Free light from plastic bottles: it only works in daylight
Drilling a hole in your roof and fitting a water bottle to get free light only works during the day. A look at its limitations, asbestos risks and how it compares to a skylight.
English · Original discussion in Spanish · Published
The plastic bottle that promises free light only works while the sun is out
A trick to light your home without electricity? Maybe, but only if you live in the desert. The idea of drilling a hole in the roof and fitting a water bottle to refract sunlight has been circulating online for over a decade. In theory, it's a low-cost skylight. In practice, its limitations make it a laughable solution for anyone who doesn't live in Arizona.
Why it's useless for most households
The first problem: the bottle needs direct sunlight. With clouds, rain or at dusk, its output drops to zero. In other words, exactly when you need light at home the most. What's more, plastic degrades under ultraviolet radiation, so after a few months the bottle turns opaque and has to be replaced. And beware: if the roof is made of fibre cement containing asbestos, drilling into it releases carcinogenic fibres. That's no small risk.
Compared with a traditional skylight
Compared to an acrylic or polycarbonate skylight, the plastic bottle offers more even light diffusion, but at the cost of lower durability and a higher risk of leaks. Some variants add chlorine to the water so it glows at night, but that effect only lasts a few hours. In short, it might do for lighting a windowless storeroom during the day, but as a substitute for electric light it's a bad joke.
The night-time factor: the great fiasco
The anonymous inventor who came up with this "hack" overlooked one detail: people need light when the sun goes down. With the bottle, after sunset all you get is darkness. That's why the sceptical comments were quick to appear: it's like a motorbike that only works downhill or an air conditioner that only cools in winter.
The sarracena: if you want natural light, fit a window or a skylight. If you want to save on your electricity bill, better invest in solar panels. The plastic bottle will look great on Instagram, but in reality it's a remedy as short-lived as the day itself.
Related discussions in the forum
A trick to light your home without electricity? Maybe, but only if you live in the desert. The idea of drilling a hole in the roof and fitting a water bottle to refract sunlight has been circulating online for over a decade. In theory, it's a low-cost skylight. In practice, its limitations make it a laughable solution for anyone who doesn't live in Arizona.
Why it's useless for most households
The first problem: the bottle needs direct sunlight. With clouds, rain or at dusk, its output drops to zero. In other words, exactly when you need light at home the most. What's more, plastic degrades under ultraviolet radiation, so after a few months the bottle turns opaque and has to be replaced. And beware: if the roof is made of fibre cement containing asbestos, drilling into it releases carcinogenic fibres. That's no small risk.
Compared with a traditional skylight
Compared to an acrylic or polycarbonate skylight, the plastic bottle offers more even light diffusion, but at the cost of lower durability and a higher risk of leaks. Some variants add chlorine to the water so it glows at night, but that effect only lasts a few hours. In short, it might do for lighting a windowless storeroom during the day, but as a substitute for electric light it's a bad joke.
The night-time factor: the great fiasco
The anonymous inventor who came up with this "hack" overlooked one detail: people need light when the sun goes down. With the bottle, after sunset all you get is darkness. That's why the sceptical comments were quick to appear: it's like a motorbike that only works downhill or an air conditioner that only cools in winter.
The sarracena: if you want natural light, fit a window or a skylight. If you want to save on your electricity bill, better invest in solar panels. The plastic bottle will look great on Instagram, but in reality it's a remedy as short-lived as the day itself.
Related discussions in the forum
- Solar ovens and cookers. · 11 replies
- Russian stoves or Kachelofen. · 44 replies
- Penny-pinching on electricity · 19 replies
- Very happy with my LED lights · 99 replies
Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (13 replies).
More summaries
-
O2 offers 10 TB of free cloud storage, but there's a 4 GB catch
O2 is giving away 10 TB of cloud storage in Spain, but with a 4 GB limit per file. We compare it with Digi and Movistar and assess whether it's worth it.
-
Home savings tricks to beat inflation
Analysis of homemade saving tricks and responsible consumption tactics in the face of inflation.
-
The One-Thousand-Euro Trap in Spain: Fixed Costs and Zero Savings
With 120 euros for food and 350 for rent, a Spanish low-wage earner barely survives. An analysis of expenses that leave zero savings and a spiral of precariousness.
-
Tacos el Gordo: when a food video turns political
A video about Tacos el Gordo sparks a heated debate on socialism, North Korea and responsible consumption, with North Korean luxury as the backdrop.
-
Drilling neighbor: a legal guide to getting your peace back
Unbearable noise from a neighbor's drill: dialogue, Spain's Horizontal Property Law, a domestic violence report and skepticism about whether any of it works in Spain
-
How to download Spotify songs as MP3 in 2025
Downloading Spotify songs as MP3 is possible with tools like SpotDL or YouTube. Quality vs convenience: is hunting for FLAC worth it? A look at the methods.