Anyone following Tesla Motors (NASDAQ:TSLA) stock closely is well aware of the fact that significant business growth over the long haul is absolutely crucial for investors to earn a meaningful return on their investment from here. Without rapidly growing its vehicle sales over the next five-plus years, Tesla will struggle to develop the economies of scale to begin reporting regular, meaningful profits. And without growth in the intrinsic value per share, the company could fail to live up to the stock's price valuation. On this note, can Tesla keep up its 50% plus year-over-year growth in 2016?

Tesla Vehicle Deliveries

Asterisk indicates estimate. Estimate for 2015 derived by adding the low-end of Tesla's fourth-quarter guidance range to its reported deliveries for the first three quarters of the year. Data for chart retrieved from Tesla's respective SEC filings for periods shown. Chart source: author

Looking back
It's still not exactly clear how many vehicles Tesla could deliver this year. But assuming Tesla can achieve the low end of its fourth-quarter guidance for 15,000 to 17,000 vehicles, the company will sell about 50,000 total vehicles in 2015. This represents 58% year-over-year growth.

During 2015, Tesla's vehicle sales growth will be almost entirely attributed to increasing sales of its Model S sedan. The company's Model X SUV, which was introduced at the end of Tesla's third quarter, is looking like it will represent no more than a few hundred of Tesla's 2015 vehicle sales.

Importantly, demand for the company's maturing Model S vehicle was still growing considerably toward the end of 2015. Management said in its third-quarter letter to shareholders that orders for Model S during Q3 increased "more than 50% from a year-ago, and grew at a faster pace in North America, Europe, and Asia, than during Q2." Management was also optimistic about China, saying orders in Q3 "increased substantially from Q2."

With this backdrop, how many vehicles could Tesla deliver in 2016?

Looking forward
Fortunately, Tesla has already provided a window into its expectations for 2016. Management noted in the third-quarter letter to shareholders that it was "highly confident of average production and deliveries of 1,600 to 1,800 vehicles per week for Model S and Model X combined during 2016." Assuming a few weeks of factory shutdowns for retooling, this would put total vehicle deliveries during 2016 around 80,000 if the company achieves the low end of its guidance.

Tesla Model X Delivery

Tesla delivers one of the first Model X vehicles. Image source: Tesla Motors.

But investors should take this outlook with a grain of salt. The company missed its initial guidance for 2014 and it is now planning to come in slightly below its initial guidance for 2015, which was for 55,000 vehicles. Notably, however, the company grew its sales significantly in both years -- just not quite up to par with its initial outlook.

With this in mind, what's a realistic expectation for Tesla's 2016 deliveries? Probably a figure closer to 75,000, which is about 10,000 off from the midpoint for its expected range of vehicle deliveries in 2016, and about 5,000 below the low end of its guidance.

Achieving 75,000 vehicle deliveries in 2016 would represent around 50% year-over-year growth over Tesla's expected 2015 deliveries. This growth rate would be slightly lower than Tesla's expected growth for 2015 of 58% and well ahead of its 2014 year-over-year growth of 41%.

Deviations from this possible scenario for growth in 2016 are not only possible but also likely. But Tesla investors should look for it to at least grow 2016 sales at a rate close to 50%, as execution for the company is critical; vehicle sales growth enables Tesla to move closer to the scale that will enable it to economically build and sell its lower-cost Model 3, which is slated for a late 2017 launch.

Daniel Sparks owns shares of Tesla Motors. The Motley Fool owns shares of and recommends Tesla Motors. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.