Thursday, July 03, 2008

Getting A Handle On Electrical Use

We've been looking into solar electric power for our home.

As a part of the planning process, I've been trying to get a handle on our electrical usage and find ways to lower it. Reducing consumption has a huge impact on the cost of going solar. So far, we have gone from using 360 kWh in January down to 250 Kwh in June. My goal is an average consumption of 200 kWh per month. This will save us hundreds of thousands of yen (thousands of dollars) in the capital cost of the solar PV system.

Admittedly, part of the lower consumption during that time has to do with longer daylight hours, so isn't really long term savings, but most has been achieved by simply turning things off or unplugging them when they are not in use and changing out the two incandescent light bulbs we had in the house for compact fluorescents.

To make it easier, I've purchased rocker switches that plug into wall outlets and some power strips with individual switches as well. Computers, speakers, the ADSL modem and wireless router all have "wall wart" transformers that suck up energy and even if each is a small amount for each, taken together it is significant. Those, plus the TV, stereo, and DVD player can also be draining your wallet even when they are "off", so best to turn them off at the wall outlet. The new switches make it easy to shut everything down when we leave the house or before retiring for the night.

I've also adjusted the number of fluorescent tubes in our kitchen fixture which is the one that gets the most use. It has five 15-watt tubes and a switch to select either 3 or 5 tubes. We almost never use 5 and even 3 seemed brighter than necessary to me, so I removed the center tube. Now we can select 2 or 4 (30 watts or 60). May not seem like a lot, but it adds up over time. My SO didn't even notice a difference until I pointed it out a week later.

It is also helpful to see how much each electrical item uses on average. One way of course is to look at the label, but that does tell the whole story. For example, our refrigerator is rated at 123 watts and estimated to use 460 kWh per year. But such ratings can vary depending on many factors. Is the kitchen heated? If so, that will increase the work load on the refrigerator. Are the temperature settings for the refrigerator and freezer set properly? Do you keep it at least 75% full? (A full refrigerator stays cool more easily). Do you open the door a lot? Do you keep the coils clean? And so on.

I wanted to know how much electricity OUR refrigerator, the way WE used it, was consuming. To get that answer, I picked up the following gadget:

It is called "ecowatt model T3T-R1" and is basically a watt meter. It plugs into an outlet and then you plug the item to be measured into a receptacle at the bottom of it. I paid about $22 for it.

This model has a digital display that sequentially shows how long it has been plugged in, how many watts have been used, how much CO2 that represents if the power is coming from fossil fuels, how much the power is costing in yen (based on the current rate of 22 yen per kWh).

By learning where your electricity is going, you can adjust your use patterns and improve your home's efficiency.

For the refrigerator, I left the ecowatt plugged in for 3 days to get a good average (87.1 hours actually). The result: In 87.1 hours, it used 6.92 kWh, caused 3.82 kg of CO2 to be released, and cost us 152 yen. From that it is easy to calculate an average hourly rate of 79.5 watts, 57.2 kWh monthly, and 696 kWh per year (and CO2 emissions of 384 kg). Uh-oh! What happened to the manufacturer's estimated 460 kWh per year on the label? Glad I checked.

For you North American readers, there is a similar tool called "Kill A Watt" which actually has some features I like better than those of the ecowatt. Their basic model sells for about $20. You can check that out here: P3 Kill A Watt
I've learned that my refrigerator uses more electricity than I thought and represents 23% of my electric bill. I will be more mindful keeping things off the top of the refrigerator, not opening the door as often or for as long, and not staying in the kitchen with a heater on during winter months.

Next month we are getting a new refrigerator and I hope it will deliver on its efficiency promises - it is larger, but is supposed to use less electricity. It may well do so, since the new one is better insulated and has a lot more drawers and compartments within it, which means that all the cold air doesn't flow out every time the door is opened. We'll see.

Hmmm...I wonder what the microwave is costing us?


tornadoes28 said...

Did you read my blog post about Japanese toilets and energy use?

Here is the link

Pandabonium said...

Thanks tornaodes28. Good post. Our toilet seat was the first thing I thought of as an energy waster. It was using something like 80 watts 24/7.

Rather than buy a "smart" one, I put a switch at the plug. Now it is off when not in use (it takes less than a minute to warm up when needed).

One thing being overlooked is that one reason they are popular here is that houses in Japan do not have central heat. My local weather is no colder than Los Angeles (I grew up there), but most LA homes have central gas heating. In Japan, a small heater is used only in the room being occupied and turned off at bed time. Bathrooms (water closets) are never heated.

So while the toilet seat wastes energy if left on, I think central heating as practiced in the US is much more so.

Martin J Frid said...

I have been curious about how my electric fan compares to the A/C. Does it make a huge difference to turn off the A/C and use a fan instead? My A/C is brand new (2007 model) so I'm assuming it is rather "eco".

The A/C has many different settings providing all kinds of choices, such as "soft" and "dash" (a quicker burst of cool air) which makes it even more complex to figure out how energy efficient it is.

Martin J Frid said...

Houses are not very efficient anywhere. In the US and Canada, only about 12% of new homes qualified for the Energy Star rating in 2007.

Not sure if other countries even try.

Pandabonium said...

I could be wrong (my wife often says I am) but it seems to me that an A/C has to use more energy. In addition to circulating air like a fan, it has to run a compressor motor to compress the coolant which intuitively means more total work.

Of course a fan does not lower the room temperature. In fact, it adds a small amount of heat and any cooling comes from evaporation of sweat and possibly drawing cooler air from another area into the room. An A/C cools the room (removes some heat), but sends the heat outdoors, adding to the air temperature of the neighborhood.

As for Energy Star ratings....
people are spoiled by cheap oil. (Even at $150 a barrel, oil is cheap for what it does.) They continue to heat (or air condition) their entire house to a comfy shirt sleeve environment, then cry about huge the energy bills. And they continue to move to places like Las Vegas, Nevada and Phoenix, Arizona which are literally uninhabitable without huge energy and water inputs that may not be there in the not too distant future - Energy Stars or no.

This is a tie said...

Seems like there have been a bunch of Kill-a-watt like devices popping up around these days! Not sure if they are better or worse but it is cool to see these coming around!