GREENer HOUSE

This week, my favourite little Rinnai gas heater stopped working when load shedding began on a cold night. It may use gas, but it also has an electric fan so it isn’t Eskom-proof. I’ve been looking at alternatives.

Last year at about this time, I wrote an overview of home heating options. In it, I ranked an open fireplace heated by gas 8th out of 11 options, well worse than average. This is because gas may burn cleanly, but any open fireplace loses most of its heat up the flue.

I failed to mention then that I own a Jetmaster open gas fireplace. In the past, I only used it a few times a year for ambience when we had guests, but I’ll have to use it a lot more during load shedding this winter since it’s my only heater that runs without electricity. That’s a problem, because LPG has risen in price from R367 for a 48 kg bottle when I installed the Jetmaster in 2001 to R820 now. And according to my own ranking, I’ll be using one of the least environmentally friendly options around.

When I first installed the Jetmaster, I briefly considered a wood stove, but I knew that wood burning was a source of carcinogenic particulates, and I didn’t see how wood made sense in a semi-arid country with so few trees.

I’ve learned two important things since then. First, I got a quick lesson in urban forestry a few years ago when I had to remove a giant dying oak from my garden. It broke my heart to see tons of potential firewood being carted away by a tree-feller who told me he was taking it to the dump. (The trunk and limbs were too large for me to split.) The logs would ultimately decompose, releasing greenhouse gasses without benefiting anyone. I called around and learned that some other tree-fellers cut and split the wood they retrieve to sell for firewood. In the future, I would only use a tree-feller who recycled this way.

Johannesburg is sometimes called the world’s largest urban forest. I suspect that this is hyperbole that could not be proven, but the fact is that the city creates enough firewood to heat many more local homes than it currently does. (Though not all of the homes, of course.)

The second education I received was when I began researching the latest wood stoves and fireplace inserts. They aren’t just better than open fireplaces, they are unrecognizably better. An open wood fireplace loses 90 percent or more of its heat up the chimney and releases about 50 grams of particulates per hour. Anyone who has read what I have writing about diesel emissions in the Mail & Guardian and on this website knows that particulates are a serious health risk.

But modern stoves typically emit 2 to 4 grams of particulates per hour, and some are closer to 1, that’s just 2% of the particulate pollution from a wood-burning open fireplace. And about a quarter of what a typical diesel car might produce. In addition, they retain 75 percent or more of the energy in the wood to heat the room, losing just a fraction to the flue. A free-standing stove unfortunately doesn’t suit my lounge, but the fireplace inserts are only a few percentage points less efficient and just as clean.

Perhaps most important, burning wood is widely considered to be almost carbon neutral, because a decaying dead tree would release carbon dioxide anyway, while a new tree growing in the place of the old one absorbs the greenhouse gas. Firewood from the urban forest is even closer to carbon neutral than most because it was going to be cut anyway and involves minimal transport.

Only two fireplace inserts fit my opening, but they seem like good units. I’m seriously considering the Scan DSA 3-5, which rates at 76 percent efficiency. I haven’t yet found particulate emissions data for this fireplace, but it seems similar to the DSA 4 which emits a very low 1.1 grams of particulates per hour. If I could choose among a wider range of wood stoves, I would look for one with the Swan eco-label. Among the brands in South Africa, Scan, Morsø, and Jötul all have stoves that meet the wide variety of environment criteria to earn the Swan logo. A list of Swan stoves can be found here.
These advanced, closed-combustion stoves are not cheap. Expect to pay at least R10 000, and up to R40 000 for a top-of-the-line wood burning stove. But the wood is cheap. Malcolm Sims of Cosy Heating has done calculations suggesting that gas now sells for R1.23 per kilowatt hour of energy, whereas wood is about 30 cents per kwh if burned in a 75 percent efficient stove-cheaper than electricity. (Cosy Heating sells both gas and wood heaters.) Comparing my inefficient Jetmaster with the Scan fireplace, I could heat with wood for one-tenth the price, though the Jetmaster offers greater control in adjusting the flame, which would mitigate that somewhat.

Sadly, Cosy Heating says that my Scan fireplace is out of stock because of the load-shedding rush. So for the next seven weeks we’ll be huddling next to the open gas fireplace when the lights go out, and thinking about how warm that chimney must be.

A warm, green towel, served medium-well

A friend of mine stopped by yesterday on his way home from shopping for a heated towel rail. He had been fretting for years at his wife’s extravagant use of the tumble dryer simply to warm and dry a single towel before bathing. He worries that tumble dryers use vast amounts of electricity. I used to have a similar affliction, until my tumble dryer broke down last year. I simply didn’t bother to repair it, and I have been a happy man ever since.

The towel rail my friend wants to buy, he told me, uses about as much electricity as a single light bulb, or 100 watts. Though my friend is a former maths teacher, I wasn’t convinced that he had done his calculations.

Heated towel rails are designed to run constantly; they generally don’t come with timers or thermostats, other than a safety shut-off to prevent overheating. If he runs this towel rail constantly for a year it will consume 876 kilowatt hours of electricity and add nearly a ton of carbon dioxide to the atmosphere. In my house, that would mean a 10 percent jump in total consumption most months. And at the rates just proposed by the Johannesburg municipality for the coming year, the towel rail would increase his annual electricity bill more than R350. If rates triple over the next several years, as predicted by some experts, the annual cost would approach R1000.

Tumble dryers use roughly 2000 to 3000 watts. That’s terrible. But presuming that his wife doesn’t leave the tumble dryer running all day to keep her towel warm and dry, it might use less electricity than the towel rail. Run a 2500 watt tumble drier for a 30 minutes a day and it will use less than half the electricity—and contribute half the carbon dioxide—of  a round-the-clock towel rail.

That’s still not good for the environment, however. The almost-environmentally-friendly solution is to have an electrician install the towel rail with a switch and a timer and then use it a few hours a day in the winter and turn it off entirely in the summer. The hundreds of rand you will save each year will easily pay for the timer. The problem with this solution is that it contributes to load-shedding because it will add to your electricity consumption at the exact morning and evening peak hours when Eskom has no spare capacity.

If you really can’t see a way to keep your spouse happy without warm towels—and I am very conscious that sometimes we must compromise to avoid marital misery—I suggest trying the microwave oven. WARNING: YOU CAN BURN YOUR SKIN OR EVEN START A FIRE IF YOU HEAT A TOWEL IN THE MICROWAVE FOR TOO LONG. I would not even attempt this in a microwave without a digital timer, and children should not be allowed to try this unsupervised. For my 750-watt microwave oven, 30 seconds warms a small towel nicely and 45 seconds heats a large bath-sheet towel to perfection. Thirty seconds at 750 watts is a mere 2 percent of the electricity used by a 100-watt towel rail in 3 hours. If you don’t have a doting lover on hand to run the warm towel from the kitchen, warm two towels for 30 seconds each and wrap one inside the other to keep warm while you bath or shower. Just because I’m opposed to global warming doesn’t mean that I don’t support wet-body warming.

One is greener than the other

This week I took delivery of a 48 kg cylinder of liquid propane gas. This may seem odd, because I only use gas for heating in the winter. (I wrote about this here.)

But it was all part of a plan. Because burning LPG purchased in the summer may be about the only way to use a fossil fuel at virtually no cost to the environment. That’s right, no net carbon dioxide emissions, sulfur dioxide or any other nasties will be released into the atmosphere as I stay warm burning this gas in the coming winter.

The logic is this: LPG is a byproduct of the refining process. Wherever petrol is made from oil, gas or coal in South Africa, some LPG is produced. As a friend a Sasol first told me, in the summer, when LPG demand is down, these plants run out of storage capacity for LPG and frequently flare it. So if I work on the assumption that my new bottle of gas would have been flared into the atmosphere anyway, I can burn it with a clean conscience.

I planned ahead for this moment back in August, when one gas bottle was depleted. I always have one spare 48 kg cylinder on hand, and replace an empty as soon as I switch over. But two weeks into August I did some quick calculations and figured there was no way my new bottle would run out before warm weather arrived.

Of course, if South Africa had a rational, competitive market, LPG prices would come down in the summer, everyone would have a financial incentive to plan ahead and buy gas in the summer, and flaring of LPG would come to an end. But anyone who buys bread or has a bank account in this country knows that we do not have a rational, competitive market.

So should I buy more LPG bottles to get me through the winter? I don’t know. I worry that South Africa could run into a gas-cylinder shortage this winter. So many people are switching to gas for cooking because they no longer trust Eskom. I will try to investigate the gas-bottle supply situation before winter arrives. If it looks good, I will buy an extra bottle and let you know.

Any golden white elephants—or rhinos—in your house?

In recent days, the gold price is breaking record after record. Add to that the somewhat weaker rand, and your jewelry box is starting to look like, well, a gold mine.

If you decide to take some profits on a rarely worn bracelet, as I recently did, the environment will benefit even more than your bank account. In November, dozens of South African corporations released data on their greenhouse-gas emissions as part of the South African Carbon Disclosure Project. They should be commended for their effort. Knowing your emissions is a critical first step toward reducing them. Two of the companies were gold miners, and their disclosure came as a shock to me. For each ounce of gold produced by Harmony Gold Mining, 2.1 tons of carbon dioxide are released into the atmosphere. Yes, read it again, 2.1 tons of CO₂ for an ounce of gold. If you don’t believe me, see here.

AngloGold Ashanti had significantly lower figures, probably because it is less dependent on deep underground mines in South Africa, but the average of the two companies still comes out at 1.14 tons per troy ounce. This is not far off from a figure I got using data for the South African gold mining industry as a whole in the year 2000, 1.3 tons of CO₂ per troy ounce for electricity usage alone.

Using the 1.14 figure, by my calculations, I would have to drive my Honda Jazz from Johannesburg to Cape Town and back about three times to emit the carbon dioxide contained in a Krugerrand. (And I’m leaving aside the water pollution, local air pollution, and landscape scarring that gold mining causes.)

This might give you some pause when your anniversary next comes up, but it does make the current high gold price a perfect opportunity to recycle some gold and prevent further mining emissions. I found a medal that had no real sentimental value and my wife found a clunky bracelet that she hadn’t worn in more than 20 years. Yesterday, a gold and coin dealer paid me more than R4,000 for the two, thereby saving 783 kilograms of CO₂ using to the Anglo/Harmony average. It was like buying a carbon offset, except I got paid for it. I’m considering going back with a pair of silver candlesticks.

I remember that driving all the way to Bedfordview just to sell a little gold gave me a twinge of green guilt. Not anymore. I now realize I could have driven all the way to Bulawayo.

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.