Since I "use it at my house" and "would not have purchased it" without owning and operating a PHEV, doesn't that make it free (of course only after applying your condition about forgetting installation costs).
No, it doesn't.
Let's say that your monthly consumption, by all your load, except the PHEV is 1500kWh and your PV produces 1000kWh. Also, assume that electricity price charged by the utility is $0.10/kWh. (numbers are random, I just want to use nice round figures)
Your net-meter at the end of the month will show 500kWh (1500-1000) consumed from the grid and your payment would be $50 (500kWh * 0.1$/kWh).
Let's now assume that you also charge your PHEV and you use 300kWh during the month for that purpose. In this case at the end of the month your net-meter would show 800kWh (1500+300-1000) and you would pay $80. That difference of $30 is cost of charging your PHEV, with price $0.10/kWh ($30/300kWh).
On the other hand, if your PV produce more than your total (PHEV excluded) consumption, PHEV charging would be cheaper or even free.
For the same example as above, let's now assume that your PV production during the month is 1700kWh, with everything else the same. At the end of the month, if you don't charge PHEV, your net meter would show -200kWh (1500-1700). Assuming that the utility doesn't pay you for "negative" energy, your bill would be $0.
Let's now assume that you charge PHEV and use 300kWh for that. Your net-meter would show 100kWh (1500+300-1700) and your bill would be $10. That $10 is cost of charging your PHEV, with price $0.033/kWh ($10/300kWh).
Now, if your PV produces 2000kW during the month, your net meter would show -500kWh if you don't charge PV , or -200kWh if you do. In both cases your bill would be $0 and your PV charging would be free.
Therefore if your PV production surplus is more that what you need to charge PHEV, the charging is free. If you have PV production surplus, but less that what you need to charge PV, the cost of charging would be more than 0, but less that utility price.
If your PV can not cover complete consumption (excluding PHEV), the price of charging the PHEV is the same as the price your utility charges you.