In recent years, calls for a stalwart shift toward renewable non-conventional natural resources as sources of energy have increased. Potential players in the renewable non-conventional energy sector include solar, wind, algae, geothermal, nuclear, hydropower and ocean (tidal or wave) alternatives. While these non-conventional options show promise, they have their drawbacks.

For a number of these non-conventional energy sources, the weather, atmospheric conditions and the environment have to cooperate for harnessing their energy. Wind might be in short supply for wind turbines, or cloud cover might interfere with solar energy collection. Geothermal plants have been known to deplete their energy source, sometimes unpredictably. This inconsistency and low reliability can be costly, especially when the goal is to convert an energy source into electricity for power distribution.

When the supply is inconsistent and unreliable, large quantities of power might not be generated from non-conventional energy sources. That is problematic if a country wants to depend on the energy source to meet the demands of powering an entire nation. The inconsistency, unreliability and unpredictability of non-conventional energy sectors that are still in their infancy lead to debate on whether the sectors are feasibly sustainable for the long term.

Pollution is a major ecological issue when it comes to non-conventional energy sources. Wind turbine farms create noise pollution. Nuclear reactors create toxic wastes that are harmful to living things, thus making storage, transport and disposal a serious challenge. Geothermal plants have been associated with toxic emissions such as sulfur dioxide, silica and heavy metal deposits of mercury, arsenic and boron.

Harmful risks from certain non-conventional energy sources are a reality. Wind energy farms are notorious for harming species of birds, bats and insects with windmill blades. Certain solar energy farms create intense hot zones in the atmosphere from the amount of heat bouncing off their reflective surfaces. These hot zones have harmed, blinded and killed passing birds and insects. The construction of facilities to take advantage of ocean energy can destabilize marine ecosystems, adversely affecting both nesting grounds and hunting grounds, threatening the future of entire species.

As for nuclear energy, there is the risk of a reactor meltdown. Earthquakes, floods, sinkholes, tornadoes, hurricanes and all manner of natural disasters can damage a nuclear plant, creating leaks and environmental contamination. Nuclear cleanup is not easy, and given the half-life of nuclear elements used in nuclear plants, it can be extensive. That length of time for recovery from a nuclear plant disaster might not sit well with constituents and political groups. Even if no nuclear meltdown takes place, nuclear plants produce harmful waste materials that are difficult to dispose of, transport and store.

Starting a farm or plant that leverages solar, wind, algae, geothermal, nuclear, hydropower and ocean avenues requires hefty funding and investments. Acquiring the real estate to place the windmills, solar panels, algae farm, geothermal facility, nuclear plant, hydropower dam and ocean center requires sizable upfront capital outlays to fund, build, maintain and implement the endeavors properly with infrastructure and technologies that are up to code standards. The large-scale production, maintenance and harvesting of algae can translate into exorbitant expenditures.

Geothermal and ocean energy sources require specific locations close to a geothermal or ocean energy source. Sometimes that access is not without risks and hazards, which could affect distribution networks and infrastructure. These risks and hazards, not to mention the insurance costs to cover them, might be too pricey for the project to be commercially viable under present technological standards. Some form of technological breakthrough is needed to further geothermal and ocean energy sectors. If unfavorable economics exist, these non-conventional energy sources can turn out to be too costly and inefficient to be relied upon.

Non-conventional energy sources that are location-specific have limited accessibility. Land-locked states can't have ocean energy sources available. States that do not have deserts, estuaries, geothermal locales, or large tracts of available land free of development won’t be able to take advantage of solar, hydropower, geothermal or wind energy resources.

Initial setup costs are steep for unconventional energy sources. The land management afterward can be taxing as well. Political groups in a state or city might try to hinder the progress of the project, especially if they argue about environmental concerns, displacement of people from large tracts of land or any other competing interests.

Wind farms are only practical in areas with a lot of wind, and even if the area is known to be windy, there will be moments when no winds blow. In that situation, a viable backup solution to address where the energy will come from to power up the electric grid is needed. Consider hydropower dams during a drought. Dams might seem advantageous during a boon year of water flow. However, when there’s a drought or an environmental concern from the redirection of natural water flow – whether it be interference with the salmon runs in the Pacific Northwest or the creation of toxic chemical runoff in southern California's Salton Sea – questions are raised. Even if drought isn't a problem, hydropower dams are still met with controversy from conservation groups about biological diversity loss, nutrient flow interference and erosion concerns. Controversies arise about how efficient the non-conventional energy resource can be during times of hardship. The non-conventional energy sector is still an industry in its infancy. Consequently, there will often be arguments and debates revolving around feasibility, efficiency and scalability.