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Energy Efficiency Blog

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Archive for July, 2008

Jul 27

The cliffhanger in the last post was… How does my fridge’s performance compare with when it was brand spanking new?

This is a really important question if you are going to make an informed decision about reducing your electric bill, so we’ve been busy developing a database backend for sokitt that pulls historic energy performance figures for appliances from the energyrating.gov.au site. Yes that’s right, pick yourself off the floor, there is a government website out there that actually contains really valuable data! Data input by men in white suits who spend their Canberra days torture testing fridges, dishwashers, dryers and clothes washers to decide how many stars to put on their energy rating sticker.

So I can put my fridges make and model: Fisher & Paykel E249T into sokitt and it shows me the ‘as new’ performance of my fridge:

1.5 Stars - Oh Dear!

1.5 Stars - Oh Dear!

So, when new, my fridge was guzzling 691kWh per year costing $1300 bucks over 10 years in Energy (sokitt assumes electricity will go up by 5% a year – but this can be changed in Advanced Options) and was Rated at 1.5 stars. How embarrassing!

My bluetooth power meter told me that it is currently using 891kWh per year: that’s 200kWh per year I’m piddling down the drain.

I kinda knew that my fridge should be maintained – but this has shocked me into getting off my ass and doing something about it. So I defrosted my fridge (there was a lot of ice in the freezer) and re-seated the door seals that had come off in places and re-measured my fridges performance with my wireless energy meter. The graph of Watts vs. time over 24 hrs looks like this:

save energy - defrost your fridge!

save energy - defrost your fridge!

That’s better – at least now the compressor switches off regularly (although it is still swutched on more than it is off – but hey it’s a crappy 1.5 star fridge whattdya expect?).

(by the way I think the really high spike is the auto-defrost where little heaters suck heaps of juice in an attempt to melt the ice off the coils)

Extrapoloating the kwhs measured over 365 days tells me that my fridge now uses 722kWh per year which is within 5% of it’s new performance and is as good as I can expect from a fridge this old.

So by defrosting my fridge overnight and pushing some door seals into place I’ve saved nearly 200 kWh per year. Not bad, but get this: If I’m typical for an Aussie household – multiply that by 10 million Australian homes and you’ve saved 2 million MWh (a MWh is 1000 x kWh). To put that in perspective that is 20 times the total amount of electricity generated by every solar panel in Australia in 2006. Oh yeah – the power of energy efficiency.

But before I get too smug – my fridge is still pretty crappy on the energy front at 1.5 stars. Hell you can buy 6 star fridges these days.

Before sokitt the place to go for appliance comparisons was www.energyrating.gov.au . This has some amazingly useful data except for one fatal flaw – it doesn’t display the prices of the appliances. It drives me freakin’ mad because you see your dream 6* fridge, then have to spend 10 minutes on Google looking for the price and you find out it costs $4,000 dollars and the freezer is another 2 grand on top!

Anyway, we’ve developed an appliance energy comparison tool that mashes up price and energy data and lets you compare current appliances with your old ones. When I put my fridge model in I find out (in about 5 seconds flat) some interesting things (to a tight-ass efficiency geek like me anyway):

See the comparison with my crappy fridge here

  • The best payback for a similar size fridge is 10 years (assuming 5% increase per year in elec prices) and that is actually a 3.5 star fridge. (pay back is how long it would take for my savings in my bill to pay for the fridge)

  • If I sort the list by Energy Rating, I see that the highest rated fridge on the market a similar size is a 4.5 star whirlpool for $879. (can someone tell me why you can’t get a 6* fridge that’s not the size of a house?)
  • The cheapest 4 star fridge is $642. I can’t begin to tell you how hard it is to answer that question without this tool!
  • So should I buy a new fridge? You think it would be a no-brainer with a 1.5 star guzzler…

    But I can’t answer that question until I have measured every electricity using device in my house and I have worked out the cheapest way to get my electricity down. There may well be much bigger wins to be had in terms of dollars per kWh saved where I should focus my limited funds first. We’ll see what the wireless power meter says over the next few weeks…

    Jul 23

    Over the next few weeks I’m going to post every day as I go through every appliance in my house with a prototype version of the sokitt toolkit and take action to get my electricity bill down.

    The point of all this is to show you a real life example of how a typical family can painlessly and cheaply get their electricity below a target usage of 1000kWh per person per year. If “kWh” means nothing to you think of 1kWh of electricity as 15 cents, so 100kWh of electricity is $150 worth.

    Why get your per person use down to under 1000kWh?

    Well the average per-person use of electricity in Oz is 3,000 kWh. So the average person should be able to reduce their bill by 2,000 kWh. That’s $300 per year per person. $1200 bucks per year for a 4 person household. And bear in mind that electricity is probably gonna double in price over the next few years…

    The other reason is that we could shut down 2 or 3 of Australia’s biggest dirtiest power stations if we all did this. Which would be nice.

    Anyway back to my fridge. 24 hours ago I plugged it into my sokitt compatible power meter. This wireless power meter logs the power that the fridge is using every minute and beams it to my computer (using Bluetooth).

    Here’s a graph showing how many Watts my fridge sucks every minute for 24 hours:

    fridge power

    fridge power

    The y-axis on this graph is Watts. The high black areas are when the compressor is running, you can see that the compressor is on a lot more than it is off. This is bad news – fridges are designed to have the compressor switched on for less time that they are off. It looks like my fridge has become a bit of an energy guzzler and has to keep the compressor on for ages to keep the temperature down.

    sokitt takes this data and can tell me the following:

    1) my fridge is using 2.44kWh per day
    2) this is 891kWh per year
    3) it’s costing me $131 per year to run
    4) it is the equivalent of a zero star rated fridge in 2008 terms! (it’s only 5 years old!)

    Remember my budget is only 1000kWh per year per person, so my fridge is using 90% of 1 person’s allowance!

    Now what I really want to know is: how does my fridges performance compare with what it was when it was brand new? And what are my options for buying a much more efficient fridge? Should I buy a new one or get this one fixed up?

    sokitt can answer all those questions too. I’ll show you how in the next post.