Bridlewood Electromagnetic Fields (EMFs) Information Service
Bridlewood Electromagnetic Fields (EMFs) Information Service

Typical EMF Levels for Transmission Lines

Type of Line Right of Way 15m/50ft 30m/100ft 61m/200ft 91m/300ft
115 kV 1.0 kV/m

29.7 mG

0.5 kV/m

6.5 mG

0.07 kV/m

1.7 mG

0.01 kV/m

0.4 mG

0.003 kV/m

0.2 mG

230 kV 2.0 kV/m

57.5 mG

1.5 kV/m

19.5 mG

0.3 kV/m

7.1 mG

0.05 kV/m

1.8 mG

0.01 kV/m

0.8 mG

500 kV 7.0 kV/m

86.7 mG

3.0 kV/m


29.4 mG

1.0 kV/m

12.6 mG

0.3 kV/m

3.2 mG

0.1 kV/m


Distances are from edge of Right-of-Way
Electric Fields are measured in Kilovolt/Metres (kV/m)
Magnetic Fields are measured in milliGauss (mG)

These are typical EMFs at 1m/3.3ft above ground for various distances from power lines in the Pacific Northwest. They are for general information. For information about a specific line, contact the utility that operates the line. Source: Bonneville Power Administration 1994.

Electric fields from power lines are relatively stable because line voltage doesn't change very much. Magnetic fields on most lines fluctuate greatly as current changes in response to changing loads. Magnetic fields must be described statistically in terms of averages, maximums, etc., The magnetic fields above are means calculated for 321 power lines for 1990 annual mean loads. During peak loads (about 1% of the time), magnetic fields are about twice as strong as the mean levels above.

Above chart and text taken from Questions and Answers About EMF: Electric and Magnetic Fields Associated with the Use of Electric Power, January 1995. National Institute of Environmental Health Sciences and U.S. Department of Energy.