Electricity systems and sources

Household wiring and appliances

In modern society we are all exposed to EMFs daily, because they are produced by anything which uses or transmits electricity. Much of our exposure comes from the appliances and wiring in our homes as described below.


Mains operated appliances are a source of EMFs. The magnitude of the EMFs produced depends on the appliance’s design, but also how much power it uses. Maximum magnetic fields from appliances can be over 70 µT at the surface of a microwave (these are the 50 Hz magnetic fields rather than the microwaves ‘escaping’ the appliance), and over 30 µT for a device like a washing machine. The fields reduce very rapidly with distance. For many appliances a background level of EMFs will be reached within 30 cm from the appliance. Most people do not spend significant time close to appliances so their overall EMF exposure from appliances is limited, but all appliances add to the background EMF level in the home.

Other common appliances to produce electric fields include kettles (maximum over 15 µT), TVs (maximum over 0.5 µT) and electric ovens (maximum over 5 µT).

Household wiring

Household wiring is usually designed to prevent magnetic fields as the current and return current should cancel each other, however this is not always the case.
There can be a connection in the house between neutral and earth, so that the currents are no longer balanced - this is called a net current - and a magnetic field is produced. Some older techniques of wiring including ring mains, and separate wires for the current and return current, can also be sources of magnetic field.  
Background fields typically vary between homes from below 0.01 µT to 0.2 µT. In any given home they also vary with time, broadly following daily and annual cycles based on electricity use.

Cancellation is not so effective for electric fields, and house wiring is often the main source of electric fields in the home.