Global Warming04 Mar 2015 07:40 pm

Why should you take steps to reduce your tiny impact on this great big world? I heard a convincing argument in a documentary about air pollution that has taken China by storm. Chai Jing has an uncanny ability to approach environmental issues with both her heart and her head. At the end of Under the Dome she observes how she was affected after getting involved in the installation of a filter to reduce the particulate emissions of a restaurant near her home in Beijing:

“I suddenly felt like my feet hit the ground. It’s a difficult feeling to describe—you know full well that in the grand scheme of things, this is actually a small impact. But knowing that when one person is able to make a small contribution, they are able to actually make things better, their heart feels grounded. In the war between human beings and air pollution, this is how history will be made: When millions of everyday people, stand up one day and say: “No. I’m not satisfied. I don’t want to wait. I will not sit back. I will stand up and do something. Right now, right here, right in this moment, in this life.”

Hot Water23 Feb 2015 05:55 pm

Switched off geysers

Switched off

I’m no party animal, but I attended four social events this weekend. My takeaway from a dozen or so conversations is that South Africans are seriously looking for ways to save energy. People were telling me about their new efficient fridges and gas stoves. A property developer explained how Standard Bank is saving thousands of tons of carbon dioxide by generating its own power from gas in Rosebank.

One question came up at two different parties: Does it save energy to switch off the geyser for part of the day? This is a query I’ve heard so often that one could be forgiven for thinking that it was the Number 1 issue in energy efficiency. People take passionate stands on either side of the debate. One person told me that he’s saving hundreds of rands each month by switching the geyser on and off. Another said she had heard that it uses more electricity to heat the water back up than to keep it hot.

Here’s the disappointing answer to the most-discussed issue in home energy conservation:

It’s no big deal.

You can save a little electricity with daily switching, but you could save a lot more by lowering the temperature of your geyser thermostat, buying low-flow shower heads, or insulating the tank—not to mention the even larger savings from installing a solar water heater or heat pump.

If your geyser were perfectly insulated, switching would save nothing. Because it is not, the element will reheat the water from time to time even if no one is using hot water. If the element is off, however, the tank loses heat more slowly as the water gradually cools. All of that water has to be reheated when you turn the geyser back on, but because overall tank losses were lower than if the tank had been kept hot, it requires a little less energy than repeatedly heating the water over that same period of time.

What about the guy who said he was saving hundreds of rands? If your geyser has been off for several hours and you switch it back on, any shower you take or dish you wash before the water has been fully re-heated is saving you significant energy, because switching off and on is effectively lowering your thermostat setting. These savings can be large, but you could have saved that same energy more consistently and easily by simply lowering the thermostat on the geyser. Unconvinced? You can read more here.

Electrical engineer TC Venter has a long, technical article on the subject of options for saving electricity with hot water heaters in Watt Now and comes to this conclusion: “short switch-off periods (less than a day) do not really contribute meaningfully to energy saving.” But Venter did bring up one exception to this rule.

There is one special situation, if one thinks it through carefully, in which a timer can be used daily to eliminate practically all standby power. If the occupant of the flat is single and a creature of habit, who only needs hot water to bath or shower at 07:00 each day, a small (50L) geyser could be run like an electric kettle: an electronic timer could be set to switch the geyser on for one hour at 06:00 every morning, to ensure hot water at 07:00, but not to reheat the geyser after its hot water has been used. The geyser remains cold until the next morning at 06:00, thus no standby power is required.

Of course switching off the geyser when you leave home on a trip can add up to real savings. Switching off during Eskom’s peak hours of 5 to 9 pm is also good for the country, if not for your utility bill. And timers are essential with solar water heaters to avoid using electricity to heat up the tank after morning showers, just before the sun has a chance to do its work. Finally, if you really want to switch your old-fashioned electric geyser on and off every day during idle hours, go right ahead. Just don’t imagine that your hot-water electricity consumption is solved.

Solar20 Nov 2014 10:33 am

I get a lot of questions about rooftop solar photovoltaic panels. Even people who haven’t really started investing in energy efficiency are eager to consider spending their savings on solar PV. I understand. There is something sexy about generating your own power.

I rarely write about the subject here because I haven’t purchased PV panels for one very good reason: photovoltaics should always be the last energy investment for a home, not the first. You can save more electricity at a lower cost with other expenditures: LED lighting, solar hot water, heat pumps and variable-speed pool pumps, to name a few.

But this is a good time to look closely at the numbers for two reasons.

1. PV panel prices have dropped significantly in the past few years.

2. My Green Home has given me a window on real-world results for a house with solar PV.

Not too many years ago, an executive in the solar industry in South Africa admitted to me that even at wholesale prices, it would not pay for him to put panels on his own roof. But for the past several years, PV module prices in South African have been falling by about 22 percent a year. Many installers are also keeping prices down by recommending systems with no battery storage, since batteries greatly increase costs both up-front and down the line. (Batteries generally do not last as long as PV panels.) Without batteries, you are not protected from load-shedding and blackouts, but you are supplying some of your own clean electricity at a more reasonable cost.

This is the kind of simple, grid-tied system installed for My Green Home at the Ngewanas’ home in Cape Town. I have access to detailed metering data from the house and have used it to calculate electricity production for the last three months and to extrapolate those results to create a projection for the annual kilowatt hours to be generated by the system. (Seasonal variability was factored in using the monthly data from this Soventix commercial PV installation at Blaauklippen Vineyards.)

The Ngewana family has a small system, with one 255 watt panel connected to a 230 watt inverter that creates AC current from the panel’s DC output. On every sunny day, it produces at least 1 kWh. My calculations project that it will produce 400 kWh in a year. The Ngewana family pays R1.54 per kWh, so the panel will save them R615 in the current year.

That’s mahala money for the Ngewana family, since the panel was sponsored by Citrine Energy. But if you had to pay for it yourself, Citrine would charge about R10,500, and the system would take 10 full years to pay for itself at the anticipated rates of tariff inflation. It’s a fairly safe investment, since polycrystalline silicon panels generally last much longer than 10 years. But you will need patience if you are counting the days until you’ve paid off your investment.

The rate of return would be better for South Africans who live in sunnier regions or pay a higher tariff, but at todays PV prices, it will take several years to cover the outlay under most circumstances. The situation will improve dramatically when South African utilities begin to pay homeowners for any excess electricity they feed into the grid, which is called a feed-in tariff. This will also allow homeowners to buy larger panel sets that cost less per watt. (Some homeowners do this already by running their disc meters backwards, but this is illegal.)

At My Green Home, we had to carefully size the system to produce no more electricity than the home would ever use during the sunny part of the day. (Approximately equal to their 300 watt variable-speed pool pump.) With the pre-paid meter at that house, kilowatt hours add up no matter which direction the electricity is flowing. They would have paid for any excess kWh they contributed to the grid!

So has the time arrived yet for generating electricity on your roof? It depends. If saving money is your only priority, wait a couple of years until prices fall further or your utility offers to buy your excess electricity with a feed-in tariff. If, however, you have already invested in making your home energy efficient, and it would give you pleasure to know that some of your electricity is clean and carbon-free, the time is now.

Global Warming28 Oct 2014 12:27 pm

17 kWh/m2/year. My Number.

17 kWh/m2/year. My latest “number.”

The 49M campaign for saving electricity has launched a new calculator that allows any South African household to Know Your Number. I tried it out and found that it is by far the easiest way to get a reasonable figure for your home’s kWh/m2/year, which is your “number.”

Earlier this year, I wrote a guide to calculating this figure for the Green Building Council’s My Green Home website. The guide is still worth using if you want a more precise calculation for a full year, and it can help you work out the square meterage of your home if you don’t already know it. The advantage of the 49M calculator is that you only need to know your m2 and kilowatt hour consumption for a single month. It works out an annual figure for you, taking into account the generally higher electricity use in winter.

I tried several months on the calculator and all results were within a reasonably accurate range of 16 to 20. My manual calculation for all of 2013 had been 21, and my consumption has fallen a little since then.

Why would you want to know your kWh/m2/year? For one thing, it’s the most reasonable way to compare two houses of different sizes. You can use it to benchmark and see how much you might be able to improve. Second, any effort to monitor your kWh will help you save, just as you are more likely to lose weight if you step on a scale from time to time. Greenerhouse has a spreadsheet that can also help you monitor your electricity from your meter.

On knowyournumber.co.za, you can save your results, track them month to month and even share them on Facebook. The website sets benchmarks for you in the form of letter grades. Mine was an “A”, two notches short of an A++. It seems I still have work to do.

What’s your number?

Lighting &Solar06 Oct 2014 03:13 pm

It’s official: electricity tariffs will not rise just 8 percent – as had been promised – for the next few years. The National Energy Regulator of South Africa (NERSA) has granted Eskom a 12.69 percent increase for next year. Supposedly it’s a once-off exception, but don’t count on it. An article in today’s Business Day quotes several economists predicting years of high electricity inflation. Here’s Azar Jammine, chief economist of Econometrix:

“I wouldn’t be surprised to see this rate increase being repeated in the following four years (after next year). To be fair, if we are to get over this energy crisis we do have to increase tariffs”

This is bad news for consumers’ wallets of course, but you could look upon it as good news if you are thinking about investing in energy efficiency. A tariff of R1.50 per kilowatt hour – a rough median for suburban South Africans today – reaches R2.72 after 5 years of such increases.

Consider LED lights, for example. If you spend R1000 on 10 LED downlighters to replace halogen bulbs that are used 4 hours a day, you would expect to save R5717 over 5 years with 8 percent electricity inflation. Bump that up to 12.67 percent tariff increases and the savings leap to R6274. A solar water heater that would normally take 4 to 6 years to pay for itself reaches the breakeven point a half-year sooner.

The news from Eskom gets worse and worse, but the prospects for saving energy just keep getting better.

Appliances &Global Warming24 Sep 2014 03:02 pm

9 kilogram LPG gas bottle BP© 2014 Don L BoroughsEqual SignHigh31 Plates


We use our gas braai very regularly, not just on National Braai Day. In part this is because we like the taste and simplifies the kitchen clean-up. But it also helps reduce our electricity consumption. I try to avoid turning on the oven to frequently, since it can burn through about 2 kilowatt hours in one meal, which is a daily increase of about 20 percent from our low base.

Still, a question nagged at me each time I fired up the braai. How do I know I’m not using more fossil fuel and creating more carbon-dioxide emissions using that gas braai than I would with the electric oven? And how much is the gas to cook one meal costing me?

I finally have some sort of answer. Over the course of 4 months, I kept track of every meal cooked on a single, 9 kg bottle of liquified petroleum gas (LPG) until it ran out. I had cooked 31 ½ meals. (Thank you to the microwave oven for finishing off the half-cooked meal.) These ranged from a single fish to large meals including grilled vegetables and potatoes for Sunday lunches with guests. It wasn’t quite a scientific measurement, but it allows for some rough calculations.

The LPG bottle cost R250, so per meal I used R7.94 worth of gas. If each of those meals had rather used 2 kWh of electricity in the oven, the 31 ½ meals would have cost between R75 and R118, depending upon the local electricity tariff. So I am sorry to report that using the gas braai does not save us money compared to the electric oven. If we lived in a Joburg suburb with Egoli Gas, however, a braai using piped gas would be cheaper to use than the oven. And LPG is still less expensive than using charcoal.

(This is not the same as comparing a gas oven to an electric oven. A gas oven will be more efficient than a gas braai because it is better insulated and opened less often. For a comparison of gas vs. electric stoves, see this post.)

What about the environment? Gas burns cleaner than the coal used by Eskom, and using a fuel directly for heat is more efficient than using it to generate electricity. I still held out hope that my gas braai would come out on top. Further calculations showed that for a 2 kWh meal in the electric oven, Eskom generously donates 2.14 kg of carbon dioxide to the atmosphere and the climate. But the 286 grams of LPG I burned for each of my meals released less than 0.9 kgs of CO2. With less than half the greenhouse gas emissions, the gas braai wins cleanly.

Happy National Braai Day.

Lighting02 Jun 2014 12:47 pm

My Green Home Guide To Globes

Let’s start at the very beginning

Not sure of the difference between incandescent and halogen globes? Wondering where to use LEDs, and where CFLs are better? (Or still confused which is which?) Do MR-16 and GU-10 sound like the names of weapons to you?

Have no fear. I have just written a five-page, illustrated Guide to Globes for the My Green Home website that will clear away the confusion. It has eight simple buying recommendations according to the following common situations:

• Replacing 60 watt incandescent bulbs
• Replacing 100 watt incandescent bulbs
• Replacing low-voltage, MR-16 halogen downlights
• Replacing mains-voltage, GU-10 halogen downlights
• Replacing downlights on a dimmer
• Installing security lights
• Buying new ceiling fixtures
• Replacing standard bulbs in enclosed fixtures

Although LEDs are usually the best option, in some situations other globes make more sense. The guide also shows what to look for when reading the complicated labels on bulbs. And it is essential reading if you are shopping for fixtures, so that you buy those best-suited to energy-efficient globes.

At My Green Home, the Ngewana family has cut the electricity going to their lighting by 74 percent with this kind of advice. I would say that the Guide to Globes will pay for itself very quickly, but it’s free. Read the Guide to Globes here.

Appliances &Pool04 Apr 2014 05:42 pm

Spread from March 27, 2014 issue of YOU magazine.


Most of the advice in the YOU magazine article requires some planning and spending. But I included a box with my suggestions for saving energy immediately and at no cost.

Quick Savings:

1. Plan meals that don’t involve the oven; it uses much more electricity than the stove or microwave. We try to use the oven no more than two times a week.
2. Wash laundry in cold water, and only on sunny days. A clothes drier might be the biggest energy hog in your home.
3. Avoid ironing wrinkles that will never be seen. Underwear, fitted sheets, pyjamas and exercise gear don’t need the watts wasted on them.
4. Ditch the beer-fridge, chest freezer and ice machine. Unless you’re running a bar and living off last winter’s hunt, you can probably get by—like us—on one refrigerator/freezer.
5. Keep a jug of water next to the kettle, and pour in just enough for your next cup of tea.
6. Ignore the conventional wisdom that a pool pump must run 12 hours a day. Eight hours is sufficient in summer for my small pool, and just 1 to 3 hours in winter.

Heating and Cooling &Lighting &Pool &Solar03 Apr 2014 03:51 pm

Spread from March 27, 2014 issue of YOU magazine.


If you would like to read directly from the pages of YOU magazine about my house and how we cut our electricity consumption by 75 percent, click on the image above to load a pdf of the article.

If you would rather read it within this post, here are the nuts and bolts of the article’s advice in the orginal, unedited form. (If you want the personal tidbits about my family added by the editors at YOU, you’ll have to read the pdf.)

LEDing lights. Compact fluorescent lamps are no longer the latest, greatest and greenest. We’ve switched most of our lighting to high-tech LED globes that have a more natural tint, last a lot longer, and use only 1/6 to 1/10 of the power gobbled by ordinary incandescents.

When I first started buying LEDs to replace halogen downlights, I paid R250 per bulb for this new technology. Still, I calculated that they could eventually save me money in heavily-used rooms like the kitchen.

But LED prices have been plummeting. Recently I bought the same bulb for R50. These will pay for themselves in less than a year, even if used only a couple hours a day.

LEDs are now available in nearly every shape and size, though many globes still cost more than R100. Look carefully at the packaging for an equation that indicates the low-wattage bulb’s brightness compared to an ordinary incandescent, such as 10W = 60W.
Personally, I stick with established brands such as Osram and Philips. I have more than 50 LEDs lighting my house, some for more than two years, and not one bulb has died yet.

Penny-Pinching Pool Pump.
Pool chemicals seem expensive, but you may never know how much you are paying to run the pump. A 1.1 kilowatt pump working 12 hours a day could add R8 000 to your annual electricity costs. I pay a tiny fraction of that, with the best-kept secret in home energy savings: a variable-speed pool pump.

Variable-speed pumps save watts because they only run at full power for backwashing. During ordinary filtration, a mere 175 watts powers the Viron P300 pump supplied to me by AstralPool. Most installers still do not keep variable-speed pumps in stock, but they can find one. All of the major pump suppliers, including Speck, Zodiac and Pentair Kreepy Krauly, manufacture at least one energy-efficient pump.

Expect to pay R7 000 to R14 000 up front, compared to R2 000 for an ordinary pump, but you should earn all of that money back within a few years as you enjoy lower utility bills. What’s more, variable-speed pumps are whisper quiet and long lasting.

Sun Bathing. It’s no secret at all that a solar geyser is the most important step for homeowners who want to save electricity. Hot-water panels cut our utility bills by about R6 000 a year. Still, most South Africans continue to heat their water with traditional electric geysers—and pay for it every month. Let’s take a look at the main causes of resistance to going solar.

“I’ll wait ‘till my geyser fails.” When your geyser bursts or dies, you will need a quick solution. Installing solar takes time. It makes more sense to put up solar panels before your geyser gets into trouble.
“My uncle had trouble with his hot-water solar panels.” A lot of fly-by-night installers importing cheap panels have popped up recently. Insist on SABS approved panels as a first step, but also use an installer who has been in the business five years or more and a panel manufacturer with at least that much experience in South Africa. My nine-year-old flat panels have been problem-free.
“I’m confused by the different solar systems available.” At the risk of oversimplifying, this is my advice: Ask for an indirect system that first heats glycol, which then heats the water. Use tanks meant for solar, not something jury-rigged onto your old geyser. Larger tanks are worth the expense; I have 600 litres of storage. Ask for flat panels, unless your roof gets limited light. Evacuated tubes tend to overheat in the summer and are more vulnerable to hail.
“I don’t have a roof that gets any sun.” That’s fine. Replacing a traditional geyser with a heat-pump will save almost as much electricity as a solar system can.

Central heating, SA Style. When we moved into our Johannesburg house, it had five electric heaters. A contractor suggested we replace them with electric underfloor heating throughout the house. Back then, electricity cost less than 30c a kilowatt hour.

It gives me chills just to think of the damage five electric heaters or—worse yet—underfloor heating could do to our winter electricity bills today, at well over a rand a kWh.

I grew up in a centrally heated home in America, but I cannot see the logic of heating every room in a typical South African home, where the cold continuously leaks through uninsulated windows, walls and ceiling.

Instead we have returned to the old tradition of keeping just the centre of the house cozy, where we gather in the evenings. Then we sleep snugly under down duvets, hot water bottles at our feet.

But we use modern technology in our old-fashioned gathering place. An ultra-efficient Rinnai ventless gas heater is our go-to for quick warm-ups, especially in the mornings. Every evening I build a wood fire in a state-of-the-art, closed-combustion fireplace that creates a surprising amount of heat.

Unlike my LEDs and pool pump, the savings from evicting electric heaters from the house will take several years to cover the up-front costs. Bottled gas is not cheap. And a good quality fireplace insert or wood stove costs more than R20 000. (An open fireplace sends too much heat—and smoke—up the chimney to be efficient.)

But I cannot put a price on the warm ambience of our wood fire, which draws the children out of their rooms and into the lounge. Conserving electricity isn’t just a way to save money and the environment; it brings our family together.

Solar21 Mar 2014 09:56 pm

YOU Magazine 27 March 2014 Huisgenoot magazine 27 Maart 2014

In either taal

If you wade through the pages on Oscar Pistorius and Beyoncé in the issue of YOU magazine that hit the newsstands today, you will find an article on page 130 about Greener House.

By next week I will be able to reprint full the full text of the article, which is full of advice about saving electricity in the home. For now I will focus on a few key points about solar that were shortened or cut in the editing process.

In the original text, I decided to take a bold stand in order to simplify the many choices facing a homeowner who wants to install solar hot water panels. The uncut version refuted four of the excuses commonly used by those who haven’t gone solar:

“I’ll wait ‘till my geyser fails.” When your geyser bursts or dies, you will need a quick solution. Installing solar takes time. It makes more sense to put up solar panels before your geyser gets into trouble.
“My uncle had trouble with his hot-water solar panels.” A lot of fly-by-night installers importing cheap panels have popped up recently. Insist on SABS approved panels as a first step, but also use an installer who has been in the business five years or more and a panel manufacturer with at least that much experience in South Africa. My nine-year-old flat panels have been problem-free.
“I’m confused by the different solar systems available.” At the risk of oversimplifying, this is my advice: Ask for an indirect system that first heats glycol, which then heats the water. Use tanks meant for solar, not something jury-rigged onto your old geyser. Larger tanks are worth the expense; I have 600 litres of storage. Ask for flat panels, unless your roof gets limited light. Evacuated tubes tend to overheat in the summer and are more vulnerable to hail.
“I don’t have a roof that gets any sun.” That’s fine. Replacing a traditional geyser with a heat-pump will save almost as much electricity as a solar system can.

Even this unabridged advice may seem too short to account for the many configurations possible in solar hot water systems. I well understand the urge to find a custom solution that maximizes efficiency. But for those who will only make the leap to solar if it is simple and safe, these guidelines point in the right direction.

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