Elon MuskREUTERS/Danny MoloshokTesla CEO Elon Musk.
Tesla just released in fourth-quarter and full-year 2015 delivery numbers.
The automaker sold 17,400 vehicles in Q4: 17,192 were Model S sedans and 208 were Model X SUVs, the company said in a statement.
In 2015, total deliveries were 50,580, the most ever for Elon Musk's electric-car startup, but on the low side of the 50,000-55,000 guidance that the company provided in the middle of last year.
At the beginning of 2015, Musk said that that Tesla would deliver 55,000 vehicles, but the company later trimmed that back. 
In 2014, Tesla managed to build a predicted 35,000 cars, but was unable to deliver them all in the calendar year, with some deliveries slipping into early 2015. 
Deliveries have been a closely watched data point for analysts covering Tesla, as well as much of the media. Musk has consistently said that Tesla doesn't have any issues with demand for its vehicles, but rather is constrained in how many it can produce. 
However, from the CEO's perspective, Tesla needs to come close to consistently meeting expectations on production and delivery targets, to avoid making customers who have put down deposits wait for their cars and assure investors that the company, with a market cap of around $30 billion, can achieve its goal of building 500,000 vehicles annually by 2020.
In the past few weeks, Tesla observers have expressed the expectation that the automaker would make the low end of its guidance.
Tesla provided a modest amount of commentary on the numbers in a short press release:
Q4 Model S deliveries were approximately 48% more than our prior quarterly record and approximately 75% more than Q4 last year. Model X deliveries are in line with the very early stages of our Model X production ramp as we prioritize quality above all else. That ramp has been increasing exponentially, with the daily production rate in the last week of the year tracking to production of 238 Model X vehicles per week. 
There may be small changes to this delivery count (usually well under 1%), as Tesla only counts a delivery if it is transferred to the end customer and all paperwork is correct.
Our vehicle deliveries represent only one measure of our financial performance and should not be relied on as an indicator of our quarterly financial results, which depend on a variety of factors, including the cost of sales, foreign exchange movements and mix of directly leased vehicles.

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