Landscape Lighting Transformer Calculator
Estimate a preliminary low-voltage landscape-lighting transformer size, load utilization, annual energy use and transformer planning cost.
Default project preview
150 W
Fixture connected load
108 W
Total connected load
108 W
Loss-adjusted load
118.8 W
Selected-load utilization
79.2%
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Light fixtures
Enter this project assumption in a unitless value. The current imperial default is 18. Minimum: 1.
Watts per fixture
Enter this project assumption in W. The current imperial default is 6 W.
Additional connected load
Enter this project assumption in W. The current imperial default is 0 W. Minimum: 0.
Cable and driver loss allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Future spare capacity
Enter this project assumption in %. The current imperial default is 25 %. Minimum: 0. Maximum: 100.
Transformer price allowance
Enter this project assumption in per W. The current imperial default is 0.8 per W. Minimum: 0.
Operating hours per night
Enter this project assumption in h. The current imperial default is 5 h. Minimum: 0. Maximum: 24.
Electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
Fixture connected load
18 fixtures × 6 W. Default preview: 108 W.
Total connected load
fixtures plus additional load. Default preview: 108 W.
Loss-adjusted load
10% allowance. Default preview: 118.8 W.
Selected-load utilization
loss-adjusted load ÷ selected size. Default preview: 79.2%.
Annual fixture energy
5 hours per night. Default preview: 197.1 kWh.
Transformer and annual energy
entered planning rates. Default preview: $120.00 + $35.48/yr.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Connected load = fixture count × watts per fixture + other load. Loss and spare-capacity allowances are applied, then the result is rounded up to a common transformer size.
FAQ
Landscape Lighting Transformer Calculator questions
Why include cable and driver losses?+
The transformer supplies more than the fixture nameplate load because wiring and electronic components consume some power.
Why add spare capacity?+
A reserve allows modest future fixture additions and keeps the transformer from being planned at its exact calculated demand.
Does transformer wattage solve voltage drop?+
No. Voltage drop also depends on cable gauge, current, run length, branching and transformer taps.