Image source: Tesla.

There's no shortage of important strategic questions as we approach Tesla's (TSLA -3.55%) Model 3 unveiling event at month's end. What battery capacity will the vehicle have? What standard features will be included? What does it even look like?

In the feature department, perhaps the most important one beyond what a range/capacity upgrade will cost is whether or not Supercharging will be included.

Expect to pay extra
I fully expect that Supercharging will not be standard on the Model 3. The vehicle should include the necessary hardware, but more than likely customers will need to pay extra to activate the ability to Supercharge.

You may recall that Tesla initially had the same strategy for the lower end 40 kWh and 60 kWh trims of the Model S when it first launched. Customers could activate Supercharging for $2,000 when ordering their car, or $2,500 after the fact. But given the low popularity of the 40 kWh models, Tesla quickly killed that capacity, and then shortly thereafter made Supercharging a standard feature for all Model S vehicles, saying that the capability was simply built in to the price of the car.

It's hard to imagine that Supercharging will be built-in to the price of the $35,000 Model 3, and it's an easy upsell that will help boost Tesla's average transaction price. While the cost of Supercharging hardware inside the vehicle is likely modest, the real cost comes from building and expanding the Supercharger network.

A long and winding road
As of the end of December 2015, Tesla had a total of 584 Supercharger stations globally throughout North America, Europe, and Asia, with plans to continue expanding. The carrying value of these Superchargers net of depreciation was about $167 million (Tesla overstated the carrying value in its recent 10-K but subsequently corrected it, citing "an immaterial error"). Each station costs a few hundred thousand dollars to build.

Planned North American Supercharger network by the end of 2016. Image source: Tesla.

In addition, it's possible that not everyone would need Supercharging. If you only drive locally and don't really take road trips, you don't really need the Supercharging option, particularly if it costs extra. On top of that, the network may not be able to handle the volumes that Tesla is shooting for, in which case charging extra will also limit congestion. Some areas like California that have a lot of Teslas on the road have experienced Supercharger congestion at times, particularly around busy travel times like the holidays. Tesla has also asked customers to not charge locally if they live nearby, since Superchargers are primarily intended for long-distance travel.

How much could it cost? $10?
Tesla still offers the $2,500 Supercharging separate option on its site, but this figure seems like it might be a bit high for a $35,000 Model 3. Especially since the Supercharging cost curve, including development and hardware, has likely fallen. More importantly, fuel savings is very likely to be an important factor for this market segment, unlike the luxury vehicle segment, and $2,500 is easily several years worth of gas.

Considering the volume goals for Model 3, Tesla can also scale the Supercharger buildout costs over a larger base, which would allow it to charge less per unit and still help fund the expansion. My guess is that it will cost $1,000 to $1,500 extra. The option should be less than it used to cost ($2,000) but still enough to raise capital for infrastructure while gating congestion. If Tesla upsold 100,000 units at $1,000 a pop over the first year, that $100 million would go a long way towards expanding the Supercharger network.

Now, if Tesla wanted to be really aggressive, it certainly could include it for free and watch demand skyrocket. But I don't think it will do that.