GREENer HOUSE

I didn’t even have to climb a ladder

If you’re tired of Eskom taking your money, I have good news. The national electricity company want to give you a gift worth at least R10 0000.

The gift is in the form of LED downlights, and these freebies are already lighting up my house—and saving electricity. If you have halogen downlights in your ceiling, or tracklights that use the small halogen reflectors, and if you live in Johannesburg, Pretoria, Cape Town, Durban or Port Elizabeth, this present is for you.

Until this week, when I wrote about the program for the Mail and Guardian, Eskom’s Residential Mass Rollout was actually a well-kept secret, marketed quietly to avoid long waiting lists. That is changing rapidly, however, so if you want these bulbs in a hurry, I suggest you sign up right away. Tell your friends about it only after you’re already in the queue.

For this year, Karebo is the only service provider, and will keep installing until they run out of approximately 1.7 million LEDs. From next year, Eskom promises to expand the rollout and enlist more installers as partners.

If you are interested, here are the steps:

1. Count how many downlight bulbs you can use. The maximum number you can get for free is forty. Note separately how many of those bulbs are on dimmers.

2. Consider whether you would also like free CFL bulbs, low-flow shower heads, a pool timer or geyser timer. (More about those below.)

3. Go to www.karebo.co.za and click on “sign up” in the box that should pop up in the upper-left corner of the screen

4. Fill in your details.

5. Make a deposit if you are paying extra for dimmable bulbs. (More on that below.)

6. Wait a week or two to be contacted for an installation appointment.

And here’s what you will get:

LEDs: These are top-of-the-line, warm-white, Philips bulbs rated at the same light output as 50 watt halogen downlights. They would retail for R250 to R300—if you could find them. The LEDs come in four flavours. The mains voltage, non-dimmable bulb has the lowest consumption, just 5.5 watts. That’s barely 10 percent of the 50 watt bulb it replaces. It also has the longest lifetime: 40,000 hours. They carry a three-year warranty, but I’ll consider myself lucky if I outlive these bulbs. The mains voltage, dimmable bulb is the same, except that it uses 6 watts and costs R25 extra. (For a bulb worth more than R250, it’s a steal.)

The low-voltage, non-dimmable bulb uses 7 watts, and is rated for 30,000 hours. The dimmable low voltage LED uses 10 watts. In addition, the low-voltage transformer draws some power, again proving that low-voltage is not the same as low wattage. The low-voltage LEDs not only draw slightly more power and have shorter lifespans, but they also bear the risk that a small number of transformers are incompatible with them.

Three years ago, Greenerhouse predicted that the best way to prepare for the LED revolution was to only install mains-voltage downlights. Unfortunately, I put the lights in my ceiling before I knew that. So to get the very best free LEDs, I ripped out my transformers in advance of the installers’ arrival and rewired the fixtures using R30 kits that I bought from Lighting Warehouse. (Radiant brand, models HG10 or HG11) But I’m hard-core, deep-green. If you have low-voltage lights and don’t want to fuss, get the low-voltage LEDs. I didn’t succeed in removing two of my transformers, and the two low-voltage LEDs I installed work perfectly.

Dimmers can also raise compatibility issues. Of the three dimmers in my house, two—Clipsal 2000 series—are working flawlessly with the new LEDs. One is not. At various points in the rotation, the lights will flicker and even go out. For now, I’ve learned how to position the dial so that the lights work as they should, but Karebo offers a R250 dimmer for the LEDs, and I plan to purchase one.

One final limitation: Eskom only wants working, 50 watts halogen globes. For years I have paid extra for the most efficient halogens, 20 and 35 watt IRC, energy-saving bulbs. Even if I had kept all of my old low-voltage sockets, I would have had to buy 40 new bulbs, just have to have Eskom destroy them. Buying new bulbs for no purpose other than to have them crushed felt like the most wasteful thing I’ve done all year. But in the end it has saved a lot of electricity.

CFLs: Eskom has been offering free CFLs for years, but if you missed the opportunity last time, these globes will cut your electricity consumption in fixtures that use ordinary screw or bayonet bulbs. Karebo will install a maximum of twenty.

Shower heads: I already have a low-flow shower head that I love , so I didn’t accept this gift. Karebo claims that this shower head is used in some five-star hotels. I have spoken to one homeowner who years ago removed low-flow shower roses from his home because during his showers he had to “run around chasing drips of water.” This same fussy person is very happy with the low-flow heads Karebo recently installed for him. Karebo does admit, however, that a few customers have asked for their old shower heads back. As with the lights, the installers have to keep the originals to prove to Eskom that they did their job, but, amazingly, they keep track of each shower head for a period of time in case customers want Karebo to reinstall them.

Geyser Timer: Again, I’m happy with my Geyserwise, so I said “no, thank you.” Eskom may soon insist on installing geyser timers for those who want free LEDs and do not already have their own geyser timer or solar hot water system. The timers are installed on your DB board and have four pre-programmed settings, all of which keep the geyser off during Eskom’s peak times: 6 to 8 in the mornings and evenings. This is definitely good for the country and good for Eskom. It plays a part in reducing the risk of load shedding. But is it also good for your electricity bill? Well, if you only use hot water at limited times of the day, a timer could save some electricity by keeping the geyser off while you are at work. And if Eskom carries through with its promise to charge varying rates according to the time of day, the timer could one day save you significantly more.

Pool timer: The intention here again is to keep your pump off during peak hours. Otherwise, it has only a few advantages over ordinary timers. It knows to reset the time after a power outage, for example. Karebo’s managing director says that the main opportunity for savings is that the installers will calculate for you the optimum running time for your pool and pump size. Since most people run their pumps for too long, these savings could be significant.

And the end result? Nearly every room in my house is filled with warm, beautiful, bright light. No one in my family has made a single complaint about the quality of the light. And I still marvel at the fact that my TV room is lit up by a mere 11 watts and one rather large bathroom by 27 watts. My electricity consumption, which I check almost daily, has been 12 kilowatt hours or less for 11 of the last 20 days, something that has never happened before. I would estimate that my savings now in the summer are at least 3 kilowatt hours a day, which should cut my monthly utility bill by at least R100. The savings will be much greater in the dark of winter. And the cost-benefit analysis has never been simpler: all benefit, no cost.

Giving the green light to variable-speed pumps

For more than a decade, I’ve been gradually improving the efficiency of my appliances and driving down my electricity consumption. One device had defied me, however. As hard as I looked, there did not seem to be a greener alternative to my 750 watt pool pump. Until now.

For the past 12 months, I have been testing the Viron P300 variable-speed pool pump, courtesy of the South African distributor, Fluidra . What makes this pump different is that it operates on a DC motor, so it can run at different speeds as needed. At the slowest setting, Eco, my Watts Up meter tells me the pump is using a mere 175 watts, less than a quarter of the consumption of the old pump. (A sixth, compared to the widely used 1.1 kw pumps.)

But does it work? The principle of a variable speed pump is that because a slower water flow is much more efficient, longer hours at lower speeds are the most economical way to pump enough water through the filter each day. But I have not significantly increased hours. For my 31,000 litre pool, I leave the Viron P300 on the Eco setting 8 hours a day, spring, summer and fall. And my pool stays clean. (As I have written here before, I radically cut back on pumping hours in the winter.)

The flow on the Eco setting is somewhat weaker than that of the old pump, but my Zodiac Genius still climbs the walls as long as the weir basket is clear. I think the slightly lower flow does make it more sensitive to a leaf-clogged weir, so I check it more often now. I am told that the Gemini and Kreepy Krauley pool cleaners might work even better with the lower flow because they use a hammer action, rather than a diaphram. I have not tested them on on this pump, however.

The Eco setting is not strong enough for backwashing, but that is the joy of a variable-speed pump. Just push a button and the Clean setting sends a surge of water through the filter. My measurements indicate the Clean setting uses 505 watts, still significantly less than a 0.75 kw or 1.1 kw AC pump, and with a stronger flow than a 0.75 kw can create. Beyond Eco and Clean is the Turbo setting, more suited to a fire engine than to anything I need to do with my pool.

I calculate that I am saving 4.6 kilowatt hours every day and R150 each month with the Viron P300. For someone like me who was sitting on a daily consumption just a little above Johannesburg’s magic cutoff point of 16 kWh a day, the savings could be much greater. The municipality offers a Lifeline Tariff as well as affordable rates for prepaid meters for those who keep their average consumption below 500 kWh hours a month, or 16 kwh a day. Qualifying for the lifeline tariff could save me about R3000 a year.

These savings come at a cost, however. A new Viron P300, manufactured in Spain with an Australian motor, sells for about R8300. By comparison, an ordinary AC pump from Speck costs about R2200 for the 0.75kw version. Leaving aside the Lifeline Tariff, it would take a few years of savings on utility bills to cover the difference, but there is no doubt that it is a good long-term investment. With a larger pool requiring more hours of cleaning per day, the DC pump would pay for itself more quickly.

Unfortunately, I did encounter one unexpected cost replacing my dead AC pump with a more environmentally friendly version. The Viron pump is larger, a few centimetres too large to fit in my existing pump box. A larger enclosure set me back R1800. If your box has little room to spare, check the measurements of any pump you might buy.

The Viron P300 is not the only variable-speed pump available now in South Africa. The IntelliFlo by Pentair costs more than double the price of the Viron P300, but has an extremely sophisticated controller. The pump can be programmed to run at different speeds at different times of the day. I have spoken to pool owners who splurged on the IntelliFlo pump and they were completely satisfied. Zodiac has also introduced the variable-speed FloPro ePump, which is worth investigating.

All of these pumps are astoundingly quiet compared to ordinary pumps. Standing at the far side of my pool from the pump box, I can only be certain the pump is operating if I can see the hose is pulsating.

I would love to say that I am finally at ease with the energy consumption that goes into my pool, but alas, I am a perfectionist. The ideal solution is so obvious, and yet no one offers it. A major expense of solar photovoltaic systems is the batteries that store the power for evenings and cloudy days and the inverter that converts the DC power produced by solar cells and batteries into household AC current. My pool pump has a converter to change AC current into DC for the motor. DC-AC, AC-DC—let’s call the whole thing off. Why shouldn’t solar panels send DC power directly to the pump’s motor, eliminating costly and troublesome components? (And getting Eskom out of my pool entirely.) It won’t worry me that the pump operates fewer hours under the winter’s low sun; that makes perfect sense. And if the pump slows down on cloudy days and stops at night, that’s fine too.

I’m not resting by the pool yet.

I’ve just finished reading a book called the Art of Fielding, by Chad Harbach. This wonderful novel has everything to do with baseball and absolutely nothing to do with environmental issues, except for one page or so, which includes a gem of a quote. I’ll set aside the fact that the character who says it, Owen Dunne, is probably being facetious; it’s still worth pondering:

If there’s any kind of exclusionary, private-club-style afterlife, St. Peter won’t be asking questions at the gate. You’ll just be lugging all the coal and oil you’ve burnt in your life, that’s been burnt on your behalf, and if it fits through the gate you’re in. And the gate’s not big. It’s like eye-of-a-needle-sized.

The scene above, which I photographed in my kitchen this week, is the beginning of a revolution in the way I light my house. My entire kitchen is now illuminated with LEDs, using less than 30 watts to light the entire, 5m x 5m space.

Two turning points set me in this direction. The first was a leaky roof, which blew out the transformers on one of the low-voltage halogen fixtures mounted to the ceiling. This gave me a good opportunity to start from scratch with a 220v, GU10 fixture, since LEDs, unlike halogens lamps, are better suited to ordinary, mains voltage. (Remember: Low voltage does not equal low wattage.) At Lighting Warehouse, I found a three-bulb ceiling light with a design perfectly suited to LED globes, since the radiating fins that cool the bulb are exposed to the air, as you can see above. I paid R360 each for two of these fixtures.

The second turning point was the downward slide in LED prices. I thought I had found a good deal in May, when some Makro stores were offering both Philips and Osram LED downlighter globes to replace 35 watt halogens for R295. Then I found the Osram LED at Lighting Warehouse for R250. Now that same bulb at Lighting Warehouse has dropped to just R200!

If R200 doesn’t sound to you like a bargain price for a light bulb, let me take you through the math. The Osram Parathom PAR16 35 bulbs you see pictured above use 5 watts to produce the light of an ordinary 35 watt halogen. (Actually, my Watts Up meter says they use just 4.8 watts.) If the light is on 5 hours a day at R1 a kilowatt hour—we’ll all be paying more than that by next year—it will save R55 every year on electricity alone. But the savings are greater than that because LEDs last just about forever. Philips puts a 3 year warranty on its LEDs and Osram offers a 5 year warranty. But the bulbs are rated to last many years longer. Over the course of two years, you would expect to replace a R40 halogen once, and the cost of two halogen bulbs plus the excess electricity they use is R190, about equal to the price of the LED. After two years, the LED actually pays dividends.

I chose the kitchen in part because it’s the most-used room in the house. But at R200 for LEDs, I will also consider replacing halogens in rooms that are used less constantly. The R200 Osram LED is not meant for dimmer switches, so for now I will avoid rooms with dimmers. The Philips Master LED bulb at Makro is dimmable, but I have not seen it for less than R295. By my calculations, even if the lights are on just 3 hours a day, the R200 LEDs will pay for themselves in three and a half years. (These simple calculations do not take into account the time value of money, the interest you could have earned if you had saved your R200 instead of investing it in green technology. As I’ve said before, you wouldn’t charge Mother Earth interest, would you?)

The quality of the LED lighting in my kitchen should give no one pause. LEDs have a reputation for projecting a very narrow beam. That is somewhat true for these Osram bulbs, but since they were replacing halogen bulbs that already had beams of 36 or 38 degrees, these 35 degree lights do not have a noticeably greater spotlight effect. I do think that eight bulbs would illuminate the corners of the kitchen a little better than six, but I felt that way about the halogens as well. My Osram LEDs are listed as “warm white,” and their colour is good, just slightly cooler than a halogen, but still warm. Most LEDs have a Colour Rendering Index of about 80 out of 100, which is considered very good, but not perfect. I would not choose them for an artist’s studio, but I don’t think anyone would notice the difference even as they walk between my halogen-lit entrance hall and into the light of the kitchen LEDs.

I have not yet seen LED replacements for 50 watt halogens in the stores; they will be here soon. One day we will have affordable, ultra-efficient LED bulbs to suit every fixture. But my kitchen is proof that there is no reason to wait for that day to get a head-start on a greener future.

Not such a bright idea

What grown man would get excited to see a light bulb selling for less than R100? Me, if the lamp in question uses ultra-efficient light emitting diodes. LEDs are the future of lighting, with low power consumption and incredibly long lifetimes, but their high prices have kept consumers away.  So when I noticed a R94 rand Eurolux LED at my local Builders Express, I took a closer look and took notes. The last LED globe I had seen that was meant to replace a halogen downlight had a R372 price tag on it. Was this too good to be true?

Yes, of course it was. The packaging of the Eurolux LED is inexcusably devoid of technical information, except to say that it delivers 50 lumens, a rather useless piece of information for the average consumer. It turns out that 50 lumens is an equally useless amount of light, unless you are just looking for a decorative accent to highlight your teacup collection. A 50W halogen, the most common size of downlight, delivers about 10 times that much light.

Eurolux, a company from the Philippines—despite its name—has very good prices and is prominently displayed in many South African stores, but I do not trust their quality. I have seen too many Eurolux compact fluorescents fail while major-brand CFLs continue burning brightly. I buy almost all of my lighting supplies from Osram and Philips, and I believe the premium I pay for those brand names is compensated by their durability. (Eurolux, like Philips, does carry a three-year guarantee on their LED products; Osram LEDs are covered by a five-year guarantee.)

LEDs are falling in price, but for now, expect to pay R300 and up for a good-quality bulb. That may seem like a ridiculous price for a globe, but depending upon where it is used, LEDs can be a financially sound investment. According to Philips, Makro Woodmead and Strubens Valley and Pick N Pay Faerie Glen currently sell a 7 watt Phillips Master LED GU10 bulb for R299. My calculations suggest that over the course of 4 years, in a room where the lights are on 5 hours a day, this LED bulb is no more expensive than buying and using the equivalent 35W halogens at R40 each. After those 4 years, the LED pays a return on your investment. (The calculations ignore the cost of capital. You wouldn’t charge the environment interest, would you?)

If the bulb is in a location where it burns less frequently, it takes longer to pay for itself, and vice versa. At 3 hours a day, expect a 7 year payback; at 6 hours, the initial outlay is recouped in just 3 years. LEDs are improving rapidly, so the temptation is strong to wait. My advice is to buy a few now for a room where the lights burn longest, and gradually add more rooms as better and more affordable LEDs become available. Sometimes you have to spend a little to save a lot.

GeyserWise . . . . . . not saving in Power Save Mode

As far as I’m concerned, my GeyserWise thermostat timer paid for itself within a few weeks. Then it started costing me money.

The GeyserWise is an electronic device that replaces both a timer and the thermostat on an electric geyser element. As I have stated before on this website, a timer is an essential part of a hot-water solar system. The GeyserWise would appear to be the ultimate geyser timer, allowing the user to set multiple programs to turn the geyser element on and off, to see the temperature inside the tank, and to adjust the thermostat setting from a comfortable position several meters away from the geyser itself. No more crawling into the roof space with a headlamp and screwdriver.

I paid R1300 for my GeyserWise, including installation by an electrician recommended by the manufacturer. Here’s how it paid for itself so quickly. Monitoring the temperature inside my tanks, I started noticing that the water would cool off by a few degrees in the late afternoon every (more…)

Chris Yelland and the team at EE Publishers are the gurus of all things to do with electric power. So all South Africans would do well to pay attention to their analysis in this morning’s EE News: Brace yourself – the electricity price trajectory for years to come…
The article makes the point that when the National Energy Regulator of South Africa nixed Eskom’s proposed annual rate increases of up to 35 percent . . .

Many consumers breathed a sigh of relief, but a fact that received little attention at the time was the indication by NERSA that the 25% p.a. increases allowed for 2010, 2011 and 2012 would now likely continue after 2012.

The article later adds:

Irrespective of which scenario is considered, the projected electricity prices in the draft IRP 2010 show annual increases well above inflation up to 2021, and it would appear that the golden era of Eskom price increases at or below inflation will only arrive thereafter.

And concludes:

. . . take heart! Electricity prices should level off in about ten years time. Highlight 2021 in your diary as the dawn of a new era of Eskom price increases in line with inflation. Maybe…

I ran some of these numbers through a spreadsheet to see what they might mean to my electricity bill. For Eskom to reach the prices it originally envisioned before NERSA put a lid on annual increases, 25 percent price hikes will have to continue to at least 2014. Assuming that City Power of Johannesburg passes these increases on to residential users, this means that the 68 cents per kilowatt hour we pay today could leap to R1.66 in the next 3 years.

I don’t raise this issue to increase anyone’s blood pressure. What interests me is that this information completely changes any cost-benefit analysis of investments in energy efficiency at home. Back at my spreadsheets I find that  a solar hot water system that would pay for itself in 5 years at 68 cents a kilowatt hours, recoups the outlay in just 2 years at R1.66 a kilowatt hour. An efficient, variable-speed pool pump that makes sense as an investment over 7 years, suddenly makes much more sense by turning profitable in just 3 years.  LED lights that were expected to cover their costs in 6 years achieve that mark in 2 1/2 years.

I don’t think that every effort to make a greener house has to pay for itself. A little bit of financial analysis does help point out the changes that can make the greatest impact for the least expense, however. Eskom may not be doing our budgets any favours, but it sure is turning the cost-benefit analysis for eco-friendly investments green.

When I first wrote on GreenerHouse about dishwashers, I lamented that I could not find one with a hot-water inlet. For most of the year, I have an excess of solar-heated hot water sitting in tanks, so it is a waste for my dishwasher to be electrically heating cold water. At the time, I had been misinformed by a Bosch technical expert that the inlet to my dishwasher could handle a maximum of 40 degrees. Like an idiot, I hadn’t read the manual, which says that the inlet can take up to 60-degree water.

Water heated by flat-panel solar collectors does not tend to rise much above 60 degrees, and my kitchen is far—too far—from my water tanks to ever get to 60 degrees at the tap, according to my thermometer. (Vacuum-tube panels do often produce much hotter water, and may require a thermostatic mixer to keep temperatures at safe levels.)

So I recently asked my plumber to connect the hot water to my dishwasher. My hypothesis was that the thermostat inside the dishwasher would switch off the heating element more quickly with warm water entering the machine. Using a cold-water feed, this Bosch, A-rated model uses approximately 1 kWh per load at the 35 degree “Quick Wash” setting. After connecting the hot water, I recalculated the energy consumption, using the technique outlined here. It has fallen to 0.7 kWh per wash. Over the course of a year, this simple change should save about 100 kWh preventing some 100 kilograms of carbon dioxide from being released into the atmosphere.

If my dishwasher were located closer to the hot water, the savings would be far greater. In designing a new house, ideally the north-facing roof, solar panels, hot-water tanks, bathrooms and kitchen should all be as close as possible. If this is not possible, small-diameter Pex pipes can help overcome heat loss over long distances. (Combining Pex pipes and vacuum-tube solar collectors is asking for a meltdown, however.)

I compensate by running the hot water in the sink, usually while washing pots and pans, immediately before switching on the dishwasher. That way the water enters the machine hot for the wash cycle, though only slightly warm after the copper pipes have cooled the water for the two rinse cycles. One day I will try insulating the pipes and see if I get even better results. In the winter, when the sun does not always provide enough hot water, I will try to run the dishwasher in the late morning, so as not to deplete the evening supply of hot water.

Coincidentally, just days after my plumber had made the connection and before I had a chance to measure my results or write about it, a GreenerHouse reader published a comment here, reporting how pleased he was with his hot-water connection to his dishwasher. All green minds think alike.

Throne contender Venezia

Long ago on this website, I gave my seal of approval to the Compact dual-flush toilet made by R.A.K. Bathware. (And blew a raspberry at a dual-flush toilet that does not work as advertised.) For nearly 6 years now, my R.A.K. Compact has flushed dependably well over 9 times out of 10, for both 3 litre half flushes and 6 litre full flushes. I had no expectation of finding a better toilet.

Over the holidays, however, I stayed at a house that had recently fitted Venezia toilets by Lecico, an Egyptian company. Using seemingly insignificant amounts of water, these toilets made absolutely perfect flushes. They were so perfect, in fact, that I sometimes flushed . . . uhhh . . . “solids” using the half flush. Officially, the Venezia is a standard water-saving toilet, using no less than the Compact, but this would depend upon the settings of the mechanism inside the cistern. I am certain that these Venezias were using less than 6 and 3 litres per flush.

This gives me some confidence that Lecico’s ultra-efficient Riviera toilet, rated to use just 4.5 litres for a full flush and 2.6 litres for a half flush, will function properly. The Riviera is also more attractive than the Venezia. But just to be clear, I have never used a Riviera and make no promises for it.

I priced all three of these toilets at Plumblink, and the Lecico Venezia is the cheapest of the lot. Packaged with a basin worth a few hundred rand, it costs R1175, excluding VAT. For the toilet alone, the R.A.K. Compact goes for R1139 and the Lecico Riviera will set you back R1195.

These figures are rather small next to the savings you can expect on your water bill. If you are replacing an old 9 litre toilet, a family of 5 could save about R625 every year at current Johannesburg water rates, R780 if you regularly water a large garden, bumping your bill into a higher tariff. Heavy consumers paying Cape Town’s higher rates would save over a thousand rand each year.  Our dual-flush toilets have already paid for themselves more than once.

By the way, most ordinary lever-handled mechanisms can work as a sort of dual-flush mechanism with a deft touch. Simply lift the lever back up part way through the flushing process for a D.I.Y. dual flush.

The early summer cold-front that has been chilling Johannesburg for the last few days has me scratching my head. I measure my electricity consumption regularly and record it on a spreadsheet, and suddenly found that the household’s daily usage had jumped from about 15 kilowatt hours to about 25. Then we ran out of tea just a few days after we opened a box of 80 bags. Could there be a connection? Four children are at home studying for exams in the cold, and teacups have been piling up on their desks. With a thermometer, a stopwatch and a calculator, I set out to solve this mystery.

To raise a litre of water by one degree Celsius theoretically requires 0.0011 kilowatt hours, so heating my 1.7 litre kettle from tap temperature to boiling, 17 to 97 on my thermometer, should use 0.15 kWh. But since it took 3:48 to boil while using approximately 2750 watts, the actual consumption was more like 0.175.  (My Watts Up meter cannot handle appliances over 2000 watts, so I could not measure directly.) The inefficiency probably comes from the heat lost warming up the stainless-steel kettle itself—a plastic kettle might reduce those losses—and the delay between when the water reaches boiling and the kettle shuts off.

Of course, they don’t all share a pot of tea at once, so I used a spreadsheet to simulate two scenarios. In one, my children have suddenly become green angels, and measure out exactly one mug full of water into an empty kettle to boil. Under these ideal conditions, their additional 24 cups of tea a day would use just 0.59 kWh. The worst-case—and very common—scenario is to fill a kettle and boil it over and over again  until nearly empty before repeating the process. Under these circumstances, those same 24 cups of tea use nearly three time as much electricity, or 1.61 kWh. (Even after taking into account the warm water that is being re-boiled.)

My mystery is not entirely solved. The kettle could account for a sixth of the increase, but the rest must come from addition lights burning at desks, the refrigerator door opening and closing for study snacks, and those electronic devices that seem to take over study breaks.

Still, I’ve learned something useful. Changing kettle habits can make a significant impact on consumption. The Eco-Kettle is designed to make this simple, saving you from running back and forth to the sink to measure another cup of water. The water reservoir at the top of the kettle can release measured cups of water to the element at the bottom. It is available from a few sources in South Africa for R450 and up. Six people drinking 4 cups of tea a day with a full-kettle habit to break could probably save enough to pay for the expense in a couple of years.  I’ve seen a few complaints on the internet about durability, however, and I wonder if a simpler solution wouldn’t suffice. I plan to put a water jug next to the kettle and ask my family to measure out the water in their teacup before pouring it into the kettle. (Our kettle has a flat bottom. If yours has a raised element, it may need extra water to cover the element.) It should save them time, too. My stopwatch tells me that a cup of water boils in 51 seconds. A full kettle takes nearly 4 minutes.

While on the subject of kettles, I sometimes use ours as a back-up geyser. I try to keep the electric elements in my two, 300 litre solar-heated geysers switched off, and most days I don’t need them. But occasionally I have been seen pouring a few kettles full of boiling water into a bath on a winter night to keep my wife from grumbling about my solar fanaticism. This causes her to ask, “wouldn’t it use less electricity just to turn on the element in the tanks for an hour?” My spreadsheet provides the definitive answer. Boiling even five kettles of lukewarm water from the hot tap uses 2/3 of a kilowatt hour. The 4000 watt element on the geyser would use 4 kWh in an hour. There are times when a full kettle is green.