adjective
BAD : Our main energetic source is nuclear power.
GOOD : Our main energy source is nuclear power.
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energetic = active and able to work or play for a long time: 'Does anyone feel energetic enough to go for another swim?' 'My mother was a bustling energetic woman, always in a hurry, always busy.'
energy = the power obtained from oil, coal, the sun, etc: 'Oil is not only an expensive source of energy, it's running out.' 'There should be more research into solar energy.'