It's important that you use professional-grade transformers with professional-grade lights? Why? For starters, transformers of lesser quality simply don't regulate power very well. The result is they shorten the lives of your deck lights and can even be a hazard.
Secondly, cheaper transformers are loud! They hum, providing more noise than comfort and taking away from the experience to be had from enjoying a well-illuminated deck at night.
These quiet, professional-grade transformers are a necessity for operating a low-voltage lighting system. They mount to your home’s exterior and plug directly into the GFI outdoor receptacle (usually already existing). They range in wattage from 100-1200 watts; your application determines the size you need. (For instance, if you were to buy six step lights at 7w each and 12 railing lights at 11w each, you’d need a transformer capable of handling at least 174 watts – it is usually recommend that you have a minimum of 50-100 ‘free’ watts as well).
Made in China.