I have a steel roofed home that is powered from a solar system 100m away. The only earth is that on the incoming power cable. (220V 50Hz)

Should I earth/ground my roof and if so to an independent earth close to the house or to the one on the incoming cable?

There are no solar panels on this roof but an electrical field of up to 100V/m is detected close to the inside of the roof which is the main concern.

  • 1
    \$\begingroup\$ Why is that a concern? The average electric field on Earth will be about 100 V/m. \$\endgroup\$
    – Justme
    Commented May 24, 2023 at 10:36
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    \$\begingroup\$ "but an electrical field of up to 100V/m is detected close to the inside of the roof" How exactly did you measure that? \$\endgroup\$
    – Lundin
    Commented May 24, 2023 at 10:44
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    \$\begingroup\$ Have you considered the size of the electric field you can produce when walking across a carpet? \$\endgroup\$
    – Andy aka
    Commented May 24, 2023 at 11:37
  • \$\begingroup\$ I'm not knowledgeable enough to say if 100 V / m is of concern, but any piece of metal that is electrically isolated will pick up electrical noise and re-radiate it. This might be the source of your electric field. \$\endgroup\$
    – C. Dunn
    Commented May 24, 2023 at 14:09
  • \$\begingroup\$ @Justme & Lundin I measured the AC electrical field with a Trified TF2 meter. It was positioned a few mm from the steel roof. I also did not hold the meter during measurements as the body absorbs AC electrical fields distorting the measurements. After personally feeling ill when exposed to electrical fields for long periods I started researching. I came across a good few scientific papers showing concerning health issues when there was exposure to excessive electrical fields. Andy the AC electrical fields are very different from static generated on a carpet. \$\endgroup\$
    – Jeff
    Commented May 29, 2023 at 7:52

1 Answer 1


If you live in an area where you are at risk from lightning strikes, you should bond a conductor to your metal roof and to a copper rod driven into the ground.

The fact that you have a wire to your house that extends 100m away greatly increases the probability that a lightning strike in the area will bring current to your house.

The fact that there is a 100V/m electric field in the air near your roof is not a risk factor. What is a risk factor is the frequency of lightning in your area, and the paths that lightning might take, (such as the 100m wire).

  • \$\begingroup\$ Most houses around the world are probably connected to a power grid through a cable, of variable length...? And also to the older copper wire telephone lines. \$\endgroup\$
    – Lundin
    Commented May 24, 2023 at 14:36

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