Candles are a highly problematic source of light because of their running cost and the fire risk they pose. They are popular because they don’t rely on a support infrastructure and people can stockpile it for hard times.
The initial purchase price of candles is low. This is useful in cash-flow-constrained households, but actual running cost are high. Here is a calculation showing the break-even points between the most basic candle available from one of South Africa’s biggest retailers as compared to the marginal cost of adding the illumination option to an existing Sigthsense device.
The marginal cost of adding the LED lighting option to the most basic fire and flood detector is US$7.50
The most economical candle option from South Africa’s “Pick n Pay” retailer is the “Price’s Classic Candles 8 Pack”. This retails for ZAR18.99 at the time of writing (equivalent to US$1.30).
Burning all eight candles in the pack simultaneously will result in approximately the same level of illumination as a Sigthsense LED light. Typically, these candles burn for around four hours.
Adding the Sigthsense illumination option to the most basic version of the device will cost 5.8 times the price of a pack of candles.
From this we can see that the running cost of candles reaches the price of the LED illumination option after a mere 24 hours. Thereafter lighting is essentially free, allowing the resources previously allocated to lighting to be used elsewhere.