RBC additionally called out Amazon’s progress with Alexa’s development, with launches like Alexa Guard, which listens for break-ins and smoke detector alarms; plus new features like local voice control for when the internet is down; location-based reminders; advanced routines; email integrations; expanded calling options; and many others.

Alexa’s third-party app ecosystem also grew in 2018, with 150 percent year-over-year growth in skills to reach over 60,000 total Alexa skills by year-end. That’s up from 40,000 skills in May; 25,000 in Q3 2017; and just 5,000 two years ago.

Google Home also gained traction in 2018, with U.S. penetration for Google devices growing to 23 percent, up from 8 percent in 2017. Each household owns around 1.7 devices, which leads a Google Home install base of around 43 million in the U.S., and around 9 million in other Google Home markets, the forecast said.

However, the report doesn’t see as much revenue coming in from Google Home over the next few years, compared with Alexa. Instead, it estimates that Google Home generated $3.4 billion in revenue this year, and will grow that to $8.2 billion by 2021.

But combined with Google’s other hardware products like Pixel, Nest and Chromecast, the hardware suite will have generated approximately $8.8 billion in 2018, and will grow to $19.6 billion in 2021.

This is the first year the analysts asked about Apple’s HomePod in the consumer survey, and they found its share of the U.S. smart speaker market remains small. Amazon has a 66 percent share to Google’s 29 percent. HomePod had 5 percent, it said.