Dear Ray
Can one transformer run two areas of my house?
Dear Ray, I want path lights by the front walk and a few lights in the back patio bed. Can one transformer run both areas, or do I need two separate systems?
— Trying not to buy more equipment than I need
Dear Trying,
One transformer can often serve two areas of a house. The important question is not whether the beds are on different sides of the house; it is whether the total load and cable routes make sense together.
Begin by adding the wattage of every fixture you plan to run, then leave useful breathing room rather than filling the transformer to its label. Our transformer sizing guide can help you make that first pass. Two branches from the same transformer are normal, and they can be easier to service than a single cable wandering all the way around the house.
The catch is distance. A short front-walk branch and a much longer backyard branch do not experience power the same way. Put the longest or highest-load branch on a higher-voltage tap if your transformer provides one, and check the far fixtures after dark. If they look weaker than the first lights, that is a design clue, not an invitation to squint and hope.
I would use two transformers only when the total fixture load is beyond one unit's comfortable capacity, the cable route becomes unreasonable, or you genuinely want separate control. Plan the branches on paper first, and use the transformer planner to see the totals before you buy. One well-planned transformer is tidy. One overworked transformer is just an expensive night-light.
— Ray
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