If Tesla Motors (NASDAQ:TSLA) posts its quarterly deliveries within three days of the quarter's end, as the company has promised, investors should know how many vehicles the electric-car maker delivered during Q4 by the end of this weekend. Here's what investors should consider before the numbers are released.

Tesla Fremont factory. Image source: Tesla Motors.

Growth in Q4 will be huge
Based on Tesla's quarterly guidance, the company is expecting some incredible sales growth during the final quarter of the year. Management said in Tesla's third-quarter shareholder letter it is expecting to deliver between 17,000 to 19,000 vehicles during the quarter. This represents 73% to 93% year-over-year growth and 47% to 64% sequential growth.

But full-year deliveries will fall short of initial expectations
While the growth Tesla is expecting in Q4 is quite astounding, it's worth noting that management's expectations for the quarter actually put the company below its initial guidance for the year.

Going into 2015, Tesla expected to deliver about 55,000 Model S and X vehicles. But, as Tesla's timeline for the first Model X deliveries slipped about one and a half to two months, its full-year guidance was changed during the Q2 to reflect this delay. The guidance was adjusted to a range of 50,000 to 55,000 vehicles. And this range narrowed even further when the company reduced its expectations for full-year deliveries to 50,000 to 52,000 vehicles in its third-quarter shareholder letter.

Of course, 50,000 to 52,000 vehicles for the full year still represents enormous growth for the company. Even the bottom end of this narrowed range for full-year vehicles represents about 58% year-over-year growth in deliveries compared to 2014. Furthermore, this would represent a significant acceleration from Tesla's year-over-year growth of 41% between 2013 and 2014.

Model X could drag deliveries lower or drive them higher
Tesla's wide range of expected deliveries during the quarter is due to the uncertainty associated with ramping Model X production.

Tesla Model X delivery during the launch event for the vehicle. Image source: Tesla Motors.

"Model S production and deliveries are on track to achieve our initial Q4 plan," Tesla said during the company's third-quarter shareholder letter. "The primary limiting factor to higher Q4 deliveries is the near term ramp of Model X production, with the biggest constraint being the supply of components related to the second row monopost seats."

The letter went on to explain that the company had taken over production of the monopost seats -- a job Tesla had initially outsourced -- in order to address this bottleneck.

During the company's third-quarter conference call, management provided more insight into the uncertainty surrounding the initial ramp-up of Model X production. A shift of even a week or two earlier or later on an exponential curve of the ramp-up in deliveries of Model X could hold back or propel deliveries, respectively, by significant amounts, management explained.

While Tesla is unlikely to break down its reported quarterly deliveries this weekend by model, it's likely that a number closer to 19,000 implies the Model X production ramp-up during the quarter was at the high end of the company's expectations and a number closer to 17,000 suggests the ramp-up was at the low end of expectations.

Tesla should post fourth-quarter deliveries before Monday. Stay tuned at The Motley Fool for a closer look at the numbers and what they mean.