Renewable Energy
They are two different things. Under a PPA, a user signs an energy purchase contract with the SPV and pays for the energy they consume: they own nothing. By subscribing shares, an investor becomes a shareholder of the company that owns the solar system and shares in the project's profits.
Example: in the same project, the host user signs the PPA with the SPV, and the investor subscribes shares in that SPV. Two different counterparties to the same asset.