I can't say why some people on the coast have been able to get the discount offered by Iberdrola. What I can tell you, with a reasonable degree of certainty, is that it doesn't apply Pam and I.
The Social Rate was best described to me by the lady at Age Concern as being similar in principal to the Winter Fuel Allowance that some pensioners here receive from the UK government. Apparently it only applies to those in special circumstances and is more than a one off payment.
For the benefit of my Spanish readers, British pensioners here who lived in England on a particular date in September receive an allowance of £200 (£400 if they are over 80 years of age). The allowance is still paid to them even though they now live abroad.
However, for some inexplicable reason, those of us who moved to Spain before we reached pensionable age ar not eligible for the allowance. To get it, we would have to go back and live in England for that one week in September.