The longer the cord is the more resistance there is; ie the more electrical load on the circuit. As long as you are pulling less than what the circuit and cord is rated for, there isn’t an issue, you will just be wasting a little extra power from the extra resistance. The plugs can also have a bit of extra resistance.

Two pieces of advice that will make the biggest difference:

• Keep the total length of all extension cables used as short as is reasonable. Don’t use a 20m cable when a 4m cable will do.

• Buy extension cords with higher wire gauges (higher wire thicknesses). A 12 gauge cable (4mm^2^) will provide notably less resistance than a 14 (2.5mm^2^) or 16 gauge cable (1.5mm^2^). The packaging will say what gauge it is. Note, I’m talking about the thickness of the metal itself, not the thickness of the extension cord. I have seen some very, very thick extension cords with absolute trash wires inside.