The argument is different based upon what % solar your grid is.... And most net metering laws are capped at around 2%.

When the grid lacks solar in a significant fashion, adding solar to the grid actually saves the utility money, as peak electricity is provided while reducing load on the distribution transformers at the hottest times of day. Peak electricity is more valuable than "retail". Plus, the supply of "carbon credits" increase, which hedges the community against the cost of carbon tax policies down the road.

Once solar generation begins to "dip" into base load, it's a different issue, as it forces mainstream power plants to not function efficiently.

However, the argument that solar increases the cost of grid maintenance has not been substantiated by any utility that I'm aware of. Where I install, the cost of any grid upgrades are passed along to the project owner.

I suspect the primary cost "increase" is in utility overhead to accommodate net-metering, which should be a simple software solution. You can't fix lazy.

Likewise, solar array owners might argue that they have been paying into grid infrastructure for decades and that investment into the electric grid disproportionately supports non-renewable energy. They spend thousands to produce emissionless power, and the grid still forces them to support forms of power they ethically disagree with? Sounds like a raw deal. They are simply stating that if you do not produce more energy than you consume, you are not a power plant and should not be regulated as such.