A lovely little quote lifted from BSI-014 "Deciding on Energy Priorities when Building New" from Buildingscience.com
Hence, if you doubt energy prices are going to triple over the next 25 years, and have a hunch that PVs will soon get cheap enough to compete with grid-supplied coal power, you might choose to skip the ground-source heat pump, R75 attic insulation and R25 basement insulation, HRV, and LED lights in your next house design. If your hunch is wrong, and energy prices double over the next ten years, or if natural gas becomes very expensive, the owner has a number of significant, low-cost, and easy-to-implement energy-saving upgrades available. For around $5000-7500 all of these changes, except the GSHP, could be implemented in a typical 2200 square foot house. And perhaps just as importantly, ensuring that the design includes a good area of sloped unshaded south-facing roof provides the future occupant of the house the potential to add PV and/or solar hot water.