Wake-up light: waking up with a simulated sunrise

When a wake-up light makes sense in the bedroom

The question starts not with the device but with the morning. If you still get up in the dark in winter, a phone alarm pulls you abruptly out of sleep. A wake-up light starts there: it raises the brightness over half an hour or longer, so the room is already light when the sound begins. The principle assumes that your bedroom is really dark beforehand. Street light streaming in or a display that glows all night removes the basis for the effect.

Typical uses are the bedrooms of working people with an early start, rooms with no window or a view onto a wall, and households where two people get up at different times. A wake-up light can be an aid there, but it is not a medical device. Philips says so itself for its devices: according to the manufacturer, the SmartSleep wake-up lights are not medical devices, and Philips names no indication for conditions caused by a lack of light.

An honest note belongs here: we have not run any of these devices in a bedroom ourselves. All information on this page comes from manufacturer documents and product listings and is assessed with no documented hands-on testing. Whether a simulated sunrise helps you get up varies from person to person.

Wake-up light or SAD lamp: the key difference

In everyday talk the two device types are often lumped together, but they do different jobs. A SAD lamp for light therapy works with high illuminance at a documented distance and is used in front of the face during the day. A wake-up light works with warm, weak light right next to the bed and is meant to support waking up. The Philips documents give a maximum of 300 lux for the SmartSleep range, according to the manual at a distance of 45 centimetres. A SAD lamp with 10,000 lux is in a completely different order of magnitude.

A clear distinction follows from this: if you want light therapy during the day in winter, a wake-up light is the wrong advice. If you simply want to wake more gently, you do not need a 10,000 lux lamp by the bed. You can find the detailed comparison in the article SAD lamp or wake-up light, and the assessment of light therapy itself is in the guide Using a SAD lamp correctly.

Health note: Light therapy does not replace medical treatment. For persistent sleep disorders, a lastingly low mood or suspected seasonal depression, medical advice is necessary. A wake-up light is no substitute for that.

What matters when choosing

Wake-up lights can be compared through a few features. The following list shows the points that are actually documented in the manufacturer documents.

• Sunrise duration: For the SmartSleep models it can be set from 20 to 40 minutes according to the manufacturer, the HF3651/01 runs over 30 minutes according to Philips, and the LIORQUE SM-02 up to 60 minutes according to the listing.
• Brightness: Philips gives a maximum of 300 lux with 20 brightness settings (HF3651/01: 315 lux with 25 settings). The SM-02 has no lux figure, but it does have a product data sheet with 185 lumens of useful luminous flux at 3.5 watts.
• Second way of waking: Sound, radio or both. This matters in case the light alone is not enough.
• Charging port: Only some models charge the phone on the bedside table.
• Display and night mode: A self-dimming or switchable display prevents stray light in the bedroom.
• Dimensions and weight: According to Philips, the SmartSleep models are just under 20 centimetres in diameter and need a corresponding amount of room on the bedside table.

On colour: the manual for the SmartSleep range gives roughly 1,500 to 2,800 kelvin for the colour temperature, that is, deliberately warm light. What kelvin means in everyday terms is explained in the article Colour temperature and kelvin.

The Philips models at a glance

Philips is represented in this segment by several closely related models. According to the manufacturer, the light is the same across the three SmartSleep variants: 20 brightness settings, a maximum of 300 lux, a coloured sunrise from red through orange to yellow, and a sunset function. The differences lie in sound, radio and charging port.

According to the manual, the Philips SmartSleep HF3532/01 has no radio, but it has seven natural alarm sounds and a USB charging port with 5 volts at 0.5 amps. This is the variant to choose if you want to charge your phone at the bed overnight. The only documented difference from the sister model HF3531, which has no product page of its own with us, is the missing radio. Both models have the USB port.

The Philips SmartSleep HF3521/01 relies on an FM radio and six natural alarm sounds, but according to the data sheet it does not charge an iPhone or an iPod. It suits you if you want to listen to the radio in the morning and do not need a charging port. As an alternative to the HF3532, it is therefore no step back in light, just a different equipment package.

According to the data sheet, the Philips Wake-up Light HF3519/01 gives 300 lux as the maximum, 20 brightness settings, an adjustable sunrise of 20 to 40 minutes, five natural alarm sounds and an FM radio. Philips lists it as a wake-up light and not as a medical device. It has fewer alarm sounds than the other two SmartSleep models, but the light function matches the range.

The Philips Wake-up Light HF3651/01 is a model of its own with somewhat different data: according to Philips 315 lux as the maximum level, 25 brightness settings, a sunrise over 30 minutes, eight alarm sounds, FM radio, AUX input, night light and a charging function for mobile phones. The data sheet gives the dimensions as 225 by 220 by 120 millimetres at 0.9 kilograms including the adaptor. The Amazon listing differs from this with 12 by 19 by 19 centimetres, so you should measure your bedside table against the manufacturer's dimensions.

Other designs: sound programmes and kids' devices

Not every wake-up light is a Philips device. According to the listing, the LIORQUE SM-02 wake-up light brightens over up to 60 minutes and offers 20 melodies and 10 white noise options in 30 volume levels as its second way of waking. The display can be dimmed in 5 levels and switched off completely. There is no lux figure, but there is a product data sheet under Regulation (EU) 2019/2015: 185 lumens of useful luminous flux at 3.5 watts in class G. It is therefore an alternative to the Philips models if a switchable display and a longer wake-up duration matter to you.

For a child's room, a classic sunrise alarm clock is usually not the right principle. According to the manufacturer's instructions, the LIORQUE kids' alarm clock with sleep trainer works with a sun and moon symbol: green means get up, blue means sleep. It is expressly not a wake-up light with sunrise simulation. Documented are three brightness levels for the light, six ringtones, seven soothing sleep sounds, a timer function with 15, 30 and 60 minutes and a built-in rechargeable battery. More on this is in the article Wake-up light for kids.

Comparison of the models mentioned

The table summarises the information documented on the respective product pages. All values are manufacturer figures (or figures from the listing) and have not been measured by us.

The lux figures are comparable only within the Philips range. For the HF3651/01, Philips gives no measuring distance, so the figure of 315 cannot cleanly be set beside the 300 lux of the SmartSleep range at 45 centimetres. The SM-02 value is a luminous flux in lumens and therefore a different quantity from illuminance.

Which device suits whom

The documents point to a few situations that can be described without ranking them.

• You want to charge your phone at the bed: the Philips SmartSleep HF3532/01, the Philips Wake-up Light HF3651/01 and the LIORQUE SM-02 wake-up light list a charging port or a charging function (for the SM-02, 5 watts according to the listing).
• You want to listen to the radio in the morning: the Philips SmartSleep HF3521/01, the Philips Wake-up Light HF3519/01 and the Philips Wake-up Light HF3651/01 have an FM radio.
• You want the display completely dark at night: the LIORQUE SM-02 wake-up light can be switched off entirely according to the listing, the display regulates itself on the Philips models HF3521/01 and HF3532/01, and no information is available for the HF3651/01.
• You want a longer wake-up duration: the SM-02 gives up to 60 minutes, the Philips models 20 to 40 and 30 minutes respectively.
• You are looking for something for a child: the LIORQUE kids' alarm clock with sleep trainer is a sleep trainer and not a sunrise alarm clock.

If you are not yet sure which light source suits your bedroom, the lighting calculator helps you assess the room and the task. An overview of all devices in this category is given in SAD lamps at a glance. For the link between light and sleep rhythm, read the guide Light and sleep.

Limits and pitfalls of wake-up lights

A wake-up light is no guarantee of a relaxed start to the day. It works only together with a dark room, a regular bedtime and a device that suits being operated half asleep. For devices with touch controls, much depends on whether you can hit snooze and off reliably. We have no documented measurement on this. With no documented hands-on testing, this remains a question you can check before buying using the published operating instructions.

It is also worth looking at mains dependence. The documented devices run on the mains. On the SM-02, the built-in rechargeable battery serves, according to the listing, to store the settings and not for operation away from the mains. For the Philips SmartSleep, the data sheet gives a clock backup of 4 to 8 hours for power cuts. If you depend on reliable waking even during a power cut, you should have a second alarm clock as well.

The usual caution applies to electrical devices at the bed: do not kink the cable, do not cover the power supply and follow the manufacturer's instructions. If you have lasting problems falling asleep or waking up, you should not hope for another device but seek medical advice.