Monday, July 25, 2011

Mercury's 62 things that use power

Dear Reader,

Yes, Mercury has issued a - possibly - quite helpful list of 62 things in the home, and how much power you'd expect them to use per hour. Well, how much they'd cost to run per hour.

A couple of assumptions that you need to be wary of, though, is that they assume you've got a rate of 20.14 cents per kWh, and that you're running your appliances constantly.

I find it strange, however, that they haven't included the cost of running the hot water cylinder, since they've pretty much got everything else (even what's in the kitchen sink!).

So I'll show you how you can work out what your hot water cylinder should be using. First of all, we need the 'water heating calculation', which is:

(3.966 x (number of litres of water that needs heating) x (difference between start and end temperatures)) / 3.41

This will give us the number of watts we'll need to be able to heat the specified amount of water in one hour.
To find out how many hours it will take if we have a limited number of watts available, we divide the number of watts we'll need by the limited number of watts.

O.K., let's get into the examples:

Let's say you need to heat 135 litres to 65 degrees from 10 degrees, and that you have a 3,000 watt element to do it with. By the way, this is pretty much the standard set-up of residential hot water cylinders.
Anyway, let's plug these figures into our equation:

(3.966 x 135 x 55) / 3.41 = 8,635.645 watts needed to heat that amount of water in one hour.
But since we only have 3,000 watts, it'll take 2.879 hours, since:

8,635.645 / 3,000 = 2.879 hours

So, how much will it cost? Taking the amount Mercury gives us, we'll turn it into a dollar amount, and multiply it with the number of hours taken:

2.879 x 0.2014 = 58 cents every day - assuming the hot water cylinder only needs to be heated once (and it might just need to be heated once, depending on how much hot water gets used).

To find out what you should be paying to run your hot water cylinder, find out what size the element is, how many litres it holds, and what the temperature is at the cold water tap (if you're having a bit of trouble, contact us on 0800 72 83 44). Then multiply it with the rate you're getting for the hot water cylinder (which is probably on a controlled rate, i.e., you're paying less for it); you'll probably quite surprised.

Thursday, July 21, 2011

Geothermal Heatpumps

My dear reader,

You've read right: if you live on the edge of a thermal vent - or a volcano - you can now get heat-pumps that shift that warm, warm geothermic air straight to the inside of your house (absent offensive gasses)!

No, not really: 'geothermal' is a bit of a misnomer; what the 'geothermal' heat-pump does is move heat from below the ground to the inside of your house.

So, how's this different to the average heat-pump? Well, not by much, really: heat-pumps 'shift' heat from the outside to the inside of the house (or from the inside to the outside), which allows them to be really efficient since they have the effect of generating more energy than what they use up.
This, of course, relies on it not becoming too cold (since the absence of outside heat would make it harder to shift it inside).
The good thing about shifting heat from the ground is that the ground tends to stay a pretty even temperature (15 degrees, according to the link at the end of the paragraph), so the 'geothermal' heat-pump wouldn't be affected by sudden shifts in air temperature. You can find out about it here.

Question: how much will it cost?
Answer: around $42,000 (excluding GST), based on their estimates. However, they reckon that the running cost is about $400 per year, which amounts to an average of $33 per month. So, if the Energywise website is anything to go by, we would spend an average of $58 per month, if we had a power bill of $200 per month.
This would amount to savings of $25 per month; so, if we were going on the amount saved alone, it would take 140 years to pay for itself.

140 years! Better to go on other factors, like what heats the best, and what has a longer lifetime, methinks.

Any words of caution? Yes: this stuff could be seriously damaged in an earthquake; but, then again, what wouldn't? Make sure you talk to your insurers to see what they're offering in regards to that.

Tuesday, July 19, 2011

Return of the Power Pand blog

Dear All,

Sincerest apologies for the distinct lack of updates, but that'll change from today onward.

Now, for the news:

The latest campaign to find out 'your number' may well be worth checking out. A word of caution though: make sure you take all the factors into consideration!

For instance, would you get cheaper power all year round? Do they factor line charges into the rates? Do they factor GST into the rates?
You see, it may seem as if they give you cheaper rates, but there may be things like line charges and GST that just get added on top; and this may result in a larger overall bill. Buyer beware!

The Connector blog over at gives a bit of information on a couple that built a wind turbine to power their home, and are returning power to the grid. Now it's good to be able to generate your own electricity, but charging the transmission people for it is even better!
So how much do they get paid? Around $300 every month.
But before everyone hails this as the next great step in power savings, have a look at how much they spent: about $31,000!
Ignoring the costs of maintenance, it would take about 8-and-a-half years for it to pay for itself, and this doesn't include any interest they might need to pay back if they took a loan. And imagine trying to get consent for a turbine on top of a 10-metre pole!

But, if they're making good savings, all power to them!