Planets in houses · Kendra
Surya in the 1st house
Sun · Tanu Bhava
Surya is the karaka (significator) of soul, father, authority and vitality. The 1st house, called Tanu Bhava, shows self, body and personality. When Surya sits here, these matters take on its colour.
A malefic in the Lagna gives strength of will and drive, but can make one impatient or harsh and needs care for health.
The 1st house is a kendra (angular house), a pillar of the chart, so a graha here shows its results openly and strongly.
Surya gives its best results here when it is exalted in Mesha, in its own sign (Simha) or in a friendly sign, and when it is not combust.
Results are weaker if the Sun is debilitated in Tula or afflicted by Saturn or Rahu.
In transit (gochar)
When Surya transits the 1st house counted from your Moon sign, the period traditionally needs more care.
A single placement is never read alone: sign, aspects, conjunctions, dasha and the whole chart change the outcome.