Money-saving results in Melbourne This family of four saved around $250 last winter by heating their home with a reverse-cycle unit instead of their older gas ducted system. An extract from an article by Stephen Zuluaga, in ATA‘s ReNew magazine edition 140 reproduced with permission from the ATA.
IN 2012, our family moved to a three bedroom brick veneer townhouse in the south-eastern suburbs of Melbourne. The house was constructed in 2001 and it’s likely that’s when its original gas ducted heating, water heater and stove were installed. We’d always been interested in keeping our energy costs down, but, like many people, we just assumed that high gas bills in winter were a part of life. We found that our two-month gas bill spiked significantly in winter due to heating, rising from around $80 in summer up to around $400 in winter.
Then in September 2015 I came across an article on The Conversation which proved to be a turning point. Tim Forcey’s article described research undertaken at the Melbourne Energy Institute which suggested that efficient electric appliances—heat pumps—could heat your home more cheaply than gas.
Intrigued, I got in contact with Tim to learn more. He introduced me to the My Efficient Electric Home Facebook group and, through contacts made there, I spoke to many efficiency experts and interested householders like myself about ways to reduce costs and increase efficiency. In hindsight I can see that I was heading down the path of all-electric, but I wasn’t really looking at it like that at the time: it was just about replacing inefficient appliances with efficient ones.
There are many motives for wanting to improve efficiency and for us the primary driver was financial. Over the course of converting our house to all-electric, I spoke to others who had a combination of environmental, efficiency, financial and technological motives. I really like the fact that no matter what your motive is, you can get an outcome that both lowers costs and reduces environmental impact.
Our house was like so many others
Our gas-fired ducted heating system used underfloor ducting and did an okay job. On many occasions we’d notice parts of the timber floor were warm, suggesting the floor had poor insulation or the ducting was split. Apart from this, the heater had pretty even heat distribution. Beyond running costs, we didn’t have any major problems with it at the time we decided to decommission it.
In May 2016, winter was coming and so was our second baby. This meant the likelihood of regular 24/7 heating, bringing with it the threat of huge bills from our gas ducted heating system. So we decided to focus on installing reverse-cycle heating first (on the journey to all-electric).
We also decided that if we were going to make capital investments we would aim to get really good operating expense outcomes. Thus, we went for a higher cost but higher efficiency unit—the 3.5 kW Daikin US7 reverse-cycle unit.
We spent a bit of time planning the unit’s location and sizing to ensure a good result. My wife Stacey is much less tolerant of the cold than I am and she’s happy with the heating setup we have now. (However, no amount of high efficiency heating is going to help us negotiate the temperature setting!).
In many cases people will need to buy two or more reverse-cycle units due to house layout and size. Luckily for us, our house layout means we can heat the whole house with a single reverse-cycle unit without compromising thermal comfort.
I really like the way the reverse-cycle unit gradually powers up and down as needed, compared to our on/off gas furnace. We find this keeps temperature levels more consistent and means it rarely runs at full power, except on really cold nights or when first turned on. The living area is the first to heat up which usually takes about 10 minutes from a cold house. Warm air also gets thrown down the corridor to our bedrooms where heating is less critical. This layout results in the living area being about 2 °C to 3 °C warmer than the bedrooms, depending on how cold it is outside.
We had to tune the unit’s settings to get this whole-of-house outcome. The most important changes were turning the fan speed up to the highest and pointing the louvres at the wall opposite. Despite that, the unit only runs the fan at top speed if it’s heating at full power and we find it’s reasonably quiet anyway.
On the coldest of winter days, the unit might take up to two hours to heat the whole house to the desired temperature, but we can set a schedule so that it comes on in advance of when it’s needed. It’s also controllable via the internet—so if plans change we can alter the settings remotely.
[Ed note: if you have solar PV, you can program a heat pump for hot water or heating and cooling, to run during the day to use the solar power and the warmer daytime temperatures to potentially run more cheaply.]
Consider the whole building
There is no point saving on input energy for heating and cooling if it’s only to float away through poor door sealing or leaky vents. Thus, we have continued to make changes to the building envelope to improve efficiency. We have a roof-mounted evaporative cooler which we still use as it’s cheaper to run than refrigerative cooling. During winter I fit foam behind the closed louvres in the ceiling vents. This is the cheap expansion foam used in concreting; $12 gave me double what I needed. We have double-sided foil insulation in the roof cavity attached to the underside of the rafters, mainly to reject heat from hot tiles in the summer, but this also yields some warmth retention in winter.
All our external windows and doors are draught sealed and we don’t heat rooms like the laundry at all. In our living room, we have two sets of large 2.5 m-wide curtains and on top of them is a long sheet of acrylic sheet (perspex) to act as a hidden pelmet. This helps stop the warm air slipping down between the curtains and windows and being cooled.
Sharing some of my lessons
If I was asked about what I’d say to someone who is considering changing out their gas appliances, I’d say “do it.” Of course you’ll have to decide how far through their life your gas appliances are, but you can expect to save money on running costs when you do change. It cost us $7800 to purchase and install our new heater. Plan it properly and make sure the people you’re dealing with really understand how to achieve the best results as our suppliers did. My most important lesson from this would be to make sure you’re working with experts on energy efficiency—just because someone has put in lots of air conditioners or water heaters does not mean they are knowledgeable about energy efficiency.
Stephen is a co-founder of training business Peer Camp and a teacher at RMIT, with a strong interest in technology and energy efficiency.