To put this in context as well, most places (at the least in the southern parts of Spain) don't have central heating systems or proper insulation. A fireplace or reversible A/C if you're lucky.
Most places in Spain have and need heating, apart from a few coastal enclaves in the south. Spain is the 5th largest user of energy for residential heating in the EU, behind Germany, France, Italy, and Poland.
I did a quick search for more objective observations and what I found was:
Homes labelled A, B and C account for less than 10% of the housing stock. […] Most of households in the sample (52%) are E rated. F and G rated residences account for almost 25% of the sample. [1][2]
In Spain, buildings are currently responsible for 31% of energy consumption. […] the classification A - the highest - involves spending up to 10 times less than the G - the lowest -. Currently, in Spain most buildings have an E, F or G rating.[3]
[1] https://www.sciencedirect.com/science/article/pii/S030142151... (4. Results and discussion)
[2] https://en.wikipedia.org/wiki/European_Union_energy_label
[3] https://www.interregeurope.eu/enerselves/news/news-article/2...