Don't forget to take into account that grid connected solar houses feed excess power produced into the grid, there's no free about it, these are essentially micro power stations which enhance the grid.
You're missing the point. The free part is they're selling back power at retail rates. In net metering if you generate as much power as you use you don't pay any per kWh charges. Where I live the power company is selling power to consumers for about 22 cents per kWh. From normal wholesale vendors it's buying power for somewhere around seven cents, but it's buying buying power from net metering people for 22 cents.
That's where the "using the grid for free" part comes in. People who purchase wholesale-generated power are paying the power company's overhead, whereas the net metering people aren't.
In addition, the home owners are selling a electricity at a fixed time and buying it back with flexibility, not taking into account the spot price of the electricity (which is going to lower drastically during peak solar times over the next few decades).
If every home owner installed sufficient solar power to be neutral under net metering, the grid would have to be maintained, with traditional generation supplied at off peak solar times at no cost to the home owner.
If that doesn't show how heavy a subsidy net metering is, I don't know what will. It's not sustainable and should never be used to price out solar.
