Appliances &Solar11 Feb 2011 01:15 pm

Dishwasher Plus Solar PanelsEqual SignGreen Smiley

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.

Appliances &Solar18 Nov 2010 02:35 pm

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.

Appliances30 Sep 2010 02:19 pm

Lights out for cold

When the water began pouring out the door of our ancient washing machine onto the kitchen floor, I finally accepted that it was time to buy a new one. During a previous, failed round of shopping for a washing machine, I was put off by all of the conflicting claims about the efficiency of different washing machines and the confusing range of options. Did I want steam cleaning? Would a hot-water inlet save electricity? But I relaxed when I realized that none of these complications really matter. Any washing machine with an A rating from the EU will be relatively efficient in its use of water. And if you wash in cold water, electricity consumption is practically a non-issue.

I discovered to my surprise, however, that this revelation does not suddenly make choosing a washing machine simple. At the first appliance store I visited, the basic Bosch washing machine that I wanted to buy did not have a cold-water option. The lowest temperature allowed was a warm 30 degrees. To buy a Bosch machine with a cold-water option, I would have to pay R2,700 more. The basic machine is efficient, with an A rating, but even at the lowest temperature setting, I would at least double my energy consumption compared to my old, inefficient machine on cold.

I also encountered a lot of resistance from salespeople about cold-water washing. The usual line is that the washing powders work better in warm water. This may be technically true but practically irrelevant. What I know is that in any line-up at school, my children’s white socks and white shirts look brighter than most of the others. My theory is that any advantage warm or hot water may have in removing grime is countered by the grey tinge that the whites pick up from colours that bleed, even if the wash is largely separated into light and dark loads. Besides, the latest Skip packaging says “works just as well in cold water.” The fact that our washing dries in the Highveld sun also makes it brighter than tumble-dried laundry.

At another store I did find LG and Samsung machines that allowed independent temperature settings, including cold. Both LG and Samsung get top marks for their washers in recent quality ratings by J.D. Powers. I chose the Samsung because its dimensions fit better under our kitchen counter.

I wish I could say that my new Samsung washer (model WF8500NHW) is the ultimate choice for cold-water washing, but I have encountered two disappointments in using it. The first is that each time I turn the appliance on, it resets to 60 degrees. I must remember to change it to cold before each wash. The second is that on one useful wash cycle, synthetics, it refuses to go to any temperature other than 40 degrees.

These obstacles are surmountable. We have become accustomed to washing on the longer, cotton cycle and resetting the temperature each time. My Watts Up meter tells me that I’m using less than 0.2 kilowatt hours per wash, which is a fraction of the consumption for a hot wash in the most efficient machine available. But I would advise anyone in the market for a cold-water washing machine to ask a lot of questions or watch a machine in action before handing over your money.

Appliances02 May 2009 06:18 pm

 Refrigerator vent clogged with dust  Refrigerator vent after cleaning

Before                                         After

I have always considered our refrigeration set-up to be rather modest. No bar fridge. No chest freezer. No massive side-by-side fridge-freezer. (That’s the least efficient configuration; freezer on top is the most efficient.) We manage to keep five people fed with a single, rather small, 300 litre LG refrigerator-freezer that receives an A rating for energy efficiency from the European Union.

So I was a little bit disappointed when I used my Watts Up meter to measure the actual consumption of this appliance recently and found that it was chewing through 2.5 kilowatt hours a day, about 10 percent of my household consumption. When I researched the issue on the internet, I saw numerous references to dirty coils lowering efficiency, so I pulled the fridge out of its slot in the kitchen. I feel a little embarrassed to publish the photograph above, because it is a stiff indictment of our housekeeping, but you have to see it to realize that when I say years of dust had clogged the vents, I really mean it.

After a quick vacuuming, I was eager to test whether the improved air-flow to the coils would lower my electricity consumption. I measured at night so that the comparisons would not be thrown off by family members opening the doors during the day. Consumption fell by more than 17 percent after the fridge was freed of its dust blanket. Since the condenser works much harder during the day than at night, the true improvement may be much larger. I have now set an annual memo on my Outlook calendar to remind me to keep the vents clean and my refrigerator green.

Appliances18 Feb 2009 05:43 pm

Watts up? Pro meter

I have a new toy. It’s called a Watts up?, and it will measure the watts used by anything with a plug, up to about 2200 watts. It will calculate watt hours, as well, which is essential for appliances that cycle on and off. Watt hours are what you and I and the environment pay for. Quite simply, a 1 watt device running for an hour has used 1 watt hour. The electricity meters on houses measure kilowatt hour, or 1,000 watt hours, and that’s what we pay for in our electricity bills. For each kilowatt hour we use, Eskom sends about 1 kg of carbon dioxide into the atmosphere.

I’ve been playing with my toy for about a week, and I now have a good idea of how much electricity is used by what.

Here, in no particular order, are some of my findings.

•Washing Machine: 214 watt hours for full load. My mother-in-law always believed that clothes fare better in a cold wash, so we have always set our washing machine on cold. (Who am I to argue with my mother-in-law?) The washing machine is rated at 2360 watts, so it might burn out my Watts Up meter if I tested a hot load, but my calculations are that if we washed in warm or hot water, that number would rise by 10 times.

•Philips 29-inch CRT Television. 73 watts on, zero on stand-by. You won’t find a big flat-screen LCD or plasma TV that uses anywhere near that little.

•DSTV Personal Video Recorder PVR: 29 watts. This is worse than it looks. Forget the fact that the PVR tells you it’s “going to sleep,” or “coming out of sleep.” It uses 29 watts all day every day, three-quarters of a kilowatt hour per day, 270 kWh per year. What irritates me is that the designers could have engineered a PVR that powers down the hard drive when it’s not needed, as my laptop does every time I stop using it for several minutes.


Appliances &Global Warming &Uncategorized25 Mar 2008 12:32 pm

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.

Appliances &Uncategorized26 Feb 2008 09:06 pm

My article on televisions and electricity consumption is now available on the Mail & Guardian website at this link. The previous post contains all of the practical advice that a television buyer could glean from the article, but the original text does provide more context. It also includes a salient comment by Professor Ernst Uken, head of the Energy Institute at the Cape Peninsula University of Technology.

Uken says households play a larger role in the South African power crisis than their overall consumption would suggest. The morning and evening spikes in power usage are caused by the domestic sector, he says, “and spikes are the reason for the power outages. The tail is wagging the dog.”

Appliances &Uncategorized22 Feb 2008 09:14 am

Perhaps you have heard of Moore’s Law. Named after the founder of Intel, Gordon Moore, it states that computing power of integrated circuits doubles every two years. In the latest issue of the Mail & Guardian, I have introduced what shall heretofore be known as Boroughs’s Law. Named after the founder of Greenerhouse, Don Boroughs, it states that for each additional ten inches in flat-panel television screen size, its electricity consumption approximately doubles.

I discovered this law by plotting the consumption of TVs sold in South Africa on a graph, and it’s the most important thing you need to know when buying a television. Because just to look at it, you might think that a 50 inch TV—manufacturers measure these things on the diagonal in inches—would use 20 percent more electricity than a 40 inch TV. You would be wrong.

Forty-inch TVs shouldn’t use more than 250 watts. (The worst ones use more.) Fifty-inch TVs typically use 500 watts, more than six 60-watt lamps. Boroughs’s Law works all the way through the range of television sizes available in South Africa, from 20 inches to 60 inches.

This tells you that the first thing to do is when buying a television is to convince your partner—or yourself—that you can get by with a TV one size smaller than the one you have been considering. A 32-inch LCD TV, which would have been considered large not many years ago, should use a reasonable 150 watts. That’s not much more than the average large CRT TV—the kind of TV we’ve all been using for the past few decades—and even less than the least efficient CRTs. (Cathode Ray Tubes.) Sony sells a 20-inch LCD which uses an amazing 60 watts. The incredible efficiency of LCD screens at small sizes—and only at small sizes—explains why they are the greenest choice for computer screens.

Once you have decided on a size, there is still a wide range of power consumption, even within the same brand of television. Thirty-two inch TVs, for example, vary in consumption from 132 watts to 380 watts. Televisions should come with big labels stating their consumption, and one day they will. In the meantime, there are only two ways of learning the wattage of a television: through the internet or checking the label on the back of the TV. If you are researching from home, try these websites:

Once you find a TV that interests you on the web page, click on “technical specifications,” or similar wording. The wattage is usually hidden near the bottom of the list.

You should be able to find a 32-inch TV using 140 watts, a 42-inch screen using 240 watts, or a 46-inch model using 270 watts. LCD TVs tend to use less electricity than plasma TVs. If you really feel that you must have a larger TV, the only models that use acceptable amounts of power are rear-projection TVs. Experts say that their picture quality is as good as flat-panels, they cost a lot less, and the Sony models use about 200 watts, all the way up to a 60-inch screen. They are bulkier, however, and will not be available for too much longer, as they are losing the battle for market share. This may lead to close-out bargains.

If you don’t want to sift through a hundred models, I suggest starting with the Philips brand, as they tend to be more energy efficient. I would avoid LG, as they tend to be more power-hungry and they often don’t state the wattage on the label at the rear of the TV. If you like Sony, and money isn’t much of an object, the European Imaging & Sound Association gave its most recent Green Television of the Year award to the Sony KDL-40D3000. That exact model isn’t available in South Africa, but its local equivalent is the 40-inch D Series Bravia model KLV-40D300A, which uses 180 watts.

Their voting panel looks at ease of recycling and other environmental issues in addition to electricity consumption, so this should be an all-around good choice if you need a big TV.

Or of course you could just stick with your existing CRT television. I checked my 2-year-old, 29-inch Philips CRT television, and it uses 73 watts. If you use an older TV, it is doubly important that you switch it off at the box, rather than using the remote to put it into stand-by. (This also reduces the chance of damage from a lightning strike.) Almost all new flat-panel TVs use one watt or less in stand-by, but older TVs draw enough power in stand-by that in a day you may use more electricity not watching TV than you do watching it.

Appliances &Uncategorized &Water Use/Greywater15 Nov 2007 06:18 pm


The 35 degree solution

For years I’ve had to avoid my wife, for fear that she would again ask me how long she must wait before I will replace our leaky, ineffective dishwasher. This Indesit was so old that the last few repairs have required salvaging used spares. I had been procrastinating that decision even though I knew that it would reduce wasted water and electricity. My procrastination had nothing to do with a fondness for mopping the floor or scraping crud off the bottoms of teacups. I simply feared the amount of research that would go into finding an energy-efficient, water-conserving dishwasher that gets dishes clean. I am happy to report that my new Bosch SGS44E12EU (also called the SGS43E02EU) arrived today, and the investigation was not quite as painful as I had anticipated.

Not that I got everything that I wanted. My first goal was to find a dishwasher that could make use of the spare hot water my solar panels produce for nine months of the year. Alas, a Bosch technical representative explained to me that no domestic washer has hot and cold intakes, and the intake valve on a Bosch dishwasher could not tolerate a temperature above 40 degrees. This would require me fitting an expensive mixer valve to cool the water before it entered the machine. Besides, he explained that the way modern dishwashers work is to start with cold water and gradually raise the temperature. Use hot water in the first cycle, he warned, and you will bake the food onto the plates. I gave up on that track.

The next step was to compare water and electricity usage of various dishwashers. In Europe, Australia and many other markets, this is a simple task. Each appliance is labeled with a large sticker showing energy consumption, water consumption and an overall A-G rating. Dishwashers in Europe get three ratings: one for energy consumption, one for washing efficiency and one for drying efficiency. The Department of Minerals and Energy has long been promising South Africans a similar system, starting with refrigerators in May of 2005. Two and a half years later, the only appliances with an energy labels are a few imports with their European label intact.

Still, through the Internet, brochures and the Which? website, it was possible to get information from overseas efficiency ratings. Bosch’s South African website, for example, clearly displays the European ratings and consumption data for all of its dishwashers. (Curiously, they don’t display that information for their tumble driers, which, like the vast majority of these energy hogs, get Cs.) All of Bosch’s dishwashers get European As for energy consumption, which means that they use less than 1.06 kilowatt hour for a standard 50 degree wash. Not coincidentally then, many dishwashers, including all of the Bosch dishwashers sold in SA use exactly 1.05 kWh. The one I chose also uses a modest 17 litres of water for a standard wash. The top-of-the-line SGS 46 E 28 GB uses a mere 12 litres. But it costs R6399, a full R3000 more than mine, which is a lot of money to pay to save the equivalent of less than a flush of the toilet.

More important, the upper-range dishwashers have 45 degrees as their coolest setting. The economical dishwasher I chose goes down to 35 degrees. My sister-in-law uses a Bosch similar to mine and says that she never moves it from that coolest setting. She doesn’t rinse anything before putting it into the dishwasher, and even sticky porridge bowls come out clean. I haven’t succeeded in getting the data from Bosch on the electricity consumption of a 35 degree wash, but I did my own calculations. Since it uses 1,05 kWh for a 50 degree wash, and since heating 17 litres of water by 15 degrees should theoretically require 0,28 kWh, the 35 degree wash should use approximately 0,77 of a kWh.

A while ago, I checked the consumption of my old dishwasher at home, using the same, moderately precise methods I used to check electricity lost to chargers, transformers, appliances on standby and other vampires. It used 1.35 kWh on its lowest setting and guzzled 35 litres of water. Worse yet, because it cleaned so poorly, we used many more litres rinsing dishes. This is a purchase my gardener will appreciate. (Why? See here.)

My dishwasher only gets a C for drying efficiency, but that’s because it doesn’t have the electricity-wasting drying feature. It should get an A+ for leaving that off.

If you want to read a good overview of dishwashing written with a sense of humour, check out the Appliance Advisor’s guide to green dishwashing. By the time you are finished reading it, you will be convinced never to rinse your dishes again before putting them in the machine.

But do you even need a dishwashing machine? Advertisements for dishwashers often claim that they use far less water and energy than hand washing. I’m not so sure. Washing carefully, with 5 liters of solar-heated rinse water in one sink and 10 litres of solar-heated soapy water in another, I could beat any dishwasher on energy consumption. But my new dishwasher is a big step in the right direction. And it’s a lot better for my marriage.

Appliances &Global Warming &Uncategorized12 Nov 2007 12:05 pm

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.