UPLUX 720 vs 840 LED Grow Light: Which Fixture Fits Your Grow?

By UPLUX Editorial Team — Updated September 8, 2026

A 720 vs 840 LED grow light comparison is not simply a question of adding 120 watts. The UPLUX 720 Spider has a clearly documented efficiency, control and certification package. The UPLUX 840 Spider Pro is the higher-power option, with Top-Bin Samsung LEDs, passive cooling, daisy-chain capability and a 3-year warranty.

The practical answer is straightforward: choose the 720 when verified efficiency, broad input voltage and flexible dimming are central to the specification. Choose the 840 when the project deliberately calls for a higher-wattage fixture and values its thermal design, LED source, daisy-chain capability and warranty. More power is useful only when the canopy plan, electrical design and mounting conditions can use it.

What makes 720W and 840W lights different?

The nominal power difference is 120 W per fixture: 720 W versus 840 W. Across ten fixtures, that becomes 7.2 kW versus 8.4 kW of nominal lighting load—a 1.2 kW difference before any project-specific allowances. That matters to circuit planning, heat management and operating cost, but wattage alone does not prove canopy coverage or photon output.

The UPLUX 720 combines a six-bar design with a verified PPE of 3.0 µmol/J, a built-in driver, manual dimmer and 0–10V control. Its documented input range is 110–277 VAC, and its verified approvals include ETL, CE and UKCA. The UPLUX 840 is defined by its higher 840 W input, Top-Bin Samsung LEDs, passive thermal cooling, daisy-chain capability and 3-year warranty.

Which wattage fits your grow room size?

Room size is only the starting point. A responsible fixture plan also needs canopy dimensions, target intensity, mounting height, bench or aisle layout, available voltage and the required uniformity. A 720 vs 840 LED grow light decision should therefore follow a PPFD layout at the intended installation height—not a generic “4 × 4” or “5 × 5” label.

The 720’s six-bar architecture distributes its emitting area across the fixture, while its manual dimmer and 0–10V input give the operator two documented ways to manage output. The 840 adds nominal power and brings a different commercial package: Top-Bin Samsung LEDs, passive cooling, daisy-chain capability and a 3-year warranty. The correct choice depends on which package fits the planned grid and operating method.

Choose the UPLUX 720 if…

• You need a verified 3.0 µmol/J PPE value for the project comparison.
• The installation requires documented 110–277 VAC compatibility and a built-in driver.
• Manual dimming or 0–10V control is part of the operating plan.
• ETL, CE and UKCA documentation is important to the purchasing decision.
• A six-bar fixture is a better physical fit for the planned overhead layout.

Choose the UPLUX 840 if…

• Your lighting design intentionally specifies an 840 W fixture rather than assuming that more wattage is automatically better.
• Top-Bin Samsung LEDs are part of the required component specification.
• Passive thermal cooling is a priority for the installation.
• Daisy-chain capability supports the intended fixture arrangement.
• A documented 3-year warranty is important to the procurement decision.

For multi-fixture rooms, use the UPLUX grow room lighting design guide to work from canopy maps, spacing and mounting height before fixing the final quantity.

How do efficiency and spectrum compare?

The strongest verified efficiency statement in this comparison belongs to the UPLUX 720: 3.0 µmol/J PPE. UPLUX documentation currently contains conflicting PPF figures for the 840, so this article does not select one or use it to manufacture a comparison. The current figure should be confirmed with UPLUX before the 840 is specified for a project.

Why wattage alone cannot pick a spectrum winner

Wattage describes electrical input. It does not, by itself, describe the spectrum, photon output or distribution across a canopy. That is why the earlier “Which Spectrum Wins” framing was misleading: a useful comparison needs the current spectral file, a reliable output figure and a PPFD map at the proposed height.

If you need a refresher on PPF, PPFD, PPE and spectrum, the UPLUX LED grow light guide explains how the metrics work together. For procurement decisions, the commercial buyer’s guide shows how to compare them with controls, certifications and total operating cost.

What changes at commercial scale?

Electrical load and operating cost

The 840 draws 120 W more nominal power per fixture. That difference compounds in a large array, so the lighting choice should be reviewed with circuit capacity, daily photoperiod and HVAC load. The 720 provides a documented 110–277 VAC range; the current electrical specification for the 840 should be confirmed before circuit design.

Control, installation and service planning

The 720 includes a built-in driver, manual dimmer and 0–10V control. The 840 provides daisy-chain capability and passive cooling. These are different practical strengths: one gives the project clearly documented control and input options; the other supports linked installation planning and passive thermal management.

If centralized operation is required, review the UPLUX Controller and confirm compatibility for the exact fixture revision before ordering. Control cabling, fixture count and daily schedules should be defined alongside the lighting layout.

What should professional growers compare before ordering?

1. Canopy and room: usable canopy dimensions, aisles, obstructions and available mounting height.
2. Lighting target: the required PPFD range and uniformity across the real canopy—not only the center point.
3. Electrical design: total nominal load, supply voltage, circuit capacity and daily operating hours.
4. Control: manual dimming, 0–10V needs, controller compatibility and fixture-linking requirements.
5. Thermal plan: fixture heat, passive cooling strategy and the facility’s HVAC capacity.
6. Procurement: approvals, warranty, current technical documents and service requirements.

This checklist prevents a common buying error: selecting a fixture from wattage alone and trying to make the room fit it afterward. Start with the crop and facility, then select the fixture that makes the complete plan easier to operate.

Which light wins the 720 vs 840 debate?

The UPLUX 720 is the clearer choice when the decision depends on verified efficiency, flexible dimming, broad documented input voltage and named certifications. Its 3.0 µmol/J PPE, six-bar design, 0–10V control, manual dimmer, built-in driver and ETL/CE/UKCA package give a buyer concrete data to specify.

The UPLUX 840 is the stronger choice when the project intentionally needs the higher-wattage option and prioritizes Top-Bin Samsung LEDs, passive cooling, daisy-chain capability and a 3-year warranty. Confirm the current PPF and project-specific electrical details before the fixture count and spacing are finalized.

Not sure which fixture fits your project? Send UPLUX your canopy dimensions, mounting height, supply voltage and control requirements. The team can help match the product to the room instead of forcing the room around a headline wattage.