No local source for a photodiode which is sensitive to visible light. Time to shop on-line for a photodiode which is sensitive to red light, which will be listed as 650 nm, is directional and can deal with the amount of red light from the electricity meter LED. Reading specsheets for photodiodes is also new to me. I found a webpage with lots of explanations about LEDs and calculations. But, ordering a component on-line which costs less than a euro is a bit silly, with probably a lot more costs in shipping and handling. Conrad just charges extra for too small orders.