5 Things to Know Before Buying best street light

Twenty years ago, solar energy could only appear in books or movies for ordinary people. Now, in 2020, solar energy has been widely used in industrial power generation, residential power generation, solar lighting, solar water pumps, etc. Especially this year, due to the epidemic, the price of solar panels has dropped to about US$0.18 per watt. 

However, in 2019, the solar panel’s price needs to be US$0.3 per watt, which is currently the lowest in history. And people can easily buy various residential solar lights on Amazon such as solar garden lights, solar flood lights, solar security lights, and solar wall lights. Solar street lights are also common in various roads and public lighting places. The price of solar lights can be as cheap as tens of dollars or as expensive as hundreds of dollars. The solar lamp with dozens of dollars is used in the home, the brightness is low, the lighting time is short, and the life span is about one year. And hundreds of dollars of solar street lights are used in public lighting, which can hit thousands of lumens, stay on all night, and can work for 3 to 5 years or even more than 5 years. 

When we buy solar lights, especially when buying solar street lights for government projects, we should pay attention to a few misunderstandings that are easy to make mistakes. Some misunderstandings are because of the customers’ understanding, and some are deliberately created by suppliers to confuse customers. The suppliers need to get orders from the customers while they also need enough profits.

However, the end customers mostly will find problems with the solar street lights they buy. So in this article, we listed 7 misunderstandings when purchasing solar lights, and also explained the technical reasons for these misunderstandings.

 

Misunderstanding 1: Led quantity is equal to led power

Here we can give you the correct conclusion directly: Led quantity does not mean the same led power. 

In the description of most solar lights shop in Amazon, the led quantity is a key specification of the solar lights. Seem more led quantity means bigger power. Somehow, Led power can be set by the solar charge controller of any power to zero. The power of one led chip can be different from 0.2 Watt to 5 Watt or even more. Like the 2835 SMD led chip is 0.2 Watt, Phillips 3030 SMD is designed 0.3-1 Watt, and Phillis 5050 SMD can be set 5 Watt per piece as the highest. 

And the price of different led chips with a different brand can also be different from $0.002 to $0.2 (example). So you can find easily that the led quantity can not be the key point of the solar lamp’s power nor does it represent the cost of solar lights. The same mistakes always happened to the solar street lights bids in the Philippines. In the solar street lamp parameter requirements, the number of LEDs is usually required to be no less than a number.

Misunderstanding 2: Led power is equal to the brightness

 As the third-generation light source led can save more power to keep the same brightness. We calculate the brightness by the lumens(lm) but not the wattage. Because the brightness is decided by the luminous efficacy (lumens per wattage). 

The luminous efficacy of the electric incandescent lamp is 12-24 lumens per wattage only. And the Compact Fluorescent Lamp fixtures can reach 50-60 lumens per wattage. And led can generate more lumens per watt (lm/w). Then the led lights fixtures in 2010 can reach 100-110 lumens per wattage. 

In the market 2020, different types of led can generate different luminance efficacy (lm/w). Some led chips can reach more than 200lm/w, some can be only 130lm/w around. So the best to calculate the brightness is not by led power, but by the lumens.

In the summary of misunderstanding one and misunderstanding two, here we also want to remind that the solar lights led power is always labeled much higher than the real led power. 

Take the solar flood lights in Amazon shop, for example, they have labeled 100 wattage solar floodlights, 200 wattage solar flood lights, and 300 wattage solar floodlights. The so-called 300watt solar flood lights, real led power is 15 watt at the highest. Because you can easily find that the solar panel power of it is only 25watt to 30watt. How can such a small power solar panel can support 300Watt led to power long time lighting? No more than one hour! Another key material is the battery, it is 3.2 voltage battery. As we mentioned previously, a 3.2 voltage system can support led power no more than 20watt. So if you deal with serious solar street lights projects for government, the key specification is not led by power but also the luminous efficacy of the whole solar light fixtures.

 

Misunderstanding 3: Judge the charge controller quality by the current simply.

The key to judging the charge controller quality is the charge controller’s broken rate in mass order. The 10A or 15A current of the controller is just to make sure the controller can drive enough solar panel power in a given voltage. And the quality of the charge controller is mainly decided by the technical accumulation from the real projects by Debugging and updating the hardware and software from the real problems. The cost of the solar charge controller is small in outdoor solar lights.

Misunderstanding 4: Solar panel sizes equal to the solar panel power

The solar panel can use less solar cell quantity to make sure the outlook and size of the solar panel the same. And some solar street lights factories will make not enough solar panel power to save the cost to get some orders. To make more profits, some factories will deliberately put broken solar chips in the solar panels to achieve sufficient size. Or they will use grade B or grade C solar cell which life span is very short.

Regarding solar panels, we would like to add one suggestion. Use monocrystalline solar panel but not the polycrystalline solar panel for the project using solar street lights. Because monocrystalline solar panels can get bigger power than the polycrystalline solar panel in cloudy days. And the led lighting time in the cloudy day is the key quality for the street lighting. Another reason the size of the monocrystalline solar panel can be 20% smaller than the polycrystalline solar panel in the same power. And the solar street lights need to be installed on top of the pole. Smaller weight and size of the solar street lights will make the installation easier and safer.

Misunderstanding 5: Battery capacity is AH

The battery capacity is voltage multiplied by AH. Some customers just request the ah of the battery. It is not enough, we also need to know the voltage of the battery. For instance, the 12 voltage 30ah battery is a 4 times capacity of 3.2 voltage 30ah battery. 

Normally, small power solar flood led lights and the small power solar wall lights which are hot sales in Amazon and eBay are 3.2 voltage system batteries. But low voltage battery systems can not support big power led solar lights. Because smaller voltage, bigger currency needs to be set to reach the power wattage. Big currency needs thicker wire and will make the solar charge controller easy to be broken. As our experience, a 3.2 voltage battery system supports solar lights led power that no more than 20 wattages. However, led power under 20 watt, we advise using a low voltage system. Because the cost of the 3.2 voltage battery is much lower than the 12 voltage battery which needs a more complicated packing to precess. And the cost of the 3.2 voltage solar charge controller is also smaller than the 12 voltage controllers.

 

Misunderstanding 6: Led chip is very expensive

Here we must point out that the solar light has four main accessories. They are Solar panel, battery, Solar charge controller, and light source. A solar cell is a component that generates electrical energy by converting solar energy into electrical energy. 

Compared to polycrystalline solar modules, monocrystalline solar modules have higher efficiency and lower production costs than polycrystalline modules. There is no reason to recommend monocrystalline solar cells for solar lights, but there are some reasons for the high cost and low efficiency of polycrystals. 

Batteries are the energy storage devices in a solar system, but solar cells cannot store energy, so the solar lamp goes out immediately when a battery is present. Lithium batteries have a much longer life and less weight than lead-acid batteries. 

But lithium batteries are more expensive for the same amount of energy than lead-acid or lithium batteries. 

Solar chargers are the brains behind solar lights, and public lighting as a whole is growing rapidly, so the cost of batteries can fall sharply. 

Currently, batteries are more expensive than lead-acid batteries, but not as expensive as lithium batteries. This allows the electrical energy generated by solar cells to be charged in a battery – safely, protected from the sun, wind, rain, or other sources of solar energy. LED is undoubtedly the only source of light for solar lamps and has the highest luminosity. Besides, solar charge controllers can be realized due to the low cost of lead-acid batteries, so that they can control the brightness of the lamp, which can be either dark or weak. LEDs with the same brightness can be used to save the total cost of the solar light. Compared to solar cells and batteries, LED removes the low-

The main cost of the solar street lights is the battery and solar panel. And the cost of the battery is the best in solar lights. Led take part 5% to 10% cost of the whole solar lights. So battery quality is the most important thing for solar lights purchasing. To lower the cost of the whole solar street lights fixtures cost, we advise using high luminous efficacy led chips which can reach more than 220 lumens per watt in 0.8 watts per piece. So that we can use lower led power to reach the same brightness and we can set lower wattage solar panels and smaller battery capacity to get the cheapest solar street lights. 

Take the 6000 lumens all in one solar street lights for example, if we use 150 lumens per watt led solution, we need to set 70 watts solar panel and 12V 30AH lithium battery. If we use 200 lumens per watt led solution instead, led power can be 30 watts only. Then we can low down the solar panel power to 50 watts and lithium battery to 12V 22ah. The material cost of the 6000 lumens solar street lights can low down 15% around.

Until now, the expensive cost of the projects using solar street lights is the main reason to limit the high power solar lighting market demand. And we can imagine that the day that the battery cost low down to a very low level will be the day that the solar street lights are installed all around the streets. 

Misunderstanding 7: The sample solar lights work well means Solar street lights quality is good

The solar lighting system is more complicated than the led lights because of the solar charge controller and battery. Sometimes, the sample of solar lights works well. But in mass orders, if the quality of the controller and battery is not good, the broken rate of the solar street lights will be very high.

And the 3 key points to judge the quality of the solar lights are the brightness（lumens), the lighting time in the night, and the cloudy days and the life span. The main material that determines the life of solar street lights is the lithium battery. Once the battery capacity is not big enough or the battery is not good quality, the life span of the solar lights can be no more than one year. So the samples can work well in several months but its lighting time will drop down later in one year.

 

Wondering about what is better between LED and HPS street lights? Here’s a fresh, detailed and updated evaluation you are looking for.

 

Left: https://www.shutterstock.com/image-photo/dark-back-alley-under-sodium-street-1219175203

Right: https://www.shutterstock.com/image-photo/night-street-quiet-residential-quarter-795193015

So you are not a lighting engineer or a horticulturist to have an instinctive ability to know the best requirements for outdoor lighting. But you need to know if buying the new LED lighting luminaire justifies its upfront cost. Is it really better than the old sodium street lights you’ve grown up with?

Today, solar LED street lights are mainstreaming worldwide. Everyone wants to shift to greener alternatives, zero electricity costs and less carbon footprint.

So whether you’re an expert lighting professional, a contractor, a building manager or a homeowner wanting to know more about LED lighting versus HPS lighting, this article is for you.

In this blog, we have laid out the differences in characteristics, performance, efficiencies, costs and warranties of LED and HPS street lights. Read on!

What is a High Pressure Sodium (HPS) Street Light?

High Pressure Sodium (HPS) street lights are one of the most common street lights you can see today. They produce a distinctively yellow-orange, monochromatic glow.

You can still see many HPS lights for lighting large areas, manufacturing sites, roadways, parks, and parking lots. They are also commonly used as grow lights for plants. But today, HPS street lights are quickly being retrofitted with more efficient and eco-friendly LED lights.

What are the Advantages of an HPS Street Light?

If you’re wondering why a lot of HPS lights haven’t been taken down today, this is because they still present some benefits to the community. Here they are.

• Among the other types of street lights, HPS is the most efficient (about 7 times more than incandescent lights, 2 times more than mercury vapor lights).
• Quicker warm-up time than other lamp types (3 to 4 minutes) like mercury vapor and metal halide.
• Longer lifespan (24,000 hours).
• Cheaper price
• Higher lumen efficiency than older street light types.
• Wide variety of lighting brightness and power ranging from 35 to 1000 watts.
• Great for growing plants.

What are the Disadvantages of an HPS Street Light?

But HPS street lights don’t come entirely clean. Here are the drawbacks.

• Does not accurately reflect the true color of objects.
• Needs a transformer/ballast for voltage and current regulation to assist start up and operation.
• Requires a few minutes (5 to 10 minutes) before reaching full light brightness.
• Needs one minute to cool down.
• Produces reddish color at the end of its life
• Burns at the end of its life.

Now let’s move on to the newest type of street lighting today.

Best Uses of HPS Street Lights

Since HPS street lights have high intensity lights, they are best for tall mounting applications like for industrial lighting and security lighting. They are the best options when you need to mount street lights with 15 feet and above heights.

They are not suitable for applications needing high color rendition accuracy, like in retail and commercialize lighting. HPS lights would do poorly on projecting the colors of objects with high precision. If street lights are to be switched on and off frequently, HPS lights are also not appropriate for the job. This is where LED street lights are best at.

What is a Light Emitting Diode (LED) Street Light?

https://www.shutterstock.com/image-photo/outdoor-led-lighting-562099690

An LED street light is a better street lighting option which is highly preferred in today’s struggle towards green living. This is because integrated LED street lights are more energy-saving than other outdoor lights, requiring less maintenance and operation costs.

In fact, they are 50% more efficient than traditional sodium street lights, and can last 20-25 years. This is why majority of the world are shifting towards LED outdoor lights.

LED lamps produce a distinct bluish white glow. Newer LED street lights can produce amber-colored hue or yellow-warm colors which are more animal-friendly with the least light pollution.

What are the Advantages of LED Street Lights?

• Longest lifespan compared with other street light types (50,000 to 100,000 hours)
• Least heat emission
• Directional light (over 180 degrees, unlike other lights with 360 degrees light direction)
• Easy warm up, and switching on and off
• Doesn’t emit ultraviolet rays unlike HPS
• Low maintenance costs
• Low operation cost
• Used for smart solar street lights, where brightness can be automatically adjusted

What are the Disadvantages of LED Street Lights?

• A little expensive upfront

Best Uses of LED Street Lights

LED street lights are best outdoor lighting applications requiring high color rendering accuracy. They can be used for both retail, commercialized and industrial lighting.

Today, you can find solar street lights, smart integrated LED street lights, All-in-One solar street lights and adjustable LED street lights the best choices for smart, energy efficient and low cost solutions.

Smart LED street lights are equipped with automatic dimming and brightness and you can set different lighting modes depending on your area’s requirements. They are also highly recommended for parks, parking lots, roadway lighting, pathway lighting, pedestrians, gardens, and many more.

Difference Between LED and HPS Street Light

Here, we present the different characteristics of HPS street lights and LED street lights.

LED and HPS Showdown

Key Interest

Description Criteria for Street Lights LED Street Light HPS Street Light

Verdict

Color Rendering Index (CRI)

CRI is how the light source reflects the color of an object, showing its aesthetics and form. 

75-100: Excellent

65-75: Good

55-65: Fair 

0-55: Poor 

65 to 95

20 to 30

LED has a pleasing CRI range, which means light can clearly illuminate/project the colors of objects

Correlated Color Temperature (CCT)

CCT measures how warm or how cold the lighting is. It is expressed in Kelvin (K). 

For Street Lights, AMA recommends a CCT value of around 3000K.

For Flood Lights, it may range from 5000K to 6000K.

Basis: 2000K -warm yellow; 3000K -warm white; 6000K -white; 6500K -cool white

2200K to 6000K

+/-2200K

In term of CCT variety, you have more options with LED than HPS.

ON/OFF

Cycling describes how fast the street light responds to being switched on and off. 

This is where we account the warm up and cool down of street lights.

Faster warm up time and cool down/restrike time is better.

No warm up or cool down

Short delay in turning off and on

LED street lights are better.

Warm Up Time

Instant turn on

1 to 15 minutes

LED

Restrike Time

Instant switch off

4 to 5 minutes

LED

Dimming

The ability of a street light to adjust in brightness when not in use.

A larger dimming range is preferred as it’s a way of saving on energy consumption at certain times when the street light is not in use at night.

Can have automatic dimming functions from 100% to 30% to 0.5%

Dimming requires a ballast; can be dimmed up to 50%

LED street lights have a larger dimmability range and don’t require special ballasts.

Directionality

The ability of light to focus in one direction.

Street light focusing in one direction is highly desirable. 

LEDs illuminate light at only 180 degrees.

Sodium lamps emit light in all directions (360 degrees). 

Hence, a reflector is needed to redirect the light downward, reducing the light’s illumination efficiency.

Outdoor LED street lights illuminate roads more efficiently than sodium street lights because they are highly directional.

Efficiency

It’s the ability of light to illuminate more brightness at less energy and is measured in lumens per watt.

Best to use higher efficiency light types to offset lesser maintenance and operation cost.

114 to 160 Lm/W

80 to 140 Lm/W

Integrated LED street lights are more energy efficient.

Efficiency Droop

It’s the tendency of lights to lose efficiency at high currents, raising heat emission.

Least efficiency droop is better. You can simply feel this when there is less heat emitted at longer periods of lighting.

Has low efficiency droop up to its end of life. The lowest efficiency of LED is only at 80%.

At half of its life (12,000 hrs), HPS emit 90% of its efficiency. At the near end of its life (24,000 hrs), HPS emits 80% of its efficiency.

LED and HPS perform well up until the end of their lifespans. 

But remember, LED lights have a longer lifespan than HPS lights.

Foot Candles

Foot candle

describes the  intensity of a uniform lighting or illuminance of source reaching a 1ft^2  area. 

It gives us an idea if the light is producing uniformity or if unwanted hot spots and dark spots are produced. 

Foot candle also determines if there is an adequate lighting level for outdoor spaces.

Basis:

(lumen/sq.ft)

Freeways: 0.6 to 1.1

Local (commercial, residential): 0.4 to 0.8

Pedestrian/bicycle ways: 2

Alleys(commercial, residential): 0.3 to 0.6

Minor Arterials: 0.7 to 1.4

Parking: 5

LED can better attain the foot candle needed for a desired area at a lesser energy consumption than other traditional lights.

Since HPS street lights are omnidirectional, a large amount of energy needed and redirected just to attain the appropriate foot candle for a desired area. This also means there’s more energy consumed just to attain the proper illuminance of an outdoor area.

LED

Visible Light Emissions

The ability of the light emit visible/optical light, safe and healthy for the human eye and animal vision.

The light emission must play along the spectrum of visible light (range of 400–700 nm) without reaching the wavelengths of UV or infrared values.

For  commercial LED, the visible light wavelength ranges from 360 to 950 nm.

Visible light wavelength for HPS is near 589 nm.

Both LED and HPS are within the spectrum visible to the human eye, but LED has a stronger light emission.

Infrared

none

none

Ultraviolet Mercury Content

Mercury contributes to the lamps efficiency and lifespan, but is harmful when exposed to the environment. That’s why the RCRA and UWR regulates the proper disposal of lamps at the end of its life.

Ideally, lights should have minimal to no mercury content so waste disposal is more convenient and no harmful chemicals are emitted in the environment.

0 mg, no mercury content

6mg per 100 Watts

With LEDs, you can assure there’s no mercury leakage in the environment upon disposal.

Heat Emissions

Heat emission is an energy inefficiency of a lighting system.

Ideally speaking, a lighting system is better if it has minimal to zero heat emission. So the lower heat emission, the more energy efficient is the outdoor lighting system. 

LEDs do not emit heat as other street light types. This is because it is energy efficient. But it still needs a heat sink like any other electronics to prolong its life.

More heat emission. The ballast may either absorb it or be lost in the environment. 15% are likely to be lost by an HPS street light.

LED

Cold Tolerance

The ability of the street light to withstand extremely low temperatures.

High heat tolerance is desirable for cold areas such as Canada, Germany, etc.

-40 Degrees Celsius

-40 Degrees Celsius

LED and HPS can still work at low temperatures, but LED can flick on more instantaneously.

Heat Tolerance

The ability of the street light to withstand extremely high temperatures.

High heat tolerance is desirable for deserts and areas with tropical climates.

75 to 100 Degrees Celsius

65 Degrees Celsius

LEDs have a higher heat tolerance. This makes it more ideal for desert roadway lighting.

Shock Resistance

Indicates how well street lights react to mechanical shocks or wind force.

Since street lights are outdoor lights, they are exposed to harsh conditions. Durable lighting options are therefore preferred.

LED lights are solid state lights (SSLs). Hence they are not easy to damage with any physical shocks.

Fragile as they use glass bulbs

LED

Failure Characteristics

This describes the potential failure points of a street lights before the end of its life.

When LEDs dim gradually, it indicates that it’s nearing its end of life. An LED street light usually has a number of emitters in a single luminaire. So when one diode fails, that doesn’t mean the whole LED module should be replaced.

When HPS reaches its cycling phenomenon, the light flickers on and off before failing.

LED

Life Span

Describes the number of hours the light can be rendered useful.

Longer street light lifespans are better to minimize maintenance and operation costs.

25,000 hours to 200,000 hours

10,000 hours to 24,000 hours

LED has a longer lifespan, but we cannot ignore the fact that HPS lights have a longer lifespan than other traditional lights as well.

Warranty

LED street light manufacturers usually give a 3 to 5-year warranty.

1 to 4 years typical warranty

LED street lights have longer warranty.

Upfront Costs

This accounts the cost of installation, maintenance and operation of your street lights. To know more about cost analysis of street lights, you can see our blog “ How Much Does All-in-One Solar Street Light Costs

The lower total cost is of course the more desirable option.

Typical 100W costs $8 to $13

$5 to $10 for 100W

HPS costs less upfront.

Maintenance

No maintenance cost

Frequent equipment replacements accounts for labor cost, and tooling costs and repair costs 

LED

Lifetime Costs

According to our calculation, it can cost you

$8990 in 10 years.

According to our calculation, it can cost you

$16,710 in 10 years.

LED

Can You Replace High Pressure Sodium Bulb With LED Bulb?

https://www.pinterest.ph/pin/221169031672597812/

Yes you can! You simply need to know the wattage of the existing HPS light bulb and know the amount of light brightness in lumens. Then find an LED bulb that can deliver the lumens required.

Here’s a sample High Pressure Sodium to LED Conversion Table:

 

Lumens Needed

(LM)

Power Draw in Watts HPS

LED

4,500-6,000

100

30-40

6,000

125

40

7,500-9,000

150

50-60

9,000

175

60

11,250-12,000

250

75-80

15,000

320

100

18,000-22,500

400

120-150

For example, you have a 400W HPS light bulb and you want to replace that with an LED light bulb. This means, you can use a 120 Watt LED bulb with 18,000 lumens to replace your 400W HPS light bulb.

To know more about LED retrofitting options for a specific outdoor lighting application, see our “Which Type of Street Lights is the Best for Your Retrofit Project” article.

To know more about other traditional street lights and their alternative outdoor LED light option, see our “12 Types of Street Light Bulb for Any Outdoor Lighting Illumination” blog.

Conclusion

From the above analysis, we can now conclude that LED street lights are far better than HPS street lights in a ton of ways.

Cost efficient. Check!
Higher and faster ROI. Check!
Energy efficient. Check!
No apparent pollution created. Check!
Smart, innovative and convenient. Check!

Did this definitive analysis enlightened you to switch to outdoor LED lights? Are you willing to replace your existing high pressure sodium street lights with LED street lights?

If yes, do not hesitate to contact us to give you the best street light options for your neighborhood, area or municipality. At HeiSolar, we design, manufacture and ship budget-wise and quality-wise solar LED street lights, solar LED garden lights, solar LED floodlights and many more.