There are two parts of this problem:

1. If you are connected to the grid and using it you need to pay for it somehow. This is not a capitalisim thing this is a maintenance issue. Deploying lots of rooftop solar reduces the amount people are paying the grid operators for the same infrastructure as before while they are still using it. This could be solved by making the grid operators public utilities again and charging taxes instead of billing electric rates. Either way rooftop solar owners are going to need to pay grid fees unless they are entirely disconnected from the grid (this is rarely ever the case).
2. It creates issues where generation may outstrip load as well as transmission and storage capacity. A lot of this can be solved with more investment but if you are earning less of power sales and still need to maintain everything this can be financially challenging.

There is also a third problem where home solar isn't centrally planned resulting in cases where utilities need to delay homeowners' solar installations while they figure out grid capacity.

How can the price go negative? There's always going to be maintenance costs that have to be covered if nothing else.

Won't someone PLEASE think of the prices?!

𝖸𝖾𝖺𝗁 𝗌𝗈𝗅𝖺𝗋 𝖼𝖺𝗇’𝗍 𝖻𝖾 𝖺 𝗆𝗈𝗇𝗈𝗉𝗈𝗅𝗒 𝖻𝖾𝖼𝖺𝗎𝗌𝖾 𝖢𝗁𝗂𝗇𝖺 𝖺𝗅𝗋𝖾𝖺𝖽𝗒 𝖼𝗈𝗇𝗍𝗋𝗈𝗅𝗌 𝟫𝟢% 𝗈𝖿 𝗍𝗁𝖾 𝗉𝖺𝗇𝖾𝗅𝗌 𝖺𝗇𝖽 𝗍𝗁𝖾 𝗆𝖺𝗋𝗀𝗂𝗇𝗌 𝖺𝗋𝖾 𝗌𝗈 𝗋𝖺𝗓𝗈𝗋 𝗍𝗁𝗂𝗇 𝗍𝗁𝖺𝗍 𝖶𝖾𝗌𝗍𝖾𝗋𝗇 𝖼𝗈𝗆𝗉𝖺𝗇𝗂𝖾𝗌 𝖼𝖺𝗇’𝗍 𝗆𝖺𝗄𝖾 𝖻𝖺𝗇𝗄 𝗈𝗇 𝗍𝗁𝖾 𝗁𝖺𝗋𝖽𝗐𝖺𝗋𝖾. 𝖨𝗇𝗌𝗍𝖾𝖺𝖽 𝗍𝗁𝖾𝗒 𝗁𝖺𝖽 𝗍𝗈 𝗀𝖾𝗍 𝖼𝗋𝖾𝖺𝗍𝗂𝗏𝖾 𝖺𝗇𝖽 𝗌𝗍𝖺𝗋𝗍 𝗅𝖾𝖺𝗌𝗂𝗇𝗀 𝗍𝗁𝖾 𝗌𝗁𝗂𝗍 𝗈𝗋 𝗌𝖾𝗅𝗅𝗂𝗇𝗀 𝗒𝗈𝗎 𝖺 𝖻𝖺𝗍𝗍𝖾𝗋𝗒 𝗐𝖺𝗅𝗅 𝗃𝗎𝗌𝗍 𝗍𝗈 𝗅𝗈𝖼𝗄 𝗒𝗈𝗎 𝗂𝗇. 𝖠𝗇𝖽 𝖾𝗏𝖾𝗇 𝗍𝗁𝖾𝗇 𝗒𝗈𝗎 𝗌𝗍𝗂𝗅𝗅 𝖼𝖺𝗇’𝗍 𝗌𝖼𝖺𝗅𝖾 𝖿𝖺𝗌𝗍 𝖻𝖾𝖼𝖺𝗎𝗌𝖾 𝗍𝗁𝖾 𝗀𝗋𝗂𝖽 𝗂𝗌 𝖺 𝟣𝟫𝗍𝗁 𝖼𝖾𝗇𝗍𝗎𝗋𝗒 𝗋𝖾𝗅𝗂𝖼 𝗍𝗁𝖺𝗍 𝖼𝖺𝗇’𝗍 𝗁𝖺𝗇𝖽𝗅𝖾 𝗍𝗁𝖾 𝗏𝗈𝗅𝗎𝗆𝖾 𝖺𝗇𝗒𝗐𝖺𝗒.

They've found the same is true for the wind, that the oil robbers can't own that either... I think Maria may own the wind... I'm not sure. They call it that... the wind, that is.