To be a sole proprietor, one must run a BUSINESS. And if your business doesn't make any profits (because you set it up as a ruse to claim a Section 179 dedution), you'll have nothing against which to deduct the cost of the Model X, and therefore you will not save any money. Hence my original statement that this is a business deduction; not something available to individual taxpayers (i.e., "employed by someone else, not self-employed").
I agree that you have to run a "legitimate" business to take the Section 179 deduction. However, most American businesses have just one employee (the owner). And there are a lot of one person businesses that do turn a profit. Many of those businesses make money because they have little or no overhead or equipment, and they are just selling the owner's time and expertise. A good example is a pool man (cleaning & maintenance). They typically have a vehicle (pickup or SUV), a trailer, chemicals, and a computer and printer. A good pool man can make $50K to $80K of profit a year as a sole proprietor.
The $7,500 EV Tax Credit is a "Credit" - meaning it's a dollar for dollar reduction in Federal Taxes owed.
The Section 179 deduction is a "Deductible Business Expense" - The Federal Taxes saved depend on your tax bracket and the amount of the expense.
Here's a simple example for our Pool Man Sole Proprietor:
$100,000 - Sales Revenue
($30,000) - Business expenses
$70,000 - Gross Income
($25,000) - Section 179 Expense (from qualifying vehicle purchase)
$45,000 - Taxable Income
This Pool Man would be in the 25% Federal Tax Bracket (single filer) with or without the Section 179 Expense.
Since he reduced his taxable income by 25%, he saves $6,250 in taxes owed.
If the car was a plug-in EV, then presumably you could also take the $7,500 tax credit (if you owed that much in federal tax)
I still need to find out if you could actually take both the credit AND the deduction.