The cost of the sun is always the same: zero. Even when you take the cost of the facilities into account, large-scale solar thermal installations will generate the lowest possible heating costs. Hence, it will stabilize the price of your heating on a low level. While the cost of fossil fuel energy is fluctuating (and rising over a long-term period), the price of solar thermal energy is fixed. And you will know all costs from the start, meaning that the price of a MWh can be fixed over a 25-year period. That is independence!