Household Energy Monitors

25 Nov 2010: The installations are very nearly all done.  Thanks for everyone's patience, it certainly took a lot longer than expected.  Thankfully, everything else has gone fairly smoothly.  Now that people have them in and are using them, I have started a Frequently Asked Questions page.  If you have any questions, I will do my best to help you out.  Email
Thanks for all the interest - we've had heaps!  This week (2-8 Aug) we'll go through the registrations and choose the short-list of 50, then get in contact with everyone. 
If you missed out on registering, stay tuned!  Hopefully we will run another bulk purchase later in the year, or early next year.

The South Hobart Sustainable Community is organising a bulk purchase of Household Energy Monitors.  This was be launched at the Home Energy Advice evening on Mon 21 June.  We are very pleased the recognise the assistance of the Tasmanian Climate Change Office via an Earn Your Stars micro-grant.

For a quick two-page summary of the bulk purchase, have a look at our flyer (400kb PDF).  Keep reading for more information and answers to common questions.

What is a Household Energy Monitor (HEM)?

An HEM is a device that measures the total amount of electricity being used within a house at any given instant.  A display shows the residents how much electricity is being used, at what cost, and also stores a history of electricity use.  This alows the residents to understand exactly what is using electricity from moment-to-moment, and day-to-day.  Armed with this information, they can eliminate standby power and change their behaviour in order to save 10-20% off their electricity bills.  This saves money, and reduces greenhouse emissions!

How does it work?

A sensor is clamped around the wires entering your house from the electricity meter.  This sensor detects how much electricity is running along the wires.  It transmits that data wirelessly to the display, which you can put wherever you like in your house (note that the display must be within 25 metres of the meterbox to pick up the signal).  This is updated every few seconds, and recorded in the memory of the unit.  You can view how much electricity is being used at that moment.  When you turn on or off lights or applicances, the display will change, showing you how power hungry (or not) they are. You can also connect the unit to your computer with a special USB cable and download the historical data.  This can be viewed in pretty graphs with various software that is available.  You can even upload it to Google PowerMeter.

How much can I save?

How much electricity you save depends on how much effort you put in to eliminating wasteful electricity usage.  The following table gives you an idea of how much the average household would save for differing levels of effort.
 Easy        Medium  Vigilant

  Average  -10%      -20%  -30%
 Cost $1575  -$157.50
 Energy 10000 kWh  -1000 kWh  -2000 kWh  -3000 kWh
 CO2   2300 kg  -230 kg  -460 kg
 -690 kg
The above figures are based on an average Tasmanian household using 50% for light and power and 50% for heating.  Fixed costs are not included.

How much does an HEM cost?

It depends on your meter box and how you are billed.  The simplest install will cost $115, which includes free installation.  Additional costs will be incurred if you have more than one tariff, three-phase power, solar panels, or want a USB cable to download the data to your computer.
 Item  $
monitor  115
USB cable
additional clamp
additional transmitter

A guide to typical setups:
: This is the simplest installation.  Price is $115, or $130 with USB cable.
Light and Power tariff only: This is also straightforward. Price is $115, or $130 with USB cable.
Light and Power and HydroHeat tariffs: The extra tariff necessitates an extra clamp be installed in the meter box.  Price is $135, or $150 with USB cable.
Three-phase power: This requires two extra clamps.  Price is $155, or $170 with USB cable.
Solar power: this requires an extra transmitter so that the solar power can be measured separately to the main power.  Cost is $165, or $180 with USB cable.

That seems awfully complicated!

Yes!  When you register to participate in the bulk purchase, you will need to answer some questions so we can work out exactly what parts to order for you, and how much it will cost.  Isn't it nice that we have done all this hard work for you?!

How long until I recoup the cost of the HEM?

Well, if is costs you about $150, and you make use of it to reduce your electricity usage, then you can expect to make that back within the first year, or even faster!  After that, everything you save is a bonus.  And given that electricity prices seem to be headed inexorably upwards, then the savings grow greater every year. An HEM is one of the easiest ways to reduce the impact of your electricity usage on the plant and your bank balance.

Why is installation free?

We have kindly ben given an Earn Your Stars grant by the Tasmanian Climate Change Office.  We are using this grant to cover the cost of paying an electrician for the installations.

What HEM will you install and why did you choose it?

We have chosen the Current Cost ENVI.  There are a range of different HEM's available.  They can be separated into two categories: quite basic ones that cannot record historical usage, and more sophisticated ones that have a history and provide some sort of interface with a computer.  The former include the well-known Cent-a-meter and what you might pick up from Bunnings or Aldi.  With unusual meterbox arrangements, these may be impossible to install.  The more spohisticated options include the ENVI, the WattsOn, the efergy e2, and the WattsClever.

The unique advantages that swung us in favour of the Current Cost ENVI were:
  • a very attractive bulk purchase price
  • flexibility to fit a range of situations
  • support for Google PowerMeter
  • no batteries needed for the display, and battery life of 7 years in the transmitters

How much does the bulk purchase save me?

Lets consider a typical installation in a house with two tariffs (Light and Power, and HydroHeat).  With a USB cable, we will charge you $150.  The retail price is about $175, plus you might have to pay for shipping (say $10+), and then you will have to get an electrician to install it, which could cost $50 or more.  That brings the price up to at least $235.  So we're saving you a good $85, not to mention taking away to hassle of having to choose a unit, get your head around the complexities and deal with an electrician.

Can't I install it myself?

No.  Because installation requires messing around inside the meter box, it must be performed by a qualified electrician.

How do I sign up?

Sorry, registrations have closed.  Registrations close 26 July 2010.  By registering you are making a commitment to pay for an HEM.  You also agree to participate in a simple survey so we can get some feedback on how smoothly things went, how happy you are with the HEM etc. 

I don't live in South Hobart, can I participate?

Maybe.  We will give preference to people within South Hobart, and then those that live in the surrounding areas.  So sign up in case we don't get sufficient interest from within South Hobart.

How many HEMs are you going to purchase/install?

50.  In order to limit the scope of this, we don't want to do more than that at a time.  If more than 50 people sign up, then preference will be given to those who got in earliest, and to South Hobartians.  If we get heaps of interest, then we will know that there is lots of demand and are more likely to do it again in the future.

How do I pay?

We will send you an invoice after you have registered and we are happy that we have all the information encessary to proceed.  We will only accept payment via direct credit to the SHSC bank account (details will be on the invoice).  Invoices must be paid by 26 July 2010.

When will the installation take place?

If all goes well, sometime in August.  If not, then sometime later, but we hope before the end of the year!  We will keep everyone informed via email.

You haven't answered my question!  Or I have some other problem!

Email us at hem.bulk.purchase <at>

Subpages (2): FAQ Registration
Garth Coghlan,
17 Jun 2010, 23:42