Insolation is dependent on both the intensity of the incoming sunlight received by the Earth's surface, the how long it's received (the hours of daylight per day). The higher the intensity and/or the longer the duration of the sunlight, the higher the insolation. Larger amounts of insolation should result in higher Earth surface temperatures.

The intensity of the incoming sunlight will depend on the angle at which the sunlight strikes the ground. This is dependent on the solar altitude, which is dependent on one's latitude (when we are looking at the average conditions all year long).

The number of daylight hours per day affects the insolation because the longer the sun illuminates the ground, the hotter it will be afterwards.