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Energy Efficiency Blog

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Archive for October, 2008

Oct 17

(with a big-up to Pete Dormand of Newcastle City Council first made this point…)

Efficiency is not sexy. Having a 6 star fridge does not get you any green street-cred compared with having a big shiny solar panel on your roof for the neighbors to ooh and aah at. But efficiency is by far the cheapest way to reduce emissions, which means that before spending thousands on solar panels, households should do everything they can to see if they could spend that money on efficiency improvements that would make a much bigger difference to reducing emissions per dollar.

example: cost of 1kw solar panel installed = $12,000, energy produced in one year = 1500kwh, cost per kwh saved per year = $8

But spend an extra $220 on a more efficient washing machine and save 548kwh per year, cost per kwh saved per year = $0.40

Energy efficiency here is 20 times cheaper!

Justification of the efficiency numbers using sokitt’s clothes washer efficiency comparison tool.

If you are looking to buy a top loading washing machine, you can pay $704 for a cheap 1.5 star one (just sort by energy rating and top-loading style and scroll to the bottom of the page)

But if you pay an extra $220 for the top rated top loader (3.5 stars) you will save $955 in electricity over 10 years. (look at the clothes washer at the top of the sokitt comparison grid when sorting by energy rating)

My opinion: the government (or a forward thinking retailer) should provide an interest free loan to cover the extra $220, so no-one has to buy the cheap, inefficient one.

Oct 13

Next to get the power meter shoved up its jacksy is the goggle box.

Last night we had a baby sitter round (we went to a Michael Franti concert :-) ) and she watched TV solidly from 8pm to midnight. So the profile might be a bit atypical, but here goes anyway.

The power meter tells me that over the last 24hrs my 28 inch CRT TV used 0.576kWh of juice.

Here’s the power profile:

My TV\'s power use over 24 hours

My TV's power use over 24 hours

You can see the big chunk of viewing when the babysitter was here. The TV uses about 80 Watts when it is on. You’ll also see that it uses zero watts when we are not watching, because we are in the habit of switching it off at the wall.

There’s not a lot of scope to reduce our energy use except watch less TV (which isn’t a bad idea).

At least we’ve got an efficient TV. A similar sized plasma would use at least double the power.

P.S. The government announced earlier this year that they are gonna put energy rating stickers on new TV’s. Great news.

Oct 08

Here’s the energy profile over 24hrs for my Whirlpool AWM6100 clothes washer:

The Watts sucked by my clothes washer

The Watts sucked by my clothes washer

This shows that it uses 2W (about $2 per year) in stand by which is pretty good. And you can also see that we used the clothes washer twice that day, which is pretty typical for us with 2 kids.

In one day we used 1.092 kWh of electricity washing clothes – or 398kWh per year. That’s 40% of 1 person’s budget 0f 1000kWh per year or 10% of our 4-person budget.

The really interesting thing about the profile is that almost all the energy is used to heat the water in the washing machine, as can be seen from the big spikes at the beginning of each cycle. Let’s zoom in on one wash:

Zooming in on one wash

Zooming in on one wash

So almost all the energy is in the heating of the water at the beginning of the cycle – and this was for the coldest wash setting on the machine – 30 degrees!

With the water heating – each wash uses uses 0.47 kWh. If we remove the heating this drops to 0.15kwh, less than one third of the energy, and remember this is for a cool wash.

So if we wash twice per day, we could save 290kWh per year by washing cold. Is this practical?

Well here in sunny Australia there’s a detergent called Cold Power and a quick call to the manufacturer’s helpline found out that they recommend 20 degrees Celsius as the optimum temperature.

Unfortunately my washing machine only goes down to 30 degrees. So if I want a cold wash then I will have to buy a new machine!

One other question that I need to find the answer to. Is a a cold wash done with zero heating, or is the water heated to a minimum temperature? I’ll get on to the manufacturers and find out.

I’ve just added a feature to sokitt that allows you to filter washing machines to only show those that are cold wash compatible. I think you’d be crazy to buy a new machine that doesn’t let you take advantage of cold wash detergents. If you are looking for a new machine this feature can save you hours of research.

Another feature I’ve added is a filter to only show washing machines with dual connections. That is: a hot an cold water connection. If you have solar hot water, then this is essential, as it means you can use solar thermal energy to directly displace 80% of the electricity that your washing machine would use on a hot cycle.

Sadly if you ask sokitt to show all clothes washers with a dual connection AND cold wash compatibility with an energy rating over 4 stars… there aren’t any!

But if you reduce the energy rating required to 3 stars and do another search about 20 washers are available. For some reason they are all top loaders.

The counter intuitive thing is – if your hot water is solar, then dual connections are more important that the energy rating! If this is you – then I would use sokitt to choose a machine with a low “Cold Wash kwh per year” and a high water rating, and a dual connection and not worry about the energy rating. The “cold wash kwh/year” is the energy the machine will use without heating the water. As long as this is low, you will use very little energy to wash your clothes thanks to the heating from the sun.

As for me, sokitt tells me I can get a 4 star water and energy efficient front loading washer with a cold wash program for $599. This uses 200 kwh/year on a cold wash if am using it twice per day. I reckon I can get $100 for my old washer, so the opportunity to save electricity with the washer is:

$499 to save 200kwh/year

Again, I’ll wait until I’ve audited every appliance and then work out where my limited funds will best be spent to save the most electricity with minimum dollars.