Suppose x is the kwh you are going to use to charge your car over the years, 10 cents per kwh at home and 40 cents per kwh at a charging station. To break even, you need to have
0.1x + 2000 = 0.4x (2000 is the cost of installing a 240v outlet and/or a charging device)
Solving this equation gives you: x = 6666 kwh.
This translates to 17777 miles (6666 / 78 * 208).
So if you are sure you will charge your car AT HOME for range at least of 17777 miles, then installing a 240v outlet would make sense financially.
Keep in mind you can only charge your car at home for normal things such as commuting, routine shopping, etc. (no road trip).
For me, I work from home 5 days a week, and a weekly shopping trip is usually 30 - 50 miles. Let's say weekly you will drive 100 miles, then annually 5200 miles (on your home charge).
17777 miles would be about 3.42 years. That's around year 2024-2025. There could be some new technology out then, so your current charging device might look like an antique.
Again in my case, even I intend to charge mostly at home, I do NOT need a 240v outlet because the car can be fully recharged in about 2-3 days using a 110v outlet. So it won't prevent me from doing my weekly shopping. Furthermore, keep in mind that you do NOT need a full battery to drive the car. 50% charge (1 - 2days charging at a 110v outlet) already can give you about 100 mile range. More than enough to do some ad hoc shopping trip, etc. And if I do need a long trip, I can take advantage of a nearby fast charging station in case my car is not yet fully charged.
So unless you actually commute daily and/or fast charging station is really far away, it would be making no sense to install a 240v outlet at home for $2000 in my opinion.
