A rough guide to voltage drop using 12 volt lighting. Follow all safety instructions for your transformer!
| Shelby Landscaping Lighting Guide (Voltage drop should not exceed 1.5V) | voltage drop using 8-2 wire 100 ft. | if most watts are in second half of run | voltage drop using 10-2 wire 100 ft. | if most watts are in second half of run | voltage drop using 12-2 wire 100 ft. | if most watts are in second half of run | |
| run w/ 2 35 watt lamps (70 watts) | 70 | 0.37 | 0.43 | 0.59 | 0.68 | 0.93 | 1.08 |
| run w/ 3 35 watt lamps (105 watts) | 105 | 0.55 | 0.64 | 0.88 | 1.02 | 1.40 | 1.62 |
| run w/ 4 35 watt lamps (140 watts) | 140 | 0.74 | 0.86 | 1.17 | 1.36 | 1.87 | 2.17 |
| run w/ 5 35 watt lamps (175 watts) | 175 | 0.92 | 1.07 | 1.47 | 1.70 | 2.33 | 2.71 |
| run w/ 6 35 watt lamps (210 watts) | 210 | 1.11 | 1.28 | 1.76 | 2.04 | 2.80 | 3.25 |
| 75ft runs (Voltage drop must not exceed 1.5V) | voltage drop using 8-2 wire 75 ft. | if most watts are in second half of run | voltage drop using 10-2 wire 75 ft. | if most watts are in second half of run | voltage drop using 12-2 wire 75 ft. | if most watts are in second half of run | |
| run w/ 3 35 watt lamps (105 watts) | 105 | 0.42 | 0.48 | 0.66 | 0.77 | 1.05 | 1.22 |
| run w/ 4 35 watt lamps (140 watts) | 140 | 0.55 | 0.64 | 0.88 | 1.02 | 1.40 | 1.62 |
| run w/ 5 35 watt lamps (175 watts) | 175 | 0.69 | 0.80 | 1.10 | 1.28 | 1.75 | 2.03 |
| run w/ 6 35 watt lamps (210 watts) | 210 | 0.83 | 0.96 | 1.32 | 1.53 | 2.10 | 2.44 |
| run w/ 7 35 watt lamps (245 watts) | 245 | 0.97 | 1.12 | 1.54 | 1.79 | 2.45 | 2.84 |
| run w/ 8 35 watt lamps (280 watts) | 280 | 1.11 | 1.28 | 1.76 | 2.04 | 2.80 | 3.25 |
| 50ft runs (Voltage drop must not exceed 1.5V) | voltage drop using 8-2 wire 50 ft. | if most watts are in second half of run | voltage drop using 10-2 wire 50 ft. | if most watts are in second half of run | voltage drop using 12-2 wire 50 ft. | if most watts are in second half of run | |
| run w/ 3 35 watt lamps (105 watts) | 105 | 0.28 | 0.32 | 0.44 | 0.51 | 0.70 | 0.81 |
| run w/ 4 35 watt lamps (140 watts) | 140 | 0.37 | 0.43 | 0.59 | 0.68 | 0.93 | 1.08 |
| run w/ 5 35 watt lamps (175 watts) | 175 | 0.46 | 0.54 | 0.73 | 0.85 | 1.17 | 1.35 |
| run w/ 6 35 watt lamps (210 watts) | 210 | 0.55 | 0.64 | 0.88 | 1.02 | 1.40 | 1.62 |
| run w/ 7 35 watt lamps (245 watts) | 245 | 0.65 | 0.75 | 1.03 | 1.19 | 1.63 | 1.89 |
| run w/ 8 35 watt lamps (280 watts) | 280 | 0.74 | 0.86 | 1.17 | 1.36 | 1.87 | 2.17 |
| A lamp seeing a voltage drop from 12V to 10V will have 50% candlepower output | |||||||