The advantages of mains voltage lighting are often plain to see, but some of the benefits of a low voltage lighting scheme are less well understood. Here are some of the main points to consider.

Mains Voltage

Mains voltage systems are well understood by electricians, as they are usually familiar with 240v wall and ceiling lights and exterior lanterns. They may be unfamiliar with and therefore shy of low voltage installations in the garden and will try to put you off. The main advantages of 240volt installations are,

1. No need to use transformers
2. Easier installation of wall spotlights where hiding transformers can be difficult.
3. You don’t need to pay such close attention to voltage drop in 240v cables as you do at 12v
4. There are some good energy efficient 240 volt compact fluorescent lamps available.

One of the main disadvantages is that nearly all the 240volt cables in the garden must be armoured and/or have some other suitable protection against accidental damage. Only the last 2 metres to the light can be a flexible cable. This results in more ugly junction boxes and less flexibility. Another big disadvantage is that 240v lamps blowing will often trip out a circuit breaker, whereas this rarely happens with 12v lamps as the current surge is absorbed by the transformer.

Low Voltage

Once you have accepted that you will need transformers there are many benefits with low voltage lighting.

1. Safety – 12 volts is inherently safe for children and pets
2. A bigger range of good quality, smaller fittings to choose from.
3. Easier installation of cables in borders and planting – flexible cables to spike spotlights can be several times longer than to 240v garden lights and you can move them around more easily.
4. A better range of lamps to choose from which are brighter, whiter, more efficient and longer lasting than their 240 volt cousins. Some 12 volt lights are twice as efficient as their 240volt equivalents.
5. If you have an accident with a low voltage cable it is usually easier to fix.
6. Low voltage transformers and power supplies absorb transients such as those caused when a lamp blows and are, to a degree, tolerant of earth currents arising from a bit of damp in light fittings. A little bit of dampness might not affect a 12volt circuit but it could render a 240volt circuit unusable.

It is possible to use both 240volts and 12volts together in the garden – the only difference is that instead of just a junction box there is a transformer there as well. 240v GU10 lamps are not as bright as the 12volt MR16 lamps but they have a warmer quality, which might suit some situations better than the crisp look of low voltage lighting. Conversely you might need the low voltage crispness to bring out the best in foliage.

Electricians sometimes say they don’t want to use 12v lights because they have had problems with transformers in the past, but this is usually related to interior installations where poorly sited transformers have overheated in insulated locations, to use of older types of transformers in enclosures which were not as fully weatherproof as modern types, or condensation getting into electronic transformers which were not potted for outside use. The wide range of both magnetic and electronic transformers suitable for use outside really undermines this argument.