The underlying report, linked from the positivemoney.org site:
https://www.datocms-assets.com/132494/1776758395-pmeu-renewa...
Which says:
> We estimate that the deployment of wind and solar reduced wholesale electricity prices by an average of 24.2% over the period 2023–2025 across the countries analysed. These effects are nonlinear and increase with renewable penetration, reflecting stronger price impacts at higher levels of wind and solar deployment.
and
> ... over the 2023-2025 period in the sample of countries analysed, with large variation across countries.
(The pv-mag article also says these - 5th para.)
1 - I've no idea why pv-mag would use "Spain" in their headline. The report does not give a Spain-specific percentage.
2 - Pv-mag's headline also says "bills". While there's probably a positive correlation between wholesale electricity prices and Spanish end-user bills, the headline's implied "bills down 24.2%" is complete BS.