23 January, 2009

Your Electric Bill - part 2

How to understand it, what to do to make it smaller.
Last article, I posted a typical electric bill and decoded some of the obscure bits.  Then I laid out the recording phase of reducing your energy bill, where you investigate what your appliances draw, how long they operate for each day, etc.  You should have a notebook page or three full of figures, notes, and observations.  If you don't, it's probably time to go back and re-read that article, and do take the notes.  
Now for a few thoughts to reduce that energy bill.
How do I reduce my energy usage?
Look at your notepad.  The four most common things that increase your energy bill are listed here.  I bet you'll have found at least two of these things in your own list.
  1. Environment Climate Control.  By this, I mean air conditioning, heating, and use of fans.  And most of the time, you can markedly reduce this and save energy, money, and environment.
  2. Refrigeration and Food Storage.  Whether you have a single refrigerator or a huge pigeon pair plus a freezer in the garage and a coolroom pantry, there are still energy saving tips.
  3. Computers and computer related devices.  A surprisingly large portion of your energy sheet will be consumed by computers and peripherals.
  4. Vampire power.  By now most people are familiar with the term "vampire power."  It means the current flowing when a device is "switched off" but still on standby so that you can save getting up, and instead awaken the device with the remote control.
I'll tackle these in order.
Air Conditioning Tips:
When you checked your A/C, you would have found one of several types.  A refrigerated air conditioning system, which is best in terms of keeping the house cool, but expensive to run.  An evaporative cooler system, which is much cheaper to run but won't get as cold as a refrigerated system.  And then there are the newer so-called "inverter" systems which are a refrigerated A/C but save you a little on power - and more if you take the advice I'm about to give.  One other important difference, refrigerated A/C systems can also come as a "reverse cycle" unit that heats as well as cools.
The only type of air conditioning system which you should have running with doors or windows open is the evaporative style cooler.  These have a large (generally 600W - 1200W) motor for the fan, and a small (< 100W) motor to pump water over the cooling screens.  These systems actually need windows or doors open, and the best place to do that is on the side away from the prevailing wind, so that the waste air is sucked out of the house and thus assists the evaporation and the fan.  There's little practical difference between running such systems in "air only" and "cooling" modes, because in cooling mode you're only turning on a small water pump.
If you have a refrigerated A/C system and any doors or windows open, then you deserve the electricity bill you're going to get.  These systems consist of two motors:  A) a fan to move air, as for the evaporative system above, but much smaller because these systems don't need to move quite the volume of air which evap systems need to move, and B) a motor to drive a compressor to provide the cooling.  The fan motor will be running constantly to move air, and the compressor will cut in each time the thermostat clicks on due to the air over it being too warm.  
The compressor motor will draw the majority of the energy, so it's important to keep heat out of the air.  That means, if you have a window or door open to the outside, the thermostat will be on almost contuinuously, and so will that compressor motor, chewing through your dollars...
Keeping the heat outside, by closing doors, drawing curtains on the sun side, etc, should be your primary concern.  The less times the compressor has to run each day, the less will be your energy bill.  Note that by setting the thermostat for not quite so cold a temperature will also result in substantial savings.  The primary best thing a refrigerated A/C does is to remove excess humidity from the air, and that will actually make warmer air seem sufficiently cold, so sometimes just 5 degrees below outside temps can be sufficient.  
The same sorts of things need to be applied in the case of heating, or running the A/C in reverse cycle mode - keeping the outside out is your main priority.
One exception is the new breed of "inverter" A/C units.  These don't just switch the compressor on and off, they can vary the amount of cooling effort of the compressor, so that you don't get the heavy and expensive "surge" that happens each time an electric motor is turned on.  It actually saves you a significant amount over older style A/C systems, and perhaps if your A/C is getting a bit old, an inverter system should be on your list of things to do.
Here's a much less obvious source of poor energy efficiency with air conditioning systems - power wasters in your home that produce heat.  The refrigerator that you're also checking on the energy use of - it uses energy to remove the heat from your foodstuffs and pumps it into the air inside your house! Where your A/C has to process it a second time and cool the resulting hot air...
Less obvious sources of heat again are:  Cooking heat (is your range hood in good order, and does it move that heat outside not back into the house again?) and the heat from TVs, PCs, monitors, and other devices.  Best way is to feel above them with your hand - are they generating a steady warmth even when on standby? When operating?  
The best answer is to not leave such devices running, have a range hood over the cooking area, and if you have a refrigerator in an alcove, try and get some form of venting installed above it that takes the heat outside the house.
Two last things to consider when you're looking at your climate control bill - is there insulation in the ceiling and the walls, and is there a ventilator for the ceiling space?  These two things together can cut your climate bill by a quarter.
In part 3 I'll cover the other power wasters and how to deal with them.
(to be continued)


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