From 1 Jan 2019 the new capped standard tariff applies. SP have not altered the website yet, but it will probably be changed on 3/1/19 when everyone goes back to work.
The cap is £1137 a year for a typical user. Your actual cost will depend on how much power is used and could easily be higher than 1137. SP will have calculate new p/kWh rates for the standard tariff in order to hit the target level.
Enjoy the price reduction while it lasts and best wishes for 2019 to all.