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Third-rail systems can suffer disruption in cold weather due to ice forming on the conductor rail. For passenger operation it is possible to provide enough power with diesel engines (see e.g. 'ICE TD') but, at higher speeds, this proves costly and impractical. Adaptors were available from 15 A down to 5 A and from 5 A down to 2 A so in practice it was possible for an appliance with the smallest size of flex to be protected only by a 15 A fuse. Shaver adaptors must have a 1 A BS 646 fuse. When converting lines to electric, the connections with other lines must be considered. If through traffic is to have any benefit, time-consuming engine switches must occur to make such connections or expensive dual mode engines must be used. Theft: the high scrap value of copper and the unguarded, remote installations make overhead cables an attractive target for scrap metal thieves. The overhead wires make the service "visible" even in no bus is running and the existence of the infrastructure gives some long-term expectations of the line being in operation. There are a number of advantages including the fact there is no exposure of passengers to exhaust from the locomotive and lower cost of building, running and maintaining locomotives and multiple units.

The same applies to the kind of push-pull trains which have a locomotive at each end. Those who fail to adhere to well known best practices for safety have been held negligent. Ground is a safety conductor with a low impedance path to earth. Appearance: the overhead line structures and cabling can have a significant landscape impact compared with a non-electrified or third rail electrified line that has only occasional signalling equipment above ground level. However, due to ventilation issues, diesel trains may have to be banned from certain tunnels and underground train stations mitigating the advantage of diesel trains somewhat. In theory, these trains could enjoy dramatic savings through electrification, but it can be too costly to extend electrification to isolated areas, and unless an entire network is electrified, companies often find that they need to continue use of diesel trains even if sections are electrified. It also means that, if trains are stopped and have to be evacuated, the current has to be turned off before passengers can be allowed to wander the track. British standards have proliferated throughout large parts of the former British Empire. Birds may perch on parts with different charges, and animals may also touch the electrification system.

For two decades, industry officials and the North American Electric Reliability Council (NERC) have warned that restructuring the electricity system would destroy it. Polarized 1-15P plugs will fit 5-15R grounded receptacles, which have the same wider slot for the neutral blade. BS 1363 type plugs (to a recognized standard) to BS 1363 sockets. By the 1927 revision of BS 73 four sizes of two-pin plugs and sockets were standardized: 2 A, 5 A, 15 A and 30 A. This was later superseded by BS 372:1930 part 1 Two-pin Side-entry Wall Plugs And Sockets for Domestic Purposes. Historically, two-pin sockets without earth were used in Britain, but their use is now restricted to sockets specifically designated for shavers and toothbrushes. In 2014, progress is being made in the use of large capacitors to power electric vehicles between stations, and so avoid the need for overhead wires between those stations. Large fossil fuel power stations operate at high efficiency, and can be used for district heating or to produce district cooling, leading to a higher total efficiency. On the other hand, electrification may not be suitable for lines with low frequency of traffic, because lower running cost of trains may be outweighed by the high cost of the electrification infrastructure.

This is mostly an issue for long-distance trips, but many lines come to be dominated by through traffic from long-haul freight trains (usually running coal, ore, or containers to or from ports). There are some additional maintenance costs associated with the electrical equipment around the track, such as power sub-stations and the catenary wire itself, but, if there is sufficient traffic, the reduced track and especially the lower engine maintenance and running costs exceed the costs of this maintenance significantly. Network effects are a large factor with electrification. The strand is placed under tension to prevent excessive sag; typical strand tension is a few hundred pounds, although a strand supporting a large multipair cable may be tensioned as high as 1000 pounds. Britain intercepted these signals, diagnosed how the encrypting machine worked, and decrypted a large amount of teleprinter traffic. Another aspect that can raise the cost of electrification are the alterations or upgrades to railway signalling needed for new traffic characteristics, and to protect signalling circuitry and track circuits from interference by traction current. Direct Current offers an alternative to the conventional AC transmission that cures many of AC's defects. These companies developed AC systems, but the technical difference between direct and alternating current systems required a much longer technical merger.

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