Sunday, 21 August 2011

Calculator: Cost comparison of Incandescent vs CFL vs LED globes

Thanks to Chris from and Mitra Ardron for extending the analysis by taking inflation into account – I have modified the calculator for South African (Cape Town) conditions: price of electricity, the price of the globes, and the inflation rate of power costs.

LED (Light Emitting Diode) globe, CFL (Compact Fluorescent Lamps), and the bad old fashioned incandescent globe

To quote Mitra:

The spreadsheet tracks the cost curves for Incandescent, CFL and LED globes so you can see at what point you would break even. 

has changed the figures for South Africans: electricity cost per kWh, and prices for the different types of bulbs
Based on a set of assumptions (that I got from Mapawatt), it shows (at 4 hours/day usage):
* CFL's are better than all of them from year 1, it takes 17 years for LED's to beat CFL's but then need replacing after year 35. 
* LED's beat Incandescent globes after 3-and-a-bit years.

To quote Mitra again:

Obviously this depends on assumptions about inflation in electricity prices, so I've added a second tab, where I assume electricity inflates at 7% more than general inflation.

HTT has changed the inflation figures for South Africans: electricity is due to go up 25% for the next 3 years (and probably beyond that too).

Don’t give up on the LED globes - in the near future, I’m sure that their prices will drop drastically and will replace CFLs.

Here are the screen shots of the charts showing the results: no inflation, and with inflation (note: horizontal axis have different scales)
image        image

Is it just me, or do you also think that the power guzzling little incandescent globes should be banned!

To see the actual formulae and data download the calculator here:  HTT_Calculator_Lighting_cost_analysis_SouthAfricaAug2011.xls

The electricity rates for Cape Town for 2011 are here:


  1. Well according to some blog I've read yesterday. Incandescent globes are now banned (in the US). All the manufacturers has already stop manufacturing and only stocks in the stores are allowed to be sold until it's all gone.

  2. Hi "Electrical Training Courses"

    Thanks for your comment, and I'm very glad to hear that - perhaps South Africa will also implement those rules very soon!

    Rgds HTT ;)


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