Almost all low voltage garden lighting systems consist of three basic elements: a mains powered low voltage (typically 12 volts) transformer; a cable that runs through the areas requiring lights; and the light fittings themselves.

The most important things to decide on initially are the type of lighting (LED or conventional incandescent) and the size of the transformer, since this determines the amount of lighting (a combination of the number of fittings and their brightness) that can be run.

We will touch on how the two types of lighting differ and how to mix them together later, but for now just understand that in principle they both function pretty much the same way.

To gauge the correct size of transformer, count up the total number of watts for all your various light fittings (i.e. if you have 2 x 20w spots and 3 x 10w rock lights thats a total of 70 watts) and ensure you purchase a transformer that is rated to handle that load.

As with any mains powered device, the transformer must be situated indoors and the cable connected to it and then routed into the garden.

Note that the cable itself adds some load additional to the load caused by the light fixtures. You should make an adjustment for this when sizing your transformer – the cable packaging usually states its load, and obviously the longer the cable the greater the load, which limits how long your cable can be and remain effective.

It’s simple to determine whether a cable is too long since the lights are a) not as bright as they should be and b) discernibly dimmer the further away from the transformer they are. An effective remedy involves looping the cable (or running additional cable) back to nearer the transformer. It is imperative though that you do not cross-connect the two strands of wire that make up the cable – there is typically some type of marking on one of the strands so you can easily observe polarity.

After you have connected the cable and laid it out then you can attach each low voltage light fixture by simply cutting and re-joining the cable incorporating the cable attached to the fixture.

As already noted above, LED and regular incandescent garden light system are now both readily available, which can tend to confuse things when deciding which to purchase or how best to incorporate both types.

LED lights use considerably less power and do not generate any heat. They also produce much crisper, sharper light compared to incandescent lamps, which can be used to good effect or can look rather harsh depending on the effects you’re after.

In general you cannot attach LED light fittings to a normal low voltage garden system, and the reverse also applies. In the first case, the LED light will likely fail within weeks and in the second, the LED transformer (commonly called an LED driver) will quickly self-destruct.

There are a few exceptions -some types of LED light are suitable for use on a conventional low voltage system, but these will state this on their packaging. Otherwise, to mix LED and incandescent low voltage garden lights you will need to lay out two separate cables – one connected to a regular 12v transformer and one to a constant voltage LED driver – and match the correct sorts of light fitting to the appropriate cable.

There are significant advantages to running both kinds of garden lighting. LED light has a distinct quality that makes possible a whole new range of lighting effects and, when combined, both kinds of lighting system can be deployed so as to enhance or contrast each other, creating lighting effects beyond the capabilities of either one alone.