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âš¡ Tru-Scapes Sizing Guide
What Size Transformer Do I Need?
Choosing the correct transformer is one of the most important steps when designing and installing a low voltage outdoor LED lighting system. A properly sized transformer ensures your lights perform correctly, maintain consistent brightness, and operate safely for years to come.
100W
Small Systems
200W
Medium Systems
400W
Large & Multi-Zone
Step-By-Step
How to Calculate the Right Size
Sizing your transformer takes just two simple steps — add up your fixture wattage, then apply our recommended capacity rule.
1
Calculate Total Wattage
Start by adding together the wattage of every fixture connected to the transformer.
10 LED path lights @ 4W each
40W
4 uplights @ 7W each
28W
2 hardscape lights @ 3W each
6W
Total Load
74 Watts
2
Add Capacity Headroom
For best performance and long-term reliability, we recommend loading transformers to approximately 70–80% of maximum capacity. This allows room for:
- ✓ Voltage fluctuations
- ✓ Future fixture additions
- ✓ Longer wire runs
- ✓ Cooler transformer operation
- ✓ Improved LED performance and lifespan
Sizing Chart
Recommended Transformer Sizing
Match your total fixture wattage to the right transformer size. All Tru-Scapes transformers operate on low voltage AC power and are designed for professional-grade outdoor LED lighting systems.
| Total Fixture Wattage | Recommended Transformer |
|---|---|
| 1 – 70 Watts | 100 Watt Transformer |
| 71 – 160 Watts | 200 Watt Transformer |
| 161 – 320 Watts | 400 Watt Transformer |
Wire & Zones
Wiring & Zone Recommendations
Pair your transformer with the right wire gauge and take advantage of multiple zones for larger projects.
Recommended Wire Size
Tru-Scapes recommends a minimum of 12/2 low voltage direct burial wire for outdoor LED lighting installations. Using larger gauge wire helps reduce voltage drop, improves system performance, and allows for longer wire runs.
- ✓ 12/2 wire recommended for most residential installations
- ✓ Larger systems or longer runs may require heavier gauge wire
- ✓ Avoid undersized wire to prevent dimming and voltage loss
Understanding Transformer Zones
Our 400 watt transformer includes 2 separate zones. This allows contractors and homeowners to:
- ✓ Separate front and backyard lighting
- ✓ Divide larger systems into multiple wire runs
- ✓ Reduce voltage drop
- ✓ Simplify troubleshooting and maintenance
Benefits
Why Proper Sizing Matters
Choosing the right transformer size protects your investment and ensures your lighting system performs at its best for years to come.
Consistent Brightness
Longer Fixture Lifespan
Voltage Regulation
Future Expansion
Long-Term Performance
At a Glance
Quick Reference Chart
Find the right transformer at a glance — matched to system size and typical applications.
| Transformer Size | Ideal LED Load | Best Applications |
|---|---|---|
| 100 Watt | Up to ~70 Watts | Small landscape lighting systems |
| 200 Watt | Up to ~160 Watts | Medium-sized homes & outdoor living areas |
| 400 Watt (2 Zone) | Up to ~320 Watts | Large properties & multi-zone systems |
FAQs
Frequently Asked Questions
Everything you need to know about choosing and sizing your low voltage outdoor LED lighting transformer.
Start by adding up the total wattage of every fixture in your lighting system. Then choose a transformer that allows your total load to fall within 70–80% of the transformer's maximum capacity. For example, if your total fixture wattage is 74 watts, a 100 watt transformer would be the right choice. This headroom ensures consistent brightness, reduces heat, and allows room for future expansion.
Loading a transformer to full capacity puts unnecessary stress on the unit and can shorten its lifespan. By keeping the load at 70–80%, you allow room for voltage fluctuations, longer wire runs, and future fixture additions. It also keeps the transformer running cooler, which improves overall LED performance and reliability over time.
Tru-Scapes recommends a minimum of 12/2 low voltage direct burial wire for most outdoor LED lighting installations. Larger systems or longer wire runs may require a heavier gauge to reduce voltage drop. Using undersized wire can cause dimming, voltage loss, and inconsistent performance — so it's always better to err on the side of a larger gauge.
Zones are independent output channels on a transformer that let you run separate wire lines from the same unit. Our 400 watt transformer includes 2 separate zones, which is ideal for splitting front and backyard lighting, dividing large systems into shorter runs, reducing voltage drop, and simplifying troubleshooting and maintenance. Multi-zone transformers are especially useful for larger properties.
Yes — and that's exactly why we recommend the 70–80% loading rule. By not maxing out your transformer at the time of install, you leave room to add path lights, uplights, or hardscape fixtures down the road without needing to upgrade your transformer. Planning ahead at install saves time and money later.
An undersized transformer will struggle to power all of your fixtures properly. You may notice dim or flickering lights, inconsistent brightness across the system, voltage drop on longer runs, and a shorter lifespan for both the transformer and your LED fixtures. Always size up to the next transformer category if your total load is close to the maximum capacity of a smaller unit.
Yes. All Tru-Scapes transformers are designed specifically for outdoor low voltage LED lighting systems. They operate on safe low voltage AC power and are built to professional-grade standards for long-term reliability in outdoor environments. For installation help, fixture layout, or voltage drop planning, we always recommend working with a local Tru-Scapes authorized dealer.
Need Help Designing Your Lighting System?
Contact a local Tru-Scapes authorized dealer for assistance selecting the proper transformer, wire size, fixture layout, and voltage drop planning for your outdoor lighting project.
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