Friday, September 30, 2011

How to Save Power at Home, Part 1

Dear Reader,

A great many apologies for not posting last week; I'll try to be a bit more on-the-ball.
Now I'm sure you've noticed that I've been telling you quite a bit about new technologies that might hit our shores... a long time from now. Which is interesting and all, but not overly practical. So, I'd like to give you a bit more down-to-earth information, particularly on ways to save power.

Now, some of things I'm going to cover in the next few weeks you're probably already doing; but you probably don't have much of an indication of exactly how much you could save if you were doing them, and whether it was worth making the changes to get the savings (if changes needed to be made).

But, before I can get into all that, I need to show you what assumptions I'm making:

1. The power bill is $250 (if your bill is smaller, find out how much smaller by percentage, and apply that percentage to the amounts I work out).

2. You're being charged a flat-rate of 20 cents per kilowatt-hour (kWh); I'll write cent amounts in dollars from now one, i.e., 20 cents is $0.20.

3. The bill spans for 30 days.

4. Water flows out of the tap at 10 litres per minute (don't worry: this'll be relevant later).

5. Water flows out of the shower-head at 14.5 litres per minute (also relevant, but later).

6. Hot water heating accounts for 30% of the bill (based on what the EECA Energywise website says).

7. Space heating (heating done to heat rooms) accounts for 29% of the bill (see the Energywise website).

8. Lighting accounts for 8% of the bill (Energywise again).

OK, now that we have a groundwork done, let's have a look at lights.

I'm pretty sure you've guessed that I'm going to tell you to change to those cork-screw compact fluorescent lights - and I am.

But you might not know why, in the first place, the old incandescent light bulbs use so much power; well, around 98% of the power they use is actually converted into heat!
This is because they have to run electricity through a very thin bit of wire that has to heat up until it's white hot. And, it takes a lot of power to become white hot (go figure, eh?).

So, how much would you save?

75% on the lighting costs, and about 6% on the overall bill.

The reason for this is because the fluorescent light bulbs use about a quarter of the power used by the incandescent light bulbs.
Here are the sums:

15 x 60W incandescent light bulbs x 4 hours on a day x 0.2 x 30 = $21.60 every month
15 x 15W fluorescent light bulbs x 4 hours a day x 0.2 x 30 = $5.40 every month
And to work out the savings we go: 21.6 - 5.4 = $16.20
And to work out the difference it makes to the overall bill: (16.20 / 250) x 100 = 6%

OK, 6% isn't huge, but they'd pay for themselves in 4 months, since:
(15 x 8.99 (the cost of a 2 pack)) / 2 (since they come in a 2 pack) = $67.43
And to work out how long it'd take, we divide the cost by the savings: 67.43 / 16.20 = 4.14 months.

4 months for it to pay for itself? I'd say that's pretty good.

Next time, I'll have a look at why the fluorescents give off a funny light, and what you can do about that. And I'll have a look dangers they could pose with the mercury they use.

Yours sincerely,

Andrew Greaves

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