Natural gas, from the Slochteren gas field, was the cheapest way to heat a home for the past 60 years. It's probably not so anymore, considering the Slochteren field is mostly shut down.
The city heating network operator is a monopoly, that is why the price is capped.
Even though city heating networks utilize 'waste heat', the capital cost of the network is significant. The price cap and the capital costs (especially now with higher interest rates) led to many proposed projects being cancelled in recent years.
But if you had been wrong and we would now have had superintelligence, the upside for its owners would presumably be great.
... Or at least that's the hypothesis. As a matter of fact intelligence is only somewhat useful in the real world :-)