npower capped prices for current customers

I've gone for this. I was on the Sign-up OnLine 6 economy 7 tariff and they moved me to the standard E7 rate fixed until March 2009. I've calculated that I will pay 19% more per month until the end of the deal. Whether it's worth doing or not depends when, and by how much, they increase their tariffs. For example, if they don't put up the tariffs until next January, it would have to increase by 85% before I would be better off taking the fixed tariff. I'm having second thoughts now!