Fixtures
15
Total Watts
75W
Annual Cost
$24.64
詳細ガイド 近日公開
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Garden lighting calculation determines the number, type, and placement of outdoor light fixtures needed to create safe, beautiful, and functional nighttime garden spaces. The outdoor lighting market has grown to over $10 billion annually in the US, with LED technology making sophisticated garden lighting more affordable and energy-efficient than ever. Proper garden lighting serves three functions: safety (illuminating pathways, steps, and entry areas to prevent falls), security (deterring intruders through visible illumination), and aesthetics (highlighting garden features, trees, and architecture for dramatic nighttime effect). The calculation involves determining light levels needed for each area (measured in foot-candles), the illuminated area of each fixture type, and the spacing needed to achieve continuous coverage without dark gaps or glare. Pathway lighting typically needs 1–2 foot-candles for safe navigation; accent lighting for trees and walls aims for 2–5 foot-candles at the feature; security lighting needs 2–5 foot-candles in perimeter areas. Modern LED landscape fixtures consume 3–10 watts each — a complete system with 20–30 fixtures uses only 60–200 watts total, a fraction of the energy of older halogen systems.
Fixture Spacing = 2 × Beam Radius at ground level Beam Radius = Distance × tan(Beam Angle / 2) Number of Fixtures = Path Length / Fixture Spacing (for path lights)
- 1Step 1: Walk the garden at night and identify all areas needing illumination: paths, steps, trees, walls, entry.
- 2Step 2: Categorize each area by lighting purpose: safety, security, or accent.
- 3Step 3: Determine fixture type for each area: path lights (downward), spotlights (directional), flood lights (wide area), uplights (tree illumination).
- 4Step 4: Calculate path light spacing: typically 6–10 feet apart for overlapping illumination on paths.
- 5Step 5: For accent lighting, aim fixtures at 30–45 degree angles to minimize glare while highlighting texture and form.
- 6Step 6: Size the transformer for low-voltage systems: total system wattage × 1.25 safety factor = minimum transformer capacity.
50/8=6.25→7 lights. Place alternating left and right side of path for staggered light pattern that eliminates dark strips. Use 4–6W LED path lights at 8–10 inch height. System load: 7 × 5W = 35W.
Place 2 uplights per tree at 45-degree angles from opposite sides to illuminate both sides of canopy. Stake 2–4 ft from trunk, aim at 30–45 degree angle. 6 × 10W = 60W. Transformer: 60 × 1.25 = 75W minimum.
Total: (8×5)+(6×10)+(4×2)+(2×15)=40+60+8+30=138W. Transformer: 138×1.25=172.5W → select 200W transformer. For 12V low-voltage system, maximum wire run 100 ft from transformer.
Solar path lights work well in full-sun locations but fail in shaded gardens or during extended cloudy weather. Wired low-voltage LED systems provide consistent, reliable illumination regardless of weather but require installation effort. For shaded gardens or year-round reliability, wired systems are worth the investment.
Designing complete low-voltage landscape lighting systems for residential gardens
Calculating transformer sizing for outdoor lighting installations
Planning step and pathway lighting for safety in outdoor entertainment spaces
Dark Sky Compliant Lighting
The International Dark-Sky Association (IDA) certifies fixtures that minimize upward light emission and glare — important for astronomical observation areas and communities that want to preserve dark skies. Dark sky compliant fixtures direct all light downward and use warm color temperatures (2,700K or below). Many municipalities near observatories require dark-sky compliant outdoor lighting.
GFCI Requirements for Outdoor Lighting
All outdoor electrical outlets and outdoor landscape lighting connections must be GFCI (Ground Fault Circuit Interrupter) protected per NEC 210.8. Low-voltage transformer outlets should be GFCI. Line-voltage in-ground and well lights must be connected through GFCI-protected circuits. Buried low-voltage cable should be 6–8 inches deep to prevent accidental cutting during garden maintenance.
When input values approach zero or become negative, the Garden Lighting
When input values approach zero or become negative, the Garden Lighting Calculator calculation may produce undefined or misleading results. Always validate that inputs fall within the model's valid range before interpreting outputs. Extreme values should be flagged for manual review.
| Fixture Type | Application | Typical Wattage | Spacing/Coverage |
|---|---|---|---|
| Path light | Walkways, borders | 3–7W LED | 6–10 ft between lights |
| Spotlight/Directional | Trees, sculptures | 5–15W LED | 1–2 per feature |
| Flood light | Large walls, areas | 10–30W LED | 15–25 ft coverage |
| Step light | Stairs, risers | 1–3W LED | Every step or every other |
| Well light (in-ground) | Uplighting trees | 5–10W LED | 1–2 per tree |
| Wall sconce | Entryways, walls | 5–15W LED | Per entry/wall location |
| Underwater light | Pond/water feature | 3–10W LED | Per feature |
What is the difference between low-voltage and line-voltage landscape lighting?
Low-voltage systems (12V) are the standard for residential landscape lighting — they are safe to handle, DIY-friendly, use a transformer plugged into a standard outlet, and can be easily extended and modified. Line-voltage systems (120V) are used for high-power fixtures, in-ground lights that must be accessible by licensed electricians, and large commercial installations. 12V LED systems are safe, energy-efficient, and suitable for 95% of residential applications.
How do I size a low-voltage transformer?
Sum the wattage of all LED fixtures in the system. Multiply by 1.25 for a safety factor. Select a transformer at or above that wattage. A 150W transformer handles a typical 10–15 fixture system. Multi-zone transformers allow setting different zones on different timers (pathway lights on all night, accent lights only until midnight).
Can I mix LED and halogen fixtures on the same transformer?
Technically possible but not recommended — halogen fixtures draw much more wattage per lumen and age faster. If upgrading an older halogen system, replace all fixtures with LED for consistent performance and to significantly reduce transformer load. An old 300W halogen system can often be replaced with a 100W LED system providing equal or better light quality.
What color temperature should I use for garden lighting?
Warm white (2,700–3,000K) is the near-universal choice for residential landscape lighting — it provides a welcoming, golden glow similar to candlelight that flatters both plants and people. Neutral white (4,000K) is occasionally used for security lighting where color accuracy matters. Avoid cool white or daylight color temperatures (5,000–6,500K) for any aesthetic landscape application — they look cold and industrial.
How do I prevent light pollution and glare from garden lights?
Use fixtures with shields, shades, or baffles that direct light downward or at specific targets. Avoid pointing bright fixtures directly at neighboring properties or upward into the sky. Use the lowest effective light level — 2–3 foot-candles is adequate for most garden applications. Choose fixtures that meet Dark Sky Association standards for minimal light pollution contribution.
Should garden lights be on a timer or motion sensor?
Timers are ideal for aesthetic accent lighting and pathway lights — program them to run from dusk to 11 PM for entertaining hours and automatically shut off for energy savings. Motion sensors work well for security and driveway areas where continuous illumination isn't needed. Smart outdoor lighting controllers can combine both: aesthetic zones on a timer, security zones on motion sensors.
How do I light steps safely?
Step lights should be embedded in the riser of each step, pointing downward and forward to illuminate the tread without glare. Place every other step at minimum (ideally every step) for safety. Step lights consume only 1–3 watts each and are critical safety features — falls on unlit outdoor steps are a leading cause of nighttime landscape accidents. Use fully sealed, wet-rated fixtures designed for in-step installation.
プロのヒント
Before installing any fixtures permanently, use temporary landscape lighting (battery-powered LED fixtures or even a flashlight) to test your lighting design at night. Walk the garden, look from inside the house, and adjust positions until you are happy with the effect. This 'test in the dark' step prevents costly relocations after permanent installation.
ご存知でしたか？
The first decorative outdoor electric lighting was installed at the 1893 World's Columbian Exposition in Chicago — the 'White City' used 100,000 incandescent bulbs to illuminate the fairgrounds at night, creating a spectacle that drew millions of visitors who had never seen electric outdoor lighting. It was so impressive that it is credited with popularizing electricity as the future of lighting and accelerating the global transition away from gas lighting.