Mynewt:Unless Scottish Power have significantly reduced their prices recently, only a very few customer's will actually be able to save money with Scottish Power over other provider's, even factoring in the cash back
A random check on two supply regions and a couple of consumption profiles has Scottish Power now on top on the 4 comparisons I tried. I assume that's because of the cashback but sadly I don't think that's 100% clear from the use of the term "+ £40 cashback" in the result.
I'd prefer to highlight something else. Most of the current top rated tariffs feature "guaranteed discount against standard tariff". In some cases the "guarantee" (though not the initial saving) is as little as 2% for which dubious benefit "lock-in" applies for the tariff period. That's a potentially "worthless" guarantee if you believe rates are going to increase.
There are one or two "genuine" fixed rates in the top few. Up to customers to do their own comparison and choose, taking acount of all factors, headline price, cashback and tariff small print.