Difference between Heliotherapy and Insolation

What is the difference between Heliotherapy and Insolation?

Heliotherapy as a noun is any medical therapy by exposure to light. while Insolation as a noun is the incident radiant energy emitted by the sun which reaches a unit horizontal area of the earth's surface; the rate of delivery of such radiation

We hope you now know whether to use Heliotherapy or Insolation in your sentence.