As with many products, you get what you pay for when buying solar lights. I was always taught that if you buy cheap you buy twice. It is often proved beneficial to pay that little bit extra for a more reliable performance.
Garden solar lights consist of a solar panel (often built in) charging a battery during daylight and then illuminating via LEDs as night falls. The light is switched on when the solar panel is not charging and turns off when the panel starts to charge again at daybreak.
Contrary to popular belief, many solar lights do not have an in-built photocell. Daytime and night-time are sensed by monitoring voltage. When the control module senses a voltage from the solar panel, the light will remain off. This is due to the sunshine charging the battery. When the sun goes down (dusk), the charging ceases and there is no longer a voltage passing through. Only then will the LEDs illuminate. When the sun rises again, charging resumes and voltage is again sensed causing the LEDs to turn off and so on. As you can see, this is a dusk to dawn function but not via photocell technology.
Performance vs Price
The performance of the solar light depends upon the quality of the solar panel, the re-chargeable battery and the LEDs. All have improved significantly in recent years.
If you are happy for the lights to be purely decorative and last not much more than a year, then buy the ones that typically cost from £5.00 to £15.00. If you want something better and lights that are brighter, then pay up to around £50.00. These lights will usually have a 1 year guarantee. The guarantee is often limited due to the rechargeable batteries used not charging up properly after around 18months or less of use. The type of materials used to construct the light may also deteriorate after a time.
Better and brighter lights using the best materials range in price from £50 to over £200. They are usually sold with a 2 or 3 year warranty. This price range also uses higher quality electrical components (LEDs, solar panels, batteries, and control modules).
For the best quality lights always check the light output (lumens, divide by 10 to get an approximate comparison with mains lights), and the type of battery used (Lithium Ion or Lifepo4 lithium batteries should last at least 5 years). Look for a good, reputable company with a UK base and telephone contact. Some companies have a 30-day sale or return policy so that lights can be returned after 30 days if they do not perform as well as expected.
Avoid websites where no information on lumens, battery type or expected lifetime is stated. If this information has been omitted, it is likely that they are of lower specification.
Get the best out of your Solar Lights
Solar lights should be positioned in a non-shady area, preferably south facing and the solar panels kept clean for best performance. A good solar light will light all year. Even on dark winter days and cloudy days it should light for several hours.