If you're referring to the sun:
* Lunar: Relating to the moon.
* Terrestrial: Relating to the Earth.
* Non-solar: This is a literal opposite, but might not be as common in everyday language.
If you're referring to energy sources:
* Fossil fuel: Derived from the remains of ancient organisms.
* Nuclear: Derived from nuclear fission or fusion.
* Wind: Energy generated from wind.
* Hydro: Energy generated from water.
* Geothermal: Energy derived from the Earth's internal heat.
If you're referring to something that uses solar power:
* Non-solar: This would apply to any device or technology that doesn't use solar power.
Ultimately, the best antonym for "solar" depends on the specific situation and what you're trying to convey.
