The chip companies also know that they will definitely buy electricity in the future, yet they are not buying power plants.
In a sense, buying the future substrate production is just a future substrate contract.
Do you know how building a power plant is financed today? Basically someone buys 10 years of gas futures, sells 10 years of equivalent electricity futures, and uses the profit (since electricity is more expensive than gas) to build the power plant that will turn the bought gas into the sold electricity.