« | 2nd August 2019

Reduce Energy Bills in your home at the same time as reducing carbon emissions

By Marie Mattinson July 2019



One of my objectives as a Sustainable building designer is to stay abreast of rapidly changing sustainable technologies & practices so I can assist my clients to make informed decisions. I provide information on the most viable, low cost /high outcome options, that will reduce their use of energy & lower their carbon-footprint. Although the cheapest & easiest time to deliver energy performance of buildings is at the design & construction phase there are many ways to improve the efficiency of an existing building.

Let’s start where energy is typically used within a home as simplified in the graph below. Please note that the percentages will vary based on the climate zone that the home is located, the occupants behaviour, size of the home, if there is a swimming pool etc. It is intended to provide an overview of the breakdown of consumption to identify potential areas to target.

  1. Identify your current household consumption so that you can establish your baseline energy consumption. You can do this by referring to your past electricity & gas accounts. You can also purchase a wireless in house energy consumption display so that you can modify how you use appliances to see what impact that has in reducing your energy usage Choice.com have a review of different monitors available. Some solar PV companies provide a monitor as part of their system such as ‘Enlighten’ by Enphase. By adjusting your time of use to match when your solar PV system is producing, or if you don’t have solar, to the off peak period you can reduce your bills.
  2. Heating & Cooling– is the largest consumer of energy in our homes. Ways to reduce this are
  • Improving airtightness by sealing gaps & preventing transmission of warmed/cooled air between the inside & outside.
  • Restricting the heat transfer through windows, ducts, downlights etc A site inspection by a sustainable building designer may be required to identify ways to do this, eg. Is there a view that needs to be taken into account? Is it feasible to use landscaping, such as a deciduous tree outside a west facing window? Would an external screen be viable/beneficial?
  • Utilising an efficient heating & cooling strategy- eg solar PV panels & battery in conjunction with highly efficient electric heating such as airconditioning or if suitable underfloor hydronic heating. Please note that ducted reverse airconditioning loses efficiency through the ducting, therefore insulation of the ducting should be specified if this is the form of heating/cooling selected.
  • Improve insulation of walls, ceilings, floors & windows (Difficult to achieve without renovation)
  • Add some thermal mass to your home if you have the benefit of solar access & are doing renovations. You will need some professional advise by a building designer to do this, as other aspects have to be taken into consideration such as having the ability to release hot air on summer nights, being able to control sun access so that it is welcomed in winter but also blocked in the summer utilising cross ventilation etc.
  1. Water Heating
  • Reduce hot water use- ideas include installing water showerheads, reducing lengths of showers.
  • The most efficient & cost effective water heating currently is an electric heatpump in conjunction with solar PV.
  1. Appliances
  • Recycle old inefficient ‘drinks’ fridge.
  • When appliances need replacing, seek out most energy efficient option that is available.
  • Electric induction cooktops in conjunction with solar PV is the most efficient option currently. Sidenote- many expert cooks highly recommend cooking with them rather than gas.
  1. Lighting
  • Use reputable high-quality LED lighting, beware the poor-quality versions. Compare the light colour renditions, I personally use the warm white light as I find the cool white very stark.
  • Maximise natural light eg modify window coverings. Skylights should be considered carefully due to their potential to transmit unwanted heat in summer & lose warmth in winter, the trade off may not be worth it.
  • Paint interiors with lighter colours to reflect light.
  1. Install Solar Photovoltaic on your roof-
  • The payback period is approximately 5-7 years depending on your energy usage, the orientation of your roof & the size of the system. The solar installation companies will be able to give you an estimate of the power your system will generate, to assist you with this calculation. Even if you need to borrow the money for the system, with interest rates being so low it is a good return on investment.
  • Select the most efficient panel you can afford to minimise the area of roof required so more panels can be added later if you choose to.
  • Get a performance guarantee in writing.
  • If your roof is partially shaded at certain times or if your roof faces south consider buying panels with individual inverters per panel to improve efficiency. Such as the enphase system which we installed on our south facing roof. To follow is a screenshot of the overview page for the 1stof March As you can see in March more energy is being produced than we are using. In July it is the reverse. By installing a battery we can store the extra energy being produced & draw on it when it is needed but because the payback period currently is longer than the estimated lifespan of current batteries for now we have decided to set timers for appliances where feasible to operate whilst the panels are generating power, eg the pool pump & cleaner,  dishwasher etc. & the excess energy is sold back to the power retailer.


  • We used Solaray as an installer on our house & overall I was happy with their service. One word of warning is that I was told to arrange for my meter to be upgraded after the panels were installed. So after waiting the12 weeks to have my system installed, I was disappointed to find there was a further 3 months wait for my meter to be upgraded by energylocals.


  • Also to reduce our family & neighbours exposure to unnecessary radio frequency radiation, I requested that our meter be manually read quarterly rather than data being transmitted wirelessly.


  • Wiring to be appropriate for future installation of battery & electric vehicle charging point.


Above is a summary graph sourced from low carbon residential buildings-retrofit-apo.org which indicates the different aspects of retrofit options.

I hope this information is helpful to you, If however, Zero energy consumption or Zero carbon is your goal, I can assist you by utilising the appropriate design methodology, design & detail a high-performance building  to ‘Passive House’ or ‘solar passive design’ standard. If you need any further guidance please contact me 0410 191908 or email me at marie@mattinsondesignstudio.com.au



0410 191 908
Email: marie@mattinsondesignstudio.com.au