Electricity transmission over long distances involves some loss of energy, primarily due to two factors: resistance and the inductance of the transmission lines.

Resistance: 

Electrical current flowing through conductors (like copper or aluminium wires) faces resistance, which causes some of the electrical energy to be lost as heat. 

The amount of energy lost due to resistance depends on the material of the conductor, its cross-sectional area, and the length of the transmission line. Generally, higher voltages are used for long-distance transmission to reduce these losses, as higher voltage means lower current for the same power, and lower current results in less resistive loss.

Inductance and Capacitance Effects: 

Long transmission lines also have inductance and capacitance, which can cause additional losses, mainly reactive power losses. These are more complex and depend on the alternating current (AC) nature of the power system and the specific characteristics of the transmission line.

The total transmission loss can vary significantly based on the distance, the condition of the transmission lines, the voltage level, and the load. On average, transmission losses in the electrical grid can be around 5-10%. For very long distances (hundreds of kilometres), the losses can be higher, especially if the transmission technology is not optimised for long distances (like using High Voltage Direct Current, HVDC, systems).

In advanced power systems, HVDC is often used for very long-distance or undersea transmissions, as it reduces these losses considerably compared to traditional alternating current (AC) transmission. HVDC transmission losses are typically lower, around 3% per 1000 kilometres, plus additional losses at the converter stations.