Difference between High Pressure Sodium and Metal Halide Bulbs

July 16, 2015 by Editorial Team

If you are contemplating doing a little gardening or need outdoor lighting, you may want to know the difference between high pressure sodium and metal halide bulbs as it may come in handy. In recent years, people have gradually taken on the idea of growing a few vegetables in a greenhouse to offset the rising cost of groceries. High pressure sodium and metal halide bulbs are essential in indoor gardening and outdoor lighting. They produce high intensity discharge light that boost production. In order to make the right choice between these bulbs, the following is discussion of the differences between them.

Definitions

High pressure sodium bulb
High pressure sodium bulb

High pressure sodium bulbs are efficient electrical light sources that produce a wide spectrum of bright yellow light that is good for street lights and greenhouse use.

Metal halide bulb
Metal halide bulb

Metal halide bulbs are a type of high-intensity discharge gas (HID) electric lamps that are capable of producing light by use of an electric arc that has a mixture of gases (metal halides such as bromine or iodine and mercury). They produce intense white light that is suitable for use in greenhouses, high ceilinged places and outdoor locations such as streets and stadiums.

Comparison Chart

High pressure sodium bulbsMetal halide bulbs
Promotes flowering and fruiting in indoor gardeningPromotes vegetative growth in indoor gardening
Produces a reddish-yellow lightProduces white light
Produces about 96-150 lumens of light per wattProduces about 65-110 lumens of light per watt
Lifespan is about 2 to 6.5 thousand hoursLifespan is about 3 to 6.5 thousand hours

Comparison

The difference involves the type of spectrum of light they produce, their use in indoor gardening, their lifespan, and the number of lumens they produce per watt.

High pressure sodium bulbs and metal halide bulbs emit different color spectrums of light. A high pressure sodium bulb produces light that is reddish-yellow, while metal halide bulbs produce a much more balanced white light that has more of the visual spectrum. A metal halide bulb produces about 65-110 lumens of light per watt while a high pressure sodium bulb produces about 96-150 lumens of light per watt.

Both bulbs have a relatively long lifespan, though a high pressure sodium bulb will last slightly longer, up to 6 to 18 months at a usage rate of 12 hours per day (2 to 6.5 thousand hours total), while a metal halide bulb will last for 6 to 12 months at a usage rate of 18 hours per day (3 to 6.5 thousand hours total).

When used by growers, a metal halide bulb is preferred for the earlier stages of a plant’s growth when its vegetation is developing, as this bulb’s light makes it grow with shorter spaces between branches. Later, a high pressure sodium bulb is used since its light is good for flowering and fruiting.

Video

Here is an explanation of the difference between the two bulbs, especially for those who want to use them for gardening: