Dear Secret Santa


Later this month, I will be attending a Fake Xmas Day with a few friends, in which we will be participating in the years-old tradition of giving gifts to other people in a clandestine and covert fashion according to the official rules for International Secret Santa-ball.

Since one participant has already remarked upon how I deserve little but coal this Christmas, I write here a heartfelt letter to my Clandestine Claus to discuss and develop the consequences of getting me nothing but some lumps of black Carbon this Wintermas festival. If you’re up for the journey, I’d love for you to join me.



Dear Secret Santa, 

According to and their standard coal sale price of £0.24/kg (based on a rate of £240 for 1 tonne), for my Secret Santa present of up to £10 value, I can be looking forward to (at best) 41.67 kg of coal from you this Christmas. This is, of course, assuming that you spend the whole £10 allocation, and that you also purchase this in the context of another £230 worth of coal – let’s say that you don’t like me quite that much or I’ve been annoying to you recently, so let’s round that down to 40 kg of coal for my £10 gift.

According to, 1 kg of coal burns to give 8.13 kWh so with my 40 kg, I can look forward to getting 325.20 kWh of electricity for my money (or, more accurately, my Secret Santa’s money). Of course, I don’t have an coal-burning generator, but there’s teething troubles with any plan.

Given that my living room has two primary lightbulbs, each using 42 W (energy-saving equivalent of 60 W), then I can use my 40 kg sack of coal to fully illuminate my living room for 3,871 hours; or 161 full days. However, since I don’t generally need to have the lights on for at least 8 hours a day, I could afford to fully illuminate my living room for 16 hours a day for 241 days. Assuming that I don’t need to heat my flat (it’s okay, I’ve got lots of jumpers), eat anything (I guess if I get hungry, I could start eating the coal) or provide any additional entertainment or amusement (I have books and board games that don’t need any power), then my £10 sack of coal would likely keep me basking in photons until at least June, depending on solar conditions. I guess I could burn the empty sack as well when the coal runs out, to give me an extra hour or two of brightness.

Of course, the coal-burning generator will probably take up a significant amount of my living room and make it very difficult to invite guests over (the noise and heat and smoke will also not be good for dinner parties), but since I will want to be saving all the available photons for myself, it is likely that I wouldn’t be inviting friends around anyway. Given that using some of the coal to heat water would also be an extravagant waste, I likely wouldn’t be able to take any baths or showers anyway, so guests may not want to be in my company in any case. The diet of cold beans and Ryvita crackers that I would have to embark upon would also probably not help to endear myself to those around me.

How will £10-worth of of coal compare with my standard electricity tariff though, I hear you ask? Well, according to average electricity tariffs from, 1 kWh would cost me approximately 10 pence, therefore the equivalent coal price would equate to an extra 14 pence per kWh; or £1.14 more than simply using the standard National Grid input for 8.13 kWh. I suppose that this is an added expense for my Secret Santa that accurately embodies the festive spirit and goodwill to all men.

But what about wrapping? Either my gift-giver wraps the entire sack of coal (which contains the 40 kg of coal itself), or wraps each lump of coal individually. Let’s take a look at the relative expense of doing each option:

1. Wrap the Entire Sack

– For this, I am going to assume that the coal is going to be held in a 50 kg jute/hessian sack, along the lines of ( This sack is 43×23.5″, or 109x59cm. Theoretically, this would then require a minimum of 0.64 square metres of wrapping paper to wrap the sack; perhaps more if the sack bulges/stretches due to the weight of coal. For the sake of argument, let’s say that you need 0.7 square metres.

According to, one 2×0.7 m roll of wrapping paper (1.4 square metres) costs approx. £1; therefore to wrap the sack itself, you would need to use half a roll, at a cost of around 50 pence. In this calculation, I have not included the cost of sellotape and/or bows/ribbons, which I assume that everyone keeps in bulk at home and close-at-hand for any wrapping emergency.

The gift is now complete.

2. Wrap Each Lump Individually

– To investigate this, I went to my parent’s shed and looked at their stocks of coal. Taking a single lump at random, I found that it was approx. 4.5 cm in diameter (assuming roughly spherical, which is a big assumption) and weighed approx. 52 g. Extrapolating, this would mean that there are approximately 770 lumps of coal in the sack, each with a surface area of (6.36 x 10^-3) square metres, giving a total surface area of 4.9 square metres.

Using the same maths as for Option 1, this would require around 3.5 rolls of wrapping paper, costing £3.50. Naturally, I have not taken into account the wrapping time taken to embark upon this endeavour, which would of course be considerable, unless my you are able to delegate this task to your resident House-Elf. I would, of course, rate how much my you like me as a friend based upon whether you decide to wrap the sack or wrap each lump individually, and base all future gift-giving to them on this observation. The quality of wrapping will, of course, also be ruthlessly judged and scrutinised and a total score returned to you at some point in the New Year.


So, what’re the conclusions?

Well, the primary one is that – for the purpose of making use of my gift of 40 kg coal – I will be required to invest in a coal-burning electricity generator. In conducting this research, I had considerable difficulty in finding any available power plants for sale. Apparently Battersea Power Station was last sold for £400Million according to Wikipedia, but since Battersea is out of commission and would require significant refurbishment in order to make it coal-running again, I would estimate that a cost in excess of £500Million would be necessary in order for me to translate my 40 kg of coal into available electricity. Since Battersea could apparently consume over 1 Million tonnes of coal per year, this gives a hourly coal consumption rate of 114 tonnes. This would mean that it would take approximately 1.26 seconds to burn 40 kg. Therefore, your very kind gift of £10-worth of coal would take the same amount of time to be consumed by heat as it takes for light to travel from the Moon’s surface to the Earth.

Of course, you could just buy me Trent Reznor’s and Atticus Ross’ glorious soundtrack for Gone Girl instead, which would provide me with many more hours or entertainment and amusement, but I guess it’s really up to you.

Yours tediously,


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