provided, you're paying a net of $1600 for electricity ($2000 paid to Tesla less $400 received). Based on your estimate of $400 received at $.027/kWh sold, you have sold somewhat less than 15000 kWh. If you use 10% of the generated electricity, you're using ~1600 kWh. If you bought the electricity directly, it would cost you 1600*.23 = <$400. It seems to me that you should cancel your contract and have Tesla remove the solar cells.
Would that I could. I had to assume the solar contract signed by the previous owners, and it provides that the contract can only be canceled by buying it out, basically for the net present value of all the money Tesla expects to get until year 20, i.e. for the next 16 years.