As far as deliveries go, electric-car maker Tesla Motors (NASDAQ:TSLA) crushed it last quarter. Deliveries were up 114% year over year and 72% sequentially. But despite the recent rapid growth, Tesla's guidance for the final quarter of the year suggested management only anticipated a modest hike in unit sales. The company said it expects deliveries to be just over 25,000 units, or only a few hundred units higher than in its third quarter. Could this guidance be overly conservative?

Model X production at Tesla's factory in Fremont, California. Image source: The Motley Fool.

There are three catalysts for continued growth in Tesla's deliveries that could boost deliveries higher than management forecast.

1. Self-driving hardware

Just one week before Tesla posted its third-quarter results and shared guidance for its fourth quarter, the company surprisingly announced it had begun shipping every vehicle with sensors for fully autonomous driving.

While software updates enabling these new vehicles to start driving themselves could be years away in many of Tesla's markets, as the company refines the system and waits for regulatory approval, the significance of this update shouldn't be overlooked. The new sensor suite includes 360-degree visibility around the car up to 250 meters, 12 improved ultrasonic sensors to supplement its cameras, and forward-facing radar. And these sensors are powered by a new onboard computer with over 40 times the computing power of the previous-generation processor in Tesla vehicles.

Fortunately, Tesla isn't making buyers wait until the self-driving update is ready to begin letting customers benefit from these sensors. Customers who buy these vehicles with the updated sensor suite can purchase what Tesla calls its "Enhanced Autopilot," or essentially an improved version of its existing driver-assist Autopilot system. Tesla plans to begin rolling out its software updates for its enhanced autopilot as soon as the company has enough data from updated vehicles on the road to calibrate the new sensor suite.

Throughout the quarter, Tesla has been prominently marketing the inclusion of self-driving sensors in every vehicle by highlighting the feature on its homepage and linking to a video showing the feature in action.

2. Model S and X updates

During the fourth quarter, Tesla also announced a few notable upgrades to its Model S and Model X.

The Model X (left) and Model S. Image source: The Motley Fool.

For its Model S, Tesla added an option for an all-glass roof. The new upgrade option no longer includes a center crossbar, creating a long seamless piece of glass across the top of the vehicle.

And Tesla's new Model X option is perhaps even more notable. The company finally began offering a seating option with a foldable second row. The feature helps create 88 cubic feet of interior cargo space, giving the SUV the greatest interior storage capacity of its class, according to Tesla. Not having an option for foldable second-row seats was one of the biggest complaints about the Model X.

These updates were announced in the beginning of November, leaving enough time for customers to place orders for vehicles with these new options and still take delivery before the fourth quarter ends.

3. Increasing production

Finally, rising production during Tesla's fourth quarter should make it easier for the company to deliver more vehicles than its guidance for "just over 25,000 units" calls for. Barring any unexpected bottlenecks in Tesla's factory, it's likely the company continued to increase production during the final quarter of the year.

Tesla factory. Image source: The Motley Fool.

In Tesla's third-quarter shareholder letter, management specifically noted it was still ramping up production of its Model X. While Tesla management has repeatedly emphasized how difficult it is to predict the SUV's production ramp-up, it has certainly been very rapid recently. Thanks to rising production of the vehicle, third-quarter Model X deliveries jumped 89% sequentially. While Tesla's conservative guidance for total vehicle deliveries obviously suggests investors shouldn't expect such a sharp increase in Model X deliveries in Q4, it's unlikely the continued production ramp-up for Model X won't lead to at least slightly higher deliveries during the quarter.

These three catalysts combined should make it fairly easy for Tesla to beat its own guidance for vehicle deliveries in the final quarter of the year. The company has beat its quarterly guidance for vehicle deliveries in 11 of the past 14 quarters, but has missed its guidance twice this year. Tesla announces vehicle deliveries within three days of each quarter's end, so investors can expect an update on the key metric during the first three days of January.