@Panda
Time for an analogy:
Suppose your workplace has this scheme under which you are getting partially reimbursed for your fuel cost. There's a mandatory prerequisite, though. You've to buy the fuel from a specific outlet at the rate set by your employer (who happens to be the owner of the fuel outlet as well), no matter what the price is in the market.
A friend of yours has a mini fossil fuel power station and offers you to utilize the surplus fuel at a substantially low rate than the retail outlet. Now, it is indeed a worthy proposal since you can save more, even compared to the reimbursement you get from your workplace. The only catch is you can't submit the receipt to your employer, cause that would be considered as a loophole. You can, however, still get benefitted if you restrict your friend's offer to personal usage.
At the end of the day, what you're getting is the same fuel with identical quality parameters, but the associated restrictions are different.
That's all.