Kolibrianswered grow question 5y ago Yes, the output of two lamps adds up.
This way, you can expect significantly more PAR in the areas where the light cones overlap.
It's also possible to use the XS 1500, for example, for the vegetation stage and turn on the second lamp during flowering, or simply to light a larger area.
However, another, stronger lamp is still a good option and should be purchased if the budget allows.
Good luck!