Saturday, October 15, 2011

Adventures in Electricity.

Our power bill was getting huge. We were paying $350/month, and that was in the summer. Winter bills would be considerably larger. It was well past time to do something about it.

First up, change electricity providers. In New Zealand, Consumer NZ researched all of the electricity providers and put up a web site, Powerswitch. Now, according to Powerswitch, I was with the most expensive power company (Contact Energy). So, I switched to Powershop. They weren't the cheapest, Meridian Energy is the cheapest, but Powershop had amazing reviews. I also wanted a smart meter so that I could easily track our usage, and Powershop makes them available.

So, I switched to Powershop. According to PowerSwitch, I would save $675 on a bill of $4066, or >15%!

Side comment: Make sure to provide a final reading to your provider. They have a habit of over estimating your power usage to keep your as a customer as long as they can - you pay the estimated final reading, not an actual reading.

In New Zealand, there are different ways of saving money when buying electricity. The first and easiest is to sign up for ripple control. When you sign up for this, in times of peak power demand, the power company will turn off your water heater. If you give them this ability, they will discount your power by ~10%. Sounds like a good idea, except for one problem - it doesn't work. I repeatedly had the ripple controller turn off the water heater and then fail to turn it back on. Nothing is more unpleasant than getting into the shower and there not being any hot water, calling a plumber, who tells you the problem is electrical, and then calling an electrician who tells you the problem is the lines company. TWICE.

When that happened, I turned off ripple control, and I will never turn it back on.

Powershop gives you a different way of saving money. They offer time of day charging. This provides a discount on electricity between the hours of 11PM and 7AM. It has the same effect as ripple control, only it's under my control instead of the lines company's.

With the Powershop "All Inclusive" plan, they currently charge 23.93c/kwh. This is for the ripple controlled power. Then there is uncontrolled at 26.23c/kwh, that's ~10% more.

However, if by switching to Day/Night Uncontrolled, I'm paying 24.07c/kwh day and 15.17c/kwh night. That means that as long as I shift a certain amount of power to the night, I end up saving, and don't need to keep ripple control. The magic ratio is:

23.93 = 24.07 * x + 15.17 * (1-x)
23.93 = 24.07x + 15.17 - 15.17x
8.76  = 8.9x
0.98  = x

That means that as long as I move at least 2% to my night plan, I'm better off. Seems strange, the service rep indicated that the magic number was 10%.

I switched plans, and installed a smart meter, which cost $165. The savings from 26c/kwh to 24c/kwh (the minimum savings), with an average usage of 1600kwh/month, I have a payback of:

2c/kwh * 1600kwh = $32/month
$160 / ($32/month) = 5 months.

five months! That's pretty kick-ass in anyone's book.

To recap:

  1. Shop around. You can save a tonne of money with another provider. Switching is free and easy, just head over to
  2. Change plans. Investigate day/night plans, particularly if no one's home during the day,
  3. We're at a savings of >25% from where we started, with more to come.

Saturday, September 03, 2011

Powersavings and water heater.

I have switched to Powershop, a New Zealand power company that provides intelligent meters with daily readings. This makes it really, really easy to see the impact of changes you make to your power usage. Not only that, but they provide time of day billing, where power from 7AM to 11PM is 50% more expensive than night time power.

That convinced me to look at how we used power. First, I shifted the laundry and dishwashing. I made it either the last thing I did before bed, or the first thing I did when I got up. That made a moderately substantial change in our bill, but nowhere near what I was hoping for. It was time to track down the big user in our power bill.

We are currently using about 40-50kwh of power per day. In New Zealand, we have expensive power prices ($0.25/kwh), so that's $10-$15 per day. Not cheap. The power meter we've got will tell us how much power we are currently using, which allowed me to zero in on the big users. First, just sitting there doing nothing, we use ~200w. That's for the server (with six HDs), networking and other vampires. Not bad, and not the main power user, they are constant background use, so they only end up being 5kwh/day. 10%, but not bad, bottom of the heap to fix. Next are the heat pumps and dehumidifiers. The dehumidifiers pull about 400w each, so they're a biggy if they were running all day. Heat pumps, also not a biggy, although they can pull about 5kw each. We're going to have to look at passive dehumidifing for the house if we keep it.

The biggest power user in the house is the hot water heater. It looks like it is using about 20kwh per day. However, we don't need a lot of hot water. We don't use it for laundry, the dishwasher uses cold water and our showers all center around 6-7AM.

I looked into ways to save power. The first and easiest is to turn off the hot water heater when you don't need it, so I did that. Our power usage collapsed. From 45kwh to 24kwh. That's a savings of $5/day. Not only that, but we had plenty of hot water for the rest of the day. If we were worried about running out of hot water, we could turn the water heater back on, and it would be at temperature within an hour.

However, there's a big scary monster out there in water heaters - Legionella. The bacteria loves warm, stagnant water between 20C and 45C. That means it loves electric hot water heaters. The recommendation is that water should reach your tap at at least 50C to prevent legionella from colonising the pipes and fixtures.

Oddly, it seems that legionella is found in 40% of electric water heaters, but the disease doesn't seem to be that prevalent (1 case per 100k population/year). It only appears to be a concern for people who are immune compromised. If it does take hold though, it is very dangerous if not caught quickly.

Because of that, we decided to turn the water heater back on during the day. I decided to attack the problem from another direction. Depending on how quickly the water heater loses heat, I can keep it above 50C while still saving on power. If the water heater doesn't drop below 45C during the day, it can be left off safely, bringing it back up to 60C at night, quickly killing off legionella and making use of night rates.

I will conduct some experiments to see:

  1. What the temperature of the water is in the heater.
  2. What temperature water is reaching the taps at.
  3. How quickly the temperature drops off.
  4. How quicly the heater drops into the danger zone.

Sunday, March 06, 2011

Map of Earthquake Prone Buildings in Wellington

On the weekend, I took the PDF that Hon. Peter Dunne (my local MP) provided of the earthquake prone buildings in Wellington New Zealand and put them onto a map.

I initially tried to use Google Docs to do this, because I thought it should be relatively easy to map data from a Google Spreadsheet. I thought that this would be an initial usage scenario. It seems that it isn't. So, instead I used BatchGeo. They have a pretty quick and easy service, complete with Geocoding.

Here is what their online tool created when I gave it the CSV file:

View Wellington NZ, EQP Buildings in a full screen map

The full screen map includes a list of the locations mapped.

Of course, the next morning, I found out that James over at maptd used Google Fusion Tables, which allow you to directly map data from a spreadsheet onto Google Maps. I'll have to look into them next. I would like to be able to keep the grouped view that BatchGeo provides in any reworking.