Solar Irradiance Meter vs Lux Meter for Solar Panel Testing Malaysia
Solar Irradiance Meter vs Lux Meter for Solar Panel Testing Malaysia
Can you use a normal lux meter to measure sunlight for a solar panel?
A lux meter and a solar irradiance meter may both respond to light, but they measure different quantities and are designed for different measurement purposes.
For solar PV work, understanding this difference is important when selecting the correct instrument.
Lux meter → measures illuminance in lux
Solar irradiance meter → measures incident power per unit area, typically in W/m²
For technicians who need portable solar radiation measurement, the VICI LX-107 Solar Power Meter is designed for solar power and solar radiation applications.
What Does a Lux Meter Measure?
A lux meter measures illuminance.
Its result is expressed in:
lux (lx)
Illuminance measurement is widely used for applications such as:
Office lighting
Factory lighting
Warehouse lighting
Classroom lighting
Workplace illumination
Indoor lighting assessment
Building lighting
General lighting inspection
Lux is therefore extremely useful when the objective is to evaluate illumination.
However, that does not make it the same measurement as solar irradiance.
What Does a Solar Irradiance Meter Measure?
A solar irradiance or solar power meter measures incident power over an area.
The measurement is commonly expressed as:
W/m² – watts per square metre
This makes it directly relevant when technicians want to quantify solar radiation reaching a PV module or another surface.
Applications can include:
Solar PV installation
Solar panel inspection
Solar radiation measurement
Rooftop PV maintenance
Solar research
Meteorological applications
Agricultural studies
Window and glass evaluation
Solar Irradiance Meter vs Lux Meter: Quick Comparison
Measurement Quantity
Lux Meter: Illuminance
Solar Irradiance Meter: Incident solar power per unit area
Typical Unit
Lux Meter: lux (lx)
Solar Irradiance Meter: W/m²
Common Application
Lux Meter: Lighting measurement
Solar Irradiance Meter: Solar radiation measurement
Solar PV Relevance
Lux Meter: Not a direct measurement of solar irradiance
Solar Irradiance Meter: Directly provides a W/m² solar radiation measurement
The correct instrument depends on what the technician actually needs to know.
Why Are Lux and W/m² Different?
The difference comes from what is being measured.
Lux is based on illuminance and is related to the response of human vision.
W/m² describes physical radiant power incident over an area.
Therefore, two measurements should not simply be treated as interchangeable.
A lux value should not automatically be converted into an accurate solar irradiance value using one universal conversion factor.
The relationship depends on the spectral characteristics of the light source and measurement conditions.
For PV work, if the required parameter is solar irradiance, it is better to measure that parameter directly with an appropriate instrument.
Which Meter Should I Use for Solar Panel Testing?
If the question is:
“How bright is this workplace?”
Use an appropriate lux meter.
If the question is:
“How much solar power is reaching this PV module?”
A solar irradiance meter measuring W/m² is the more relevant instrument.
This distinction becomes important when technicians are trying to interpret PV electrical performance.
Example: Factory Rooftop Solar Inspection
A maintenance technician is investigating a factory rooftop PV system.
The DC output appears lower than expected.
A normal lux reading may tell the technician something about illuminance, but the PV investigation needs information about the solar radiation incident on the modules.
A solar irradiance meter can provide:
Solar irradiance: ___ W/m²
The technician can then record this together with:
DC voltage: ___ V
DC current: ___ A
Module temperature: ___ °C
Time: ___
Weather conditions: ___
This provides a more relevant set of measurements for PV troubleshooting.
Why W/m² Matters During PV Inspection
PV output changes with environmental conditions.
If solar radiation is weak, electrical output may also be reduced.
This means:
Low PV output + low irradiance
should not automatically be interpreted in the same way as:
Low PV output + relatively strong irradiance
Measuring W/m² gives technicians additional information before they investigate other potential causes.
Can an Irradiance Meter Diagnose a Faulty Solar Panel?
No.
A solar irradiance meter answers one main question:
How much solar radiation is present at the measurement point?
It does not independently determine whether a module, inverter, connector or cable is faulty.
Depending on the problem, additional instruments may be required for:
DC voltage
DC current
Insulation resistance
Temperature
Thermal imaging
Earth resistance
PV-specific electrical testing
Solar irradiance is one part of a broader diagnostic process.
VICI LX-107 Solar Power Meter
The VICI LX-107 is a portable solar power meter designed for solar radiation and related measurements.
The instrument provides functions including:
W/m² Display
For solar power measurement per unit area.
BTU Display
Provides another measurement unit for relevant applications.
MAX / MIN
Useful for observing changes during a measurement period.
Data Hold
Allows the user to hold a displayed value for convenient recording.
According to VICI, applications include solar installation, solar radiation measurement, solar research, physics and optical laboratories, meteorology, agriculture, industrial applications and high-performance window identification.
When Should You Buy a Lux Meter Instead?
A lux meter remains the correct choice for many applications.
For example:
Factory Lighting
Checking illumination at production areas and workstations.
Office Lighting
Evaluating lighting conditions at desks and work areas.
Warehouse Lighting
Checking illumination in storage and operational zones.
Schools and Laboratories
Measuring lighting conditions for visual tasks.
Building Maintenance
Assessing indoor lighting performance.
If the requirement is illumination, buy a lux meter.
If the requirement is solar radiation in W/m², select an appropriate solar irradiance or solar power meter.
Do Solar Installers Need Both?
Potentially, but for different jobs.
An electrical or solar contractor may encounter both lighting and PV applications.
A lux meter can support lighting-related work.
A solar irradiance meter can support solar radiation measurements.
There is no need to force one instrument to perform a measurement it was not designed to provide.
Solar Irradiance Meter for Rooftop PV
For rooftop solar inspection, a portable irradiance meter can be used to record sunlight conditions during:
Installation
Inspection
Preventive maintenance
Troubleshooting
PV performance checks
Comparison between measurement locations
For useful results, technicians should consider sensor orientation, shading, changing weather and measurement timing.
VICI LX-107 for Solar Installers Malaysia
For Malaysian solar installers and maintenance technicians requiring straightforward portable W/m² measurement, the VICI LX-107 Solar Power Meter can provide a practical field measurement option.
Its handheld format also makes it convenient for moving between different locations on residential, commercial and industrial rooftops.
More advanced PV commissioning or diagnostic work may require additional specialised instruments.
Choosing Between a Lux Meter and Solar Irradiance Meter
The easiest way to choose is to start with the parameter you need.
Need to measure workplace brightness? → Lux Meter
Need solar radiation in W/m²? → Solar Irradiance Meter
Need PV voltage/current? → Appropriate electrical or PV tester
Need module temperature patterns? → Thermal imaging or appropriate temperature instrument
Selecting equipment by measurement requirement helps avoid purchasing the wrong instrument.
Solar Irradiance Meter Supplier Malaysia
MTM Precision supplies testing and measurement instruments for:
Solar installers
Electrical contractors
Factory maintenance
Facility management
PV maintenance companies
Engineering companies
Universities and laboratories
Industrial users
The VICI LX-107 Solar Power Meter is suitable for enquiries where users require portable solar radiation measurement in W/m².
Contact MTM Precision
MTM Precision Sdn Bhd
Website: www.mtmpre.com.my
Email: mtmpre@yahoo.com
WhatsApp: 016-660 7346
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Serving customers throughout Selangor, Kuala Lumpur, Johor, Penang, Perak, Negeri Sembilan, Melaka, Pahang, Kedah, Perlis, Terengganu, Kelantan, Sabah and Sarawak.
Not sure whether you need a lux meter or solar irradiance meter? Contact MTM Precision with your application and measurement requirement. We can help identify the appropriate instrument for your work in Malaysia.
08 Sep 2026
