October 2014


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.