In the UK, when you are buying or selling a property, you may either commission yourself, or receive as part of your survey, a report from one of the automated services that uses online data to identify features of interest close to the property.
Firms offering such services include (we neither endorse nor recommend against any of these, we just note their existence):
These searches and reports will often report the presence of electricity equipment - overhead lines or substations. That may cause some concern to you, or may cause your surveyor to consider whether to adjust the value of the property.
However, these searches often report a substation or an overhead line that is at a distance far too far for EMFs even to be detectable, let alone a cause for serious concern. EMFs fall rapidly with distance from the source. It's impossible to be precise because every line or substation is different, and the definition of when we consider that the field has fallen to "background" or "negligible" levels is not straightforward. But we could say that the field is unlikely to be significant once it has fallen to the levels found in ordinary homes that aren't near any particular sources: anything from 0.01 - 0.2 µT in the UK - let's say 0.1 μT as a single guide figure.
On that basis:
| Field nearly always falls to levels in ordinary homes within 150 m (perhaps 90-110 m for a typical line, but it depends a lot on the line) | |
| Field nearly always falls to levels in ordinary homes within 100 m (perhaps 30-60 m for a typical line, but it depends a lot on the line) | |
| Field typically falls to levels in oridnary homes from a few metres to a few tens of metres depending on the line | |
| Field normally falls to levels in ordinary homes within a few metres of the perimeter fence | |
| Field normally falls to levels in ordinary homes within the first metre or two from the perimeter |
(in each case, we are talking primarily about the magnetic field - the electric field has even more limited effect inside homes.)
Other distances you may hear mentioned: epidemiological studies have come up with the field level 0.4 μT as a level where any risk for childhood leukaemia may appear. That's higher than the average field in UK homes, so not surprisingly, the distance for the field to fall to that level is smaller - 60 m on average for 400/275 kV lines, perhaps 30 m for 132 kV lines. On the other hand, 200 or 600 m are distances that came out of one specific study, the "CCRG" study, but that is probably less of a concern because of later results from that study where the finding seems to have gone away.
See more pictures to help you identify what a particular bit of the electricity system is.
The reason people flag up the presence of a power line or substation at all is because of scientific evidence about the possibility of a link to childhood leukaemia. But even if the overhead line or substation is close enough for it to produce an elevated field, that should not necessarily constitute a problem. The field will still be compliant with the exposures limits that are in place to protect the public. Each person will wish to make up their own mind, but there seems little reason from an EMF perspective why such homes should not be bought and sold like any other. But if the home is beyond the distances suggested above, the fields should be negligible and EMFs should probably not need to be a factor at all.
For a summary of the issues relating to the science, see: