Thanks for breaking it down to make it easily understandable for the uninformed. The 15 month period you refer to is the absolute minimum that the tax credit will be valid. More likely, it will stretch out to 18 months, since Tesla will have the capability of manipulating production and delivery. For example, if the 200,000th car is delivered on 1/1/18, the full credit will be valid for the remainder of that quarter, 3/31/18, as well as the following quarter ending 6/30/18. Then, there will 6 months of 50% credit, followed by 6 months of 25% credit.
Assuming that 1/1/18 is the date for the magical 200,000th car, the credit slate will look like this:
1/1/18 - 6/30/18 = 100% tax credit ($7,500)
7/1/18 - 12/31/18 = 50% tax credit ($3,750)
1/1/19 - 6/30/19 = 25% tax credit ($1,875)
Total of 18 months
If the unthinkable happens and the 200,000th car is delivered on 12/31/17 (just one day earlier), we would lose essentially 3 months of full credits. It would then look like this:
12/31/17 - 3/31/18 = 100% tax credit ($7,500)
4/1/18 - 9/30/18 = 50% tax credit ($3,750)
10/1/18 - 3/31/19 = 25% tax credit ($1,875)
Total of 15 months
I'm sure that Tesla will "manage" production so that the 200,000th car will end up closer to the first scenario, rather than the second.
I hope your right on your estimates, but to me, it seems like there will be very few, if any Model 3 owners that will get the full tax credit. I could be completely off base, so feel free to shoot down my numbers if they're incorrect:
As of the end of 2015, there have been almost 107,000 Tesla's delivered (2658 in 2012, 22,450 in 2013, 31,655 in 2014 and just over 50k in 2015). That means they only need to sell 93k more cars to hit that threshold. 2016 guidance has them delivering 100k.
Elon is a man of his word, so lets assume that he'll hold off delivering the 200,000 car until 1/1/17 (which would make them lose out on about 7k sales in forth quarter of 2016), the schedule looks more like this:
1/1/17 - 6/30/17 = 100% tax credit ($7500) - however, no Model 3 owners would get this
7/1/17 - 12/31/17 = 50% tax credit ($3750) - The very first Model 3 owners would get this
1/1/18 - 6/30/18 = 25% tax credit ($1875)
So, if we break this down, the factory where these will be made, at full scale, should be able to pump out 500,000 cars a year (though, some have said that's a high estimate). They'll likely only be at 20-40% capacity when they first start rolling cars out, so I think a fair guess would be about 7k Model 3 deliveries in the final quarter of 2017 (50% tax credit). If they make it to full capacity by the start of 2018 (which is probably unlikely), they would be able to pump out about 41k cars a month, so would be able to deliver 246k cars at the 25% tax credit.
Like I said, my numbers could be off - so feel free to correct me, but I don't think people shouldn't be making this purchase solely based on getting the full, or even half, of the tax credit (I think it's just an amazing car, so will be happy to fork over the full amount).