Energy Efficient, Solar Home for under $250,000

Holly and I have been keen to open our house for Sustainable House Day the last couple of years, but we’ve always had some excuses, a new baby, a lack of landscaping, too busy….. This year we bit the bullet and said yes. Our house in Torquay is a passive solar, solar powered energy efficient partly sustainable design. Four years ago we were first home buyers and we wanted to have a house that was comfortable, functional and cheap to run, but we, like many other first home buyers were on a budget. I wanted to be able to prove that it was possible to build an energy efficient home on a budget, and not have to make compromises on our lifestyle or comfort. After all the majority of Australian homes are not grand designed, architectural masterpieces. In the end our budget ran out around $230,000 for the house, although we have still a little work to do around the garden, we thought that this was pretty reasonable, and an achievable option for many Australians wanting to build a new home. I probably should give you the heads up now, that this is a longish article.

Solar House

We’ve been in the house now for a little over three years, there are always new things that we would like to do and there are some things that if I had my time again I would do differently, but on the whole we’re very happy with it. We were in the house for a few months’ pre-solar power system and pre-baby and our electricity consumption sat around 4kWhs/day (Kilowatt Hours). Since then we installed a 2.47kW solar system, which generates an average of 11kWh/day. Since we’ve had Ruby our consumption has gone up 1-2kWhs/day, mainly due to more washing and my wife, Holly, being home some days (doing more baking). So our current electricity consumption is about 5-6kWh day, 2kWh of which is being supplied from our 2.5kW solar system, the other 9kWh/day of solar energy that’s generated goes into the grid at 70 cents. Our electricity retailer has been depositing about $1500 a year into our bank account for the electricity we are exporting from the solar system. Any energy we purchase from the retailer is 100% Greenpower too, so although this doesn’t directly power our home it does go towards supporting renewable energy sources. We also have mains gas connected to our Solar Hot Water boost, cooktop and Rinnai Energysaver space heater. Our gas consumption varies quite a bit, from 5-25MJ/day (MegaJoules) during the spring, summer and autumn months through to 40-100MJ/day during winter (the 100MJ bill was the first winter with a newborn). Our bimonthly gas bills range from $30 in summer to $90 in winter.

We built our home through Pivot Homes in Geelong and I think in the end we got a 6.8 star rating for energy efficiency. Pivot were patient with us on the many sustainable design requests that we had and although some of these things were new concepts for them and we had to push them in some areas, we were very pleased with the final outcome. Our home is about 16 squares (150m2) plus the double garage, we found that looking at display homes and talking to a number of builders that the “McMansion” is alive and well in Australia and it was uncommon to find plans for houses under 20 squares. Sizing the house to our needs was important and by keeping a smaller floor space, it allowed us to spend money on other features. It’s basically a three bedroom home with one large open plan living and kitchen area on the north side, two bathrooms, a laundry and a double garage. I work from home and use one of the bedrooms as an office space. Now that Ruby is approaching 18 months, I’m being told that if we have another baby I might need to look for a new office, but at the moment space wise things are still good, the only thing we may be wishing in a few years is that we had built in a study, only time will tell.

Photovoltaic Solar Power System

Because I’m in the solar industry, and I am passionate about renewable energy, a photovoltaic (PV) solar system was always going to be a feature of the house. We installed a 2.47kW CIS (Copper, Indium, Selenium) thin film system, composed of 30 x 82.5W smaller than average modules on our north facing 20 degree pitched roof. The panels were manufactured by Japanese company Solar Frontier and our inverter is a Sunny Boy SB3800 from the trusted German manufacturer SMA. We got a pretty good price for a premium system at the time of about $9,000 (solar system costs have roughly halved since then) and we’re very happy with the system’s performance, pumping out an average of 10.86kWh/day at an efficiency of 4.397kWh/kW. The CIS panels have a special light soaking feature, where they are flash tested off the production line at 82.5W each, but once exposed to sunlight the actual power rating will increase, exceeding the panel’s badge plate rating. Even after nearly three years on the roof, our system on sunny days quite often produces over 3000W of power, I’ve even seen it up as high as 3300W, from a system rated at 2470W it is a great result. So the system is going great guns, but one thing I should mention is that things have changed a bit in the solar industry. The huge reductions seen in the price of crystalline modules over the last couple of years, in combination with the larger number of panels and surface area that thin film systems require mean that it is getting harder for some thin film technologies to compete. Extra costs for panels, racking, installation and fuses come into play. You can now install a larger crystalline system to improve your system’s output at a lower cost than going down the thin film path in most residential scenarios.

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Solar Hot Water

As well as installing a solar power system we also installed a gas boosted solar hot water system (SHW). We chose an evacuated tube system from AAE, 30 tubes tilted up to 60 degrees to optimise the system for winter sun; generally you will get plenty of heating in the summer months, but require boosting from the gas in the winter months. We went with a gas booster and a 315L stainless steel tank for longevity.

Passive Solar Principles

Passive solar design can play a huge role in the thermal performance of your home, orientation, window positioning, shading, ventilation, insulation and thermal mass all are important things to consider. Although our place isn’t perfect we think we got a few of these things right. I found that the website and Renew magazine from the Alternative Technology Association were both fantastic resources for doing research into what things we needed to consider as well as getting inspiration and ideas. We put our living area on the north side of the house and tried to include as many north facing, big double glazed windows as we could to let the winter sun in. We also included one meter eaves on the north side to block out the hot summer sun. This keeps the sun from coming in the windows or hitting our slab in the hottest summer months, but allows the low winter sun through to heat the home when it’s cooler. We also went with a concrete slab for the whole house to help include thermal mass in the design. The concrete is good because it is generally cooler than the air temperature in summer helping to cool the house, and warmer than the air temperature in winter (especially the polished parts exposed to direct sunlight) helping to heat the house. For the outside walls we opted for rendered foam cladding, which has a high insulation value; on top of this we used R2.5 insulation in the walls and R3.5 insulation in the ceiling. The insulation is great as it helps us to contain any heat in the house in the winter as well as insulate ourselves from the outside summer heat.

Heating & Cooling

We didn’t include an air conditioner in the house to begin with, because I expected that we wouldn’t need one, I’m also aware of the large cost that air conditioners place on the electricity grid by increasing peak demand on hot days, this is one of the reasons for much complained about increasing electricity bills. So far weave lasted two summers with minimal discomfort and I’m feeling vindicated. Temperature wise our home normally sits between 17-23 degrees with the highest and lowest temperatures I’ve seen registering at 27 and 14 degrees respectively. We only have one gas space heater in our living area; it’s not really used for eight months of the year, but takes the edge off the winter chill for us when needed, which is usually only winter mornings and evenings as the sun generally heats the house enough during the day. The space heater actually works well enough for us to provide some heat to the bedrooms before we go to bed by opening the hall door and letting the heat travel down the hall. There are also two ceiling fans in the living area and one in the main bedroom; these are helpful mainly on hot days to make us feel cooler.

The positioning of the double garage on the south-west corner of the house was done on purpose to help insulate us against the hot summer afternoon sun; there are also no windows on the west side of the house for the same reason. We do have some cross ventilation from north to south, which we sometimes use to flush out the heat on summer evenings, we just have to make sure the hallway door is chocked, because otherwise you will hear a big BANG as the wind slams the door shut.

Energy Efficient Appliances

Appliances were one of the other things that we had to consider and on moving into our new house we purchased a new fridge and washing machine. The Electrolux fridge was the most energy efficient one that I could find at the time, with an estimated usage of 349kWh/yr it is probably our largest electricity consumer in the house. Our Bosch washing machine was also selected with energy/water efficiency and longevity in mind. When picking lighting for the house I was on a mission not to include any dreaded halogen down lights in our home, a lot of houses that I’ve seen have over 30, 50W down lights installed, which as well as being inefficient, often comes with the added handicap of having square meters of uninsulated ceiling area for heat to escape. We went with good old baton holders and to begin with we opted for compact florescent lamps (CFL) for most of the fittings, however we did also install a few LED lights in the kitchen and bathrooms, which on the most part have been great, although one of them gives off a slightly yellow light. My aim would be to replace these all with LED’s as time goes on, recent technology improvements and price decreases have made this a much more viable option.

Edible Garden

The garden and landscaping has been a constant work in progress for us, sometimes I wish that we had just borrowed some extra money and finished it off to begin with. Before moving into this house I’d had limited experience and success with growing my own food, but food can be a large part of our environmental footprint that we leave on the planet and local food production, I believe, is an important part of the puzzle. We started out with four vege boxes which we rotate with different vegetables across the seasons. Although there have been times when our vege boxes have been neglected, we have had some wins. Tomatoes, strawberries, broad beans, snow peas, spring onions, potatoes, basil, parsley, kale, leeks, mint, oregano, rosemary, corn, chives, cucumbers, chillies, capsicum, eggplant, carrots, beetroot, spinach, lettuce, broccoli and pak-choy have all had a run in our vege boxes, some with more luck than others. An honorable mention goes to the zucchini plague of 2012, where we were inundated with zucchini’s for weeks on end, we couldn’t eat them quick enough or give them away fast enough, by the end of it Holly was sick of cooking them and wrote a great blog post called zucchinis 7 ways in 7 days, on some of the recipes we used.

Zucchini Plague

Along with the vege boxes, we’ve planted a few fruit trees, we had about 100 Gala apples off our dwarf apple tree this year and our lots o’ lemons tree is currently living up to its name, the lime and nectarine tree have been more reserved in their offerings and more recently I’ve purchased a blood orange, lemonade and mandarin, which upon writing are yet to go in the ground.

As far as dealing with food waste, we have got two worm farms going that eat up most of our vegetable scraps, turning them into rich usable compost for the garden. We’ve also experimented with a Bokashi bin, which allows you to include meat scraps for composting as well, but this is currently not in rotation due to us running out of the sprinkly stuff you put in it to help the bacteria “pickle” the contents. We have also installed a 5000 Litre water tank which helps us water the garden as well as supplying water for the toilet and laundry.

As I mentioned at the start there a few things that we would probably do differently next time and a number of things on the to-do list. Grey water is an area we have yet to delve into, chickens will still require a bit of convincing for my wife (although I think I’m nearly there). Wooden window and door frames next time, instead of aluminium due to the high conductivity of the aluminium, the double glazing is doing its job, but is being partly undermined by the heat let into the house through the frames in Summer, more LED lighting and more time in the garden are also on the list. One major thing that I feel was a mistake and I would change if I had my time again is the gas, I’m saying this because I’d like others to consider this when building. The heating itself and the costs are great, but on a larger level the idea that gas should be used as a transition fuel I think is flawed. I agree with Beyond Zero Emissions argument that we need to make a rapid move towards a renewable energy and energy efficient future by electrifying our buildings, and instead of wasting money on gas that will need to be transitioned away from at some time in the near future, we should be spending this on moving towards renewable energy sources to start with. If I had the choice I would put an energy efficient reverse cycle air conditioner in, to be used solely for heating.

I guess that covers a large part of what we’ve been trying to do around the house to live a more thoughtful and environmentally conscious life. The benefits have been great, reduced costs on our electricity, gas, water and food bills and an insight into living a less wasteful life a little closer to nature. Come along on Sustainable House Day, Sunday September 8th 2013 to check it out, the Surf Coast Energy Group and Geelong Sustainability Group have houses open across the greater Geelong region.


Aaron Lewtas


Green Energy Options