I think there's a lot of currently unknown factors involved, for a lot of things we'll reach a point where the technology is evolved to a point much more efficient than current solutions. It's possible as well that these systems will make effective use of small cycles so we're only having to put very small amounts of extra energy into it to maintain the cycle.

Automated construction tools could for example make it very cheap to install grey water systems and water filtration which greatly reduce the demand on our current supply and sewer systems. Likewise with TV, we currently have big screens but a small headband that interacts with the optic nerve or brain might be far more efficient. If most houses can generate the power they need locally then huge parts of the electrical grid could be removed which would save huge amounts of power.

I think we'll always want to do big projects and use more power for science and community growth but hopefully a lot of that can be done in space or areas that are especially well suited such as deserts or floating platforms in the ocean where room and power are cheap.