Both are myths.
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In its most extreme form, the energy myth claims that renewable energy requires more energy invested than it generates over its lifetime. A less extreme version is that renewable electricity has low net energy or low Energy Return on Energy Invested (EROEI) and so will compete excessively with the energy needs of other sectors of the economy.
These are cunning myths because they were true several decades ago when solar photovoltaic (PV) systems were made individually to power the early artificial satellites. But nowadays, PV modules are mass produced and have much lower energy inputs, much higher energy conversion efficiencies and longer lifetimes.
The fall in energy inputs is reflected in their rapid cost reductions. They generate the life-cycle energy required to construct themselves in one to two years, depending on their type and location, and their lifetime is at least 25 years.
A large wind turbine with a similar lifetime generates the life-cycle energy required to construct itself in six to 12 months.
A separate but related net energy issue arises if the transition to a large-scale renewable electricity system occurs so rapidly that one batch of solar and wind farms is installed before the previous batch has generated the energy needed to build itself.
Then temporarily, while the rapid transition is occurring, more energy is invested in the whole electricity system than the energy it generates.
However, after the transition is complete or slows down, energy generation will overtake and surpass energy investment.
This situation would be worse if nuclear power, with its very long construction time, were used instead of renewables to substitute for fossil fuelled electricity.
The responsibility for the situation belongs to industries and governments that have delayed the transition for so long that now a very rapid transition is needed to try to avoid climate tipping points.
Next, the CO2 myth.
Although most of the energy inputs to manufacturing wind turbines and solar panels are derived from fossil fuels in most of the world, this is changing rapidly.
Electricity use in both mining and minerals processing is shifting to renewables because it's cheaper than fossil electricity.
Soon even the diesel-powered mining vehicles will be replaced with battery-electric vehicles powered by renewables.
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