Solar heating is a very efficient method of using solar energy, with the ability to absorb 900-1000w/m2 of heat from sunlight, compared to only 200-300w/m2 of electricity that could be generated ...

The new requirement threatens to slow the approval process for renewable energy projects as they race to begin construction before the deadline for tax credits.

Federal agencies have recently issued a barrage of restrictions that could halt construction of solar and wind farms on public and private lands.

Industry groups said the directive could create new delays and bottlenecks for renewable energy projects across the country.