In the UK, we have a similar system, and for a decent time it actually did deliver low energy prices for us. The way this worked was that a new energy provider could easily set up and offer low tariffs, backed by private investment and a gamble that long-term prices would stay low. Of course, when prices rose, that gamble failed... and who picked up the bill? Why, the taxpayer, of course! [1]
The overall effect of this game was that more astute consumers, who tended to switch to the lower-cost providers, were ultimately subsidised by the less-astute consumers who stuck with the traditional players. Or to put it another way, the rich were subsidised by the poor.
[1] https://www.bbc.co.uk/news/business-63805028
