GREENer HOUSE

The Mail & Guardian has now put the full, uncut version of my diesel article on their website. Click here to read it.

If you’ve read my article in today’s Mail & Guardian, you already know that diesel is not quite the panacea to South Africa’s environmental problems that the advertisers would have you believe. South African diesel fuel is still much dirtier than the diesel available elsewhere, and so are our diesel cars. So they play a large part in the smog and particulate pollution in South African cities. The last two-fifths of the article were supposed to explain why diesel vehicles are also not quite the solution to global warming that some think they are, either. But that part of the article was lopped off at the last minute before printing, for some reason. Here’s the rest of the story . . .

. . . These problems are all local, however, and some would argue that the far-reaching impact of global warming means that some diesel pollution must be tolerated. But diesel’s potential for reducing greenhouse gas emissions is regularly overstated. BMW’s X5 brochure, for example, notes that their diesel model uses “up to a quarter less fuel than its competitors,” including the equivalent petrol X5. It adds that this “of course, means a reduction in the greenhouse gases responsible for global warming.”

One little-known reason for diesel’s superior efficiency, however, is that the fuel is denser than petrol, with more carbon. As a result, litre-for-litre it gives off more earth-warming carbon dioxide when burned. So in measuring the grams of CO₂ per kilometre, Britain’s Vehicle Certification Agency finds that the X5 3.0sd diesel is only 11 percent better for the atmosphere than the petrol version, despite having 25 percent better fuel economy. Fuel consumption “is only really useful in terms of amount of money you’re going to spend on fuel,” notes Frank Schwegler, president of South Africa’s National Association for Clean Air, “but greenhouse-gas emissions is quite a big factor to consider.”

For now, finding a car’s CO₂ emissions per kilometre at a dealership requires scrutinizing the fine print of a technical specifications sheet, if the figure is there at all. Starting in mid-2008, however, all new cars in South Africa will have to display this number—as well as litres per 100 kilometres—based on standardized measurements that can be compared between brands.

In the meantime, the Union of Concerned Scientists suggests that car shoppers should adjust a diesel car’s litres-per-100-km figure upward by 18 percent. Comparing the resulting figure with the fuel economy of a petrol vehicle puts the two on an equal footing as far as greenhouse-gas emissions are concerned.

Even after those adjustments, diesel engines remain somewhat more efficient than their petrol counterparts. And with cleaner Euro 3 and Euro 4 compliant vehicles arriving now in showrooms, some environmentally conscious consumers may decide to tolerate diesel’s local pollution—or the high cost of effective emission controls—in exchange for the lower greenhouse gas emissions. As if that decision was not complicated enough, a more vexing quandary faces diesel buyers at the filling station.

Since Sasol’s coal-to-liquids plant in Secunda is the largest source of ultra-low-sulphur diesel in South Africa, opting for 50 ppm sulphur diesel over ordinary 500 ppm actually quadruples the chances that the fuel in the pump is coal-based.

Sasol’s Fischer Tropsch coal-to-liquids process is an incredibly dirty way to make an incredibly clean fuel. Every drop of diesel that the company makes from coal is so low in sulphur—approximately 10 ppm—that it could be sold in virtually any country in the world.

But the Secunda facility emits about 60 million tons of carbon dioxide into the atmosphere each year. That’s barely less than the greenhouse gas emissions for all of Israel and its 7 million people. In making a litre of coal-to-liquids diesel or petrol, Sasol sends well over three kgs of greenhouse gases into the atmosphere, far more than a car will emit while driving on that litre.

Sasol already supplies half of all the ultra-low-sulphur diesel sold in South Africa, and it is the best situated to increase supply as demand rises. Bizarrely, Sasol has to sell most of its clean diesel as regular 500 ppm sulphur diesel for a lower price; demand for 50 ppm is not yet high enough. As sales of “green” diesel cars grow, Sasol can sell that same fuel for more money as ultra-low-sulphur to take a dominant market share in the 50 ppm segment.

It will be a sad irony when most of the millions of tons of greenhouse gases spewed by Sasol to make diesel is paid for by the drivers who bought the most “environmentally friendly” cars.

Even the complete version of my article on diesel fuel leaves some open questions. Before you ask, here are my answers:

So which car should I buy?

If the answer were simple, I would have fit it into the article. The conundrum is this:

Diesel cars emit somewhat less carbon dioxide. (Not as much less as you thought, but less nonetheless.) But diesel cars emit more local pollutants. But the newest, clean, Euro 4 diesels driving on ultra-low-sulphur fuel emit acceptable levels of local pollutants. But half of all the ultra-low-sulphur diesel in South Africa is made in a way that emits huge amounts of carbon dioxide.

You can’t win.

You also can’t use diesel as an excuse to buy a bigger, more powerful vehicle than you need. That’s exactly what the car companies are trying to get you to do. (See question below: “Why are SUVs cleanest?”) I think that most city dwellers, especially those on the Highveld, should buy the most fuel-efficient petrol car they can find that suits their needs. If you can afford it, the Toyota Prius is ultra-clean for both local pollutants and greenhouse gases.

If you live in a rural area in the Highveld, where local air pollution from traffic is not as much of an issue, you might consider buying a diesel vehicle and running it on normal, 500 ppm sulphur diesel. You are most likely to avoid coal-based fuel that way and will reduce your contribution to global warming. (Note that if your manufacturer says you must use ultra-low-sulphur fuel, it could damage your vehicle to use 500 ppm sulphur diesel.)

If you live in KwaZulu-Natal, most of your fuel comes from petroleum. With the coal issue set aside, diesel makes more sense. Look for the vehicle—petrol or diesel—with the lowest CO2 emissions that suits your needs. In KZN cities, you should only buy a diesel if it meets Euro 3 or Euro 4 specifications and fill it with ultra-low-sulphur diesel.

Cape Town is even more complicated. Fuel retailers generally buy from the nearest refinery, but Sasol transports ultra-low-sulphur diesel all the way from Secunda to its filling stations in Cape Town. I wouldn’t buy it. BP stations get their ultra-low-sulphur diesel from the Durban refinery that BP owns with Shell. I don’t know about the others.

Does a diesel make economic sense?

The Diesel Dilemma, a report by the Union of Concerned Scientists, concludes that:

Gasoline vehicles are more cost-effective than diesel for reducing oil use and lowering global warming pollution.

By that, they mean that if the extra expense it takes to make a clean diesel engine were put toward greater efficiency in petrol vehicles, the petrol vehicles would save more oil and greenhouse gases than diesel cars. Unfortunately, other than hybrids like the Prius, few petrol cars have benefited from that kind of attention toward fuel economy.

Looking at clean diesels available in South Africa, the BMW X5 sd costs an astounding R68,000 more than its petrol equivalent the X5 si. Even after 150,000 kms, you would be R47,000 poorer, at October’s fuel prices. The diesel Honda CRV, which has perhaps the most advanced diesel engine on earth, emits 10 percent less carbon dioxide than a similar petrol CRV and costs R20,000 more. After 150,000 kms, you would be only halfway toward recouping that differential.

I’m not a great believer that every expenditure for the sake of the environment must pay for itself. If someone in Durban really needs a 4×4 soft-roader and is willing to pay the extra money for the sake of the earth, they should buy a diesel CRV. I’m just not sure how many people out there really need a 4×4 soft-roader.

Smaller diesel cars may have a smaller price differential, but few if any small diesels in South Africa today are clean enough to meet Euro 4 emissions standards. In 2008, some will be available, and perhaps they will pay for themselves over time. They certainly will make more sense for the environment than a 3-litre diesel powerhouse with a lot of emissions controls on it.

Why are diesel SUVs cleanest?

The cleanest diesel engine BMW has brought to South Africa is in its giant X5. Honda’s cleanest diesel is on the 4×4 CRV. VW’s only Euro 4 vehicle in South Africa so far is the Touareg SUV. Volvo has put its best diesel emissions controls on the 4×4 XC. What’s going on here?

I put this question to Jan Lotter, the product planning manager for BMW South Africa. He laughed, and said that I had made a good observation. Then he said:

There’s a growing awareness of SUV consumption; people are talking about carbon footprints, environmental impact. This is a little more of an investment to make them more acceptable.

I think he’s right. It’s a last-ditch effort to keep people who are starting to feel that it’s environmentally unacceptable to drive a 4×4 to Sandton City from buying a smaller, less expensive car.

Lotter made another salient comment:

The unfortunate thing about diesel is that it is still expensive. With the invention of common rail diesel technology, and going to higher and higher pressures [to make diesel engines cleaner] it becomes difficult to introduce entry-level diesels.

BMW has a small, Euro 4 diesel car that can even beat Toyota’s Prius in fuel efficiency, the 118d. But it isn’t sold in South Africa.

Does it really make a difference whether I buy coal-based fuel?

One could argue that avoiding coal-based ultra-low-sulphur diesel from Sasol’s Secunda plant does nothing for the environment. Fuel is in short supply in this country and Sasol will keep producing to capacity. The company may end up selling the fuel as regular diesel and it may end up selling the diesel somewhere else, but Secunda’s emissions are not going to decline just because fewer people buy ultra-low-sulphur diesel in the interior.

This argument has some validity, but I would make three counter-arguments:

1. Sasol makes more profit selling their diesel as ultra-low-sulphur diesel. The more profit they make on diesel, the more likely they are to go ahead with the second coal-to-liquids plant, which is now in the feasibility-study stage. Such a plant would be a disaster for South Africa’s greenhouse gas emissions.
2. If ultra-low-sulphur diesel becomes in short supply, the government may be more favourably inclined toward another coal-to-liquids plant.
3. It might just bother your conscience to think that the source of all those greenhouse gas emissions killing polar bears and ruining the crops of African farmers is sloshing around in your fuel tank.

Don’t you have anything nice to say about Sasol?

Sasol does an impressive job of reporting emissions data and was willing to let some of its experts talk to me openly for this story. The refinery owned by BP and Shell, by contrast, would only answer questions by email and mostly didn’t answer questions at all. Sasol’s greenhouse gas emissions are edging down relative to their total production, partly because they are using more gas from Mozambique, which is less polluting than coal. There, I managed to say something nice about Sasol. (But if you haven’t read the M&G article yet, their Secunda plant has roughly the same greenhouse-gas emissions as Israel.)

Don’t you have anything nice to say about BMW?

I’m afraid that BMW’s marketers set themselves up for criticism by portraying a big SUV as a solution to global warming. That said, the company is working on some very interesting technologies for improving the fuel consumption of both petrol and diesel vehicles. In 2008 we may see the first BMWs that cut the engine instead of idling at a stop light and use the energy from braking to recharge the battery.

Three aging appliances in my kitchen have been declared beyond repair, which has led me to undertake a lot of research on appliances. A good starting point I have found is Which?, the British non-profit magazine and website that thoroughly tests and reviews consumer products. I will report on my research on dishwashers, etc., when I have completed it. In the meantime, I stumbled upon this page in on the Which? website that has interesting, straightforward, and surprising information on television electricity consumption.

I had always assumed that LCD televisions use far less power than standard CRT (Cathode Ray Tube) televisions, since this is the case with computer monitors, as I reported here in my post on saving electricity in the office.

Which?, however reports that after testing dozens of TVs, it found that a 32-inch CRT TVs use 50-100 watts, similar sized LCDs use 100-200 watts, and 42-inch Plasma TVs (they aren’t made in the 32-inch size) consume 200-300 watts. That’s up to 6 times more than a CRT only 10 inches smaller.

Though I believe the Which? does very thorough and unbiased research, I do think that the full story is slightly more complicated. A revealing chart produced by the Australian government when researching electricity consumption by TVs shows that in the smaller sizes (below 40 cm) , LCD TVs are more efficient on average. This would explain why they are the greener choice for a PC monitor. But CRT TVs don’t experience as great a leap in consumption as they get larger. LCD and Plasma TVs use a lot more electricity with each step up in size. Beyond 60 cm, most CRTs are somewhat more economical, though there is enough variation between models that it is possible to find a large LCD that outperforms a same-size CRT at the plug.

As for Plasma TVs, they are simply energy hogs. The larger ones can draw 500 watts or more. Some guides to televisions will divide the consumption by the size of the TV, which makes plasma televisions look a little better. But I think this is beside the point. One of the most important decisions a television buyer must make is the size, and it is important to know that making do with a smaller television is much better for the environment. If you already own a plasma TV, you can reduce its power usage by turning down the brightness. (Dim the room lights at the same time and you’ll save again.)

And, as I explained in this post, when you’re finished watching, take the consumption all the way down to zero. Don’t put it into standby with the remote; turn it off at the television itself.

I spent the morning meeting with the creator of South Africa’s first Internet carbon-footprint calculator, which will premiere on Greener House in the near future. He is a brilliant young engineer who has just been named the best Certified Energy Manager in South Africa for the year, so you can trust that the calculator will be backed by solid data. Measuring the amount of greenhouse gases produced by a person is a tricky and inherently imprecise task. But he is committed to making the calculator as accurate and as useful as possible.

There are plenty of carbon calculators in the Internet, so why do we need another one? Because the others make assumptions that you live in America, the U.K., or somewhere else that has conditions different to South Africa’s. For instance, if you use a calculator from a country that uses a lot of nuclear power for electricity, the carbon contribution from your electricity consumption will be misleadingly low. And no other country produces significant quantities of petrol and diesel from coal; our calculator will take that into account as well.

We will be glad to consider refinements to the calculator once it is up on Greener House. But we don’t want to just throw up a rough draft, hence the long meeting today. Our aim is to have it up and running by the end of the year. It’s tough, I know, but try to be patient.

Winter is a tough time to hold down electricity consumption. Days are shorter so lights burn longer. The cold air begs for hot tea, hot meals, hot water, and hot electric heaters. (See this post on heaters.) Even solar-heated water needs an electric boost in the winter. But there is one easy place to save electricity as the days get colder: the swimming pool.

One of the best things anyone can do to make a greener house is to fill in the pool. Swimming pools waste water, use huge amounts of electricity, and require toxic chemicals. But my kids would kill me if I filled in the pool, and there are ways to mitigate the environmental cost of a pool.

The first priority is to get a pool cover that keeps out dirt and ultraviolet and prevents evaporation. If it’s a bubble cover, it will keep your pool warmer, too. In Namibia the law insists on pool covers to prevent evaporation. A cover will save thousands of litres a year.

Ultraviolet breaks down chlorine, which is why you have to add cyanuric acid to stabilize the chlorine. Put on a pool cover and you can save on both stabilizer and chlorine. Most important, with less dirt and more effective chlorine, you should be able to reduce your pool pump’s running time.

In most homes with a pool, the pump is the second or third largest consumer of electricity, after the geyser. If I followed HTH’s standard recommendation to run my pool pump 12 hours a day in the summer, and if I hadn’t resisted a sales pitch a couple of years ago to trade in my 750 watt pump for a new 1 100 watt model, I would be using 13 kilowatt hours a day to filter pool water, more than half my current total daily consumption.

Ignore HTH’s 12-hour guideline, and rather follow the suggestions of the California Swimming Pool Industry Energy Conservation Task Force:

Reduce filter operating times to no less than 4 to 5 hours per day during the summer and 2 to 3 hours per day during the winter period. This will reduce annual electrical consumption by 40 to 50 percent. Normal and heavier swimming use may require as much as eight or more hours filtration per day. Should water clarity or chemical imbalance indicate inadequate filtration, immediately operate the filter until acceptable water clarity has again been established. If additional filtration is still indicated, increase filter operating time in one-half hour increments until the water remains clear and properly balanced chemically.

I run my pool six or seven hours a day during the summer. Since cold water inhibits the growth of nasties, yesterday I reset the pump timer to three hours for the winter. Eskom struggles to keep up with peak winter demand in the morning between 6 and 10 a.m. and in the early evenings between 6 and 9 p.m., so make sure the timer is not set to run the pump during those hours.

All of this inspired me to do some calculations. A cubic metre of coal can produce roughly 3 000 kWh of electricity. My pool holds roughly 30 cubic metres. So if I kept a 1.1 kw pump running 12 hours a day year-round, as many South Africans do, the coal burned over 18 years to keep that pump going could fill the pool to the brim. Better a green pool than a black one.

My Rinnai

I saw frost for the first time in 2007 today. My wife has started to grumble about the cold. And the stores are full of heaters for sale, all of them claiming to be energy efficient. It’s time to review which heating options will warm your home without heating up the planet too much.

First, the worst: electric underfloor heating and open fireplaces. Talk to any underfloor heating salesperson, and they will tell you that underfloor heating is incredibly efficient. Talk to any homeowner who has had it installed, and they will tell you that their toes are very warm on the tiles (don’t these people own slippers?) and that their electricity bill shot up the day they turned on the underfloor heating.

The issue is not so much whether underfloor heating is efficient or not. It’s a form of central heating, and most South African suburban houses are not built for central heating. They have big, draughty, single-glazed windows, and uninsulated walls and ceilings. When I moved into my house, each room had a brick with big holes in it to let in outside air, for heaven’s sake. To centrally heat such a house with coal-derived electricity is an environmental abomination.

Open fireplaces have lots of charm, but two big drawbacks. The first is that most of their heat goes up the chimney, and in doing so, draws cold air into the house through any leaky door or window it can find. Nature abhors a vacuum. The second drawback is that, whether burning wood or coal, they emit lots of pollution up the chimney.

According to The Consumer’s Guide to Effective Environmental Choices, by Michael Brower and Warren Leon:

On a per-household basis, the most polluting option is wood heat. The main reason is the very high emissions of particulate matter from uncontrolled fireplaces and wood stoves. Particulates are given a heavy weight in our air pollution index because of strong evidence that they cause serious health problems.

I hate to diss wood heat, because it is carbon neutral, presuming that a new tree is growing in the place of the one you are burning. A good compromise is a modern, super-efficient wood stove, such as the ones sold by Franco-Belge or Morso. The best wood stoves produce one-twelfth the emissions of a typical fireplace.

Electric heat in all forms is relatively efficient, but that isn’t a great help because generating the electricity from coal is very inefficient, and releases far too much pollution and carbon dioxide. If you are heating a relatively small space for a couple of hours in the morning and few hours in the evening, however, it is an affordable, environmentally tolerable option.

Research at the University of Pretoria found that the quickest, most efficient electric heater for warming a space is a fan-assisted heater with a thermostat. Fin radiator heaters—often called oil heaters because of the liquid circulating inside them—and other heaters without fans are slower to heat a room and let much of that heat drift to the ceiling.

Radiant bar heaters, which glow red, do not heat a space, but can efficiently heat any person who stays close to them. If you are staying put, reading or working, they may be your best option, particularly if you buy one with a low wattage setting. (1000 W or less) Leaving one of these heaters on when no one is in the room, however, is a complete waste. An electric blanket is another good option for anyone who isn’t moving.

If you are lucky enough to live in a Johannesburg suburb with piped gas, this is an excellent option, particularly now that South Africa is importing natural gas from Mozambique. Gas is the cleanest-burning fossil fuel and releases the least carbon dioxide, too. Bottled propane gas also burns cleanly, but its global-warming credentials are tainted by the fact that in South Africa much of it is produced from coal. Gas is also more efficient than coal-derived electricity because the heat from burning the gas goes straight into your house, bypassing the inefficiencies of generating electricity.

Burning gas in an open fireplace takes us right back to where we started, however, with heat escaping out of the chimney. My favourite gas heaters are the pricey, but super efficient ones made by Rinnai. My Rinnai has given me three years of faultless service. I keep large, 48 kg bottles of LPG outside my house, piped to a wall outlet where I connect the Rinnai. It produces heat in seconds and uses very little gas. (To find a local dealer, phone the distributor Jay MacDonald and Sons, 021 696 7930.) The only problem is that my children fight over who gets to sit closest to it when they turn it on in the mornings.

I’ll take a risk and produce an unscientific ranking of heaters from best to worst:

1. Gas heater with piped natural gas
2. Gas heater with LPG
3. Modern, efficient stove burning wood
4. Modern, efficient stove burning anthracite
5. Electric bar heater for warming people who are staying in one place
6. Electric fan heater with thermostat
7. Other Electric heaters
8. Gas fireplace
9. Wood fireplace
10. Anthracite fireplace
11. Electric underfloor

My wife called yesterday to say that she was at a shop, confronting a dilemma. She had to choose between a 2100 watt iron and a 1400 watt model. The salesperson told her that the 2100 watt iron was better because it was much more powerful.

I don’t like to make such decisions without thorough research, but I knew that our old iron was ruining clothes and needed to be replaced soon. So I gave her an answer so obviously in keeping with my reputation that she could have saved herself the call: “Buy the one that uses less electricity.”

Still, I worried that in my constant insistence on saving energy I had saddled my household with an underpowered iron that would need hours of extra labour to press out the wrinkles in our laundry. Ha! I checked the base of our current iron. This is an appliance so beloved of my housekeeper that she resisted its replacement even though was damaging clothes. The label read 1100 watts.

This is a constant theme of modern life. The mantra that more powerful must be better has soaked into every purchasing decision, from vacuums to vehicles. One of my best decisions in recent years was to ignore a salesperson’s advice to trade up from a 750 watt pump to a 1100 watt pump for my pool. Thousands of South Africans drive cars capable of driving 200 kilometres per hour on the German autobahns, even as a growing army of camera traps ensures that all of that extra horsepower is wasted. Philips, which made both of my irons, sells 11 models of steam irons in South Africa today, and every one of them boasts a higher wattage than my old iron.

My advice when confronted with the option to trade-up in power is simple. Resist. If the old iron worked just fine, did it really need to be using 90 percent more electricity? Clearly not. Our new 1400 watt iron works so beautifully that my housekeeper has forgotten she ever wanted to keep the old one.

I finally took my family to see “An Inconvenient Truth,” yesterday. This global-warming documentary has lasted for three months now at Cinema Nouveau, Rosebank, which suggests that the word-of-mouth has been positive. We were an unusually tough audience: I’ve already read hundreds of articles on global warming, while my children (ages 9-15) are accustomed to more entertaining fare. So I am happy to report that we tough critics give the film two thumbs up. (To read what other critics said, see this post.)
I was nervous taking my children to such a serious film. But as we walked out of the theatre, my son said, “that was a good movie, not the best movie I could have chosen, but a good movie.” I consider that high praise coming from an 11-year-old boy who has just sat through a serious, 95 minute documentary created for adults. When I stood up from my seat during the credits, my kids wouldn’t budge. They were watching the hints for reducing your personal contribution to global warming, which were interspersed among the production credits. “You already do all of those things, Dad,” said my eldest. I have a feeling that, at the very least, the film has helped them understand why their kooky father rides his bike to the post office and climbs up a ladder to clean his solar panels.

From my perspective, I found the film’s use of graphics enlightening. (And frightening.) I learned a thing or two, and the explanations of complex science were well thought out and organised. I thought that the movie successfully held the audience’s attention with a variety of perspectives, the human interest element of Al Gore’s life, and a sprinkling of humour.

My severest criticism would be that it seems very American. The brief asides about Al Gore’s political career may or may not interest South Africans. More worrisome is that in highlighting America’s role in global warming, An Inconvenient Truth inadvertently gives South Africans an opening to think, “we’re not the problem.” One graphic shows Africa’s tiny per-capita contribution to carbon dioxide production, next to America’s giant contribution. Since it was the only mention of Africa, it caught the attention of both my wife and my children. I explained to them that the millions of Africans who by necessity get around on bikes, buses, trains, mini-bus taxis and their own two feet take the credit for that low figure. If all Africans lived like the few South Africans who can afford R40 to see a movie, we would probably rival the Americans.

Eventually, An Inconvenient Truth will reach video stores and television screens. But I don’t suggest that you wait. Even an action-packed adventure film struggles to hold a viewer’s focus when competing with ringing phones and doorbells. This film deserves your full attention.

My family is away this week, so I’ve been playing with vampires. It’s not as kinky as it sounds. “Vampires” is the nickname for all of the nasty little electrical devices that suck juice from your electrical outlets even when they are supposedly off. The most common vampires are televisions and computer equipment in standby mode and battery chargers that are left plugged in even when they are idle.

I wanted to know how much these little suckers use in my house. Does their electrical consumption add up to something significant? The municipal electric meter was my measuring device. With no one else in the house to surreptitiously turn on a light, I could control exactly what was and was not drawing power.

First, to establish a baseline, I switched off all lights and geysers, and I unplugged everything, including the refrigerator. Over two hours, I used just under 0.2 kilowatt hours of electricity. I assume that means my security system draws a little bit less than 100 watts.

Then I plugged in every cellphone charger, battery charger and toothbrush charger I could find. I turned on two televisions at the switch and then zapped them “off” with their remotes, and I did the same with any video devices attached to them. I powered up the stereo amp and CD player. I plugged in my electric piano, but left it off. I booted up computers-then put them into standby mode-and I plugged in any printers or other peripheral attached to them. Finally, I plugged in two voltage converters that I use for a few appliances I brought over from America.

I want to emphasize that I was not using any of these devices. I wasn’t watching TV, listening to music or using a computer. None of the chargers had anything to charge. Nothing was plugged into the voltage converters. The lights stayed off and the fridge remained unplugged. The house was as dark and silent as you might expect it late at night when we are all asleep.

Two hours later, my municipal meter told me that I had used 0.5 kilowatt hours, which means that those thirsty little vampires were cumulatively lapping up 150 watts to do absolutely nothing. Left alone, that’s 3.6 kWh a day or 108 kWh a month, costing nearly R34 at Johannesburg’s electricity tariff. Over a year, I could be using 1 314 kWh, pumping well over a ton of carbon dioxide into the atmosphere and paying R410 for the privilege. It’s like having a leaky faucet that drips around the clock, but it’s leaking electricity instead of water.

Was my scenario extreme? Perhaps a little. Most people don’t have voltage converters. But otherwise our family lives like many suburban South Africans. Studies quoted by the Economist magazine in an article last year found that vampires account for 7 percent of domestic electricity consumption in France and up to 10 percent in some American homes. Vampires in the U.S. alone drink up the equivalent output of 18 typical power stations, according to the Economist.

I am sure that my family does not use all of those 150 watts as we sleep. My children know that remotes are for changing channels, not for switching televisions on and off; that’s the function of the button on the front of the TV. I turn my PC all the way off when finished using it, reaching behind the case to the switch at the back. And I only plug in chargers when they have a job to do. But this exercise did make me realize that there were gaps in my vigilance. I noticed that even when my electric piano was off, its AC/DC transformer at the wall was very warm, a sure sign that it was wasting power. From today, I have decided to switch the piano off at the wall when I’m not playing it. I will sleep better knowing that I have slain another vampire.