If you're building a new home, you have a once-only chance to lock in low running costs for decades. Electric cars get the headlines, but I'd put your money into the house first. How you build and power your home has a bigger and more certain payback than what's parked in the garage.
The order I recommend:
- Use less energy (insulation, airtightness, design).
- Make your own (solar).
- Store it (battery).
- Then think about the EV, charged from your own roof.
Why the EV comes later
I'm not against electric cars. But they're not the first priority when you're building.
- Manufacturing has a footprint. Building an EV and its battery creates more emissions than building a petrol car. Life-cycle studies generally find that's paid back within a few years of typical driving, faster on a cleaner grid. Charged from coal-heavy grid power, the benefit shrinks. Charged from your own solar, it grows.
- Weight and infrastructure. EVs are heavier than comparable petrol cars, and public charging networks take energy and resources to build.
- Battery recycling. Recycling is improving, but it's still complex and energy-intensive.
- The house is a sure thing. Every kilowatt-hour your home doesn't need saves you money every day for as long as you live there.
The goal is to use less energy overall, not just switch where it comes from.
Start with the building
Insulate well
Insulate the ceiling, walls and any exposed floors. Your NatHERS assessment sets the minimum R-values for your home to reach the 7-star standard now required for most new homes. Going higher in the ceiling is usually one of the cheapest upgrades you can make.
Glasswool, rockwool or polyester batts sit between the studs. Adding a continuous insulation layer between the frame and the cladding reduces thermal bridging, which is heat travelling through the timber or steel studs themselves.
Seal air leaks
An airtight home has to be designed and built that way. It isn't an afterthought.
- Tape and seal window and door frames to the wall wrap.
- Seal the bottom plate to the slab and the cladding junctions.
- Seal every pipe, cable and duct that goes through the wall or ceiling.
- Use good weather seals on external doors.
Less leakage means lower bills, fewer draughts and better control over indoor air.
Ventilate properly
An airtight home needs controlled fresh air. A heat recovery ventilation system (HRV or ERV) continuously swaps stale indoor air for fresh outdoor air, passing it through a heat exchanger so you keep most of the heating or cooling you've paid for. An ERV also moves some moisture, which helps in humid climates. More on this in 12 benefits of installing a ventilation system in your new home.
Better windows
Double glazing reduces heat moving through the glass itself. Draughts are stopped by the frame seals and how well the window is installed, so you need both.
Efficient hot water
A heat pump or solar hot water system uses a fraction of the energy of a standard electric storage unit. Pair a heat pump with solar and set it to run during the day.
Then add solar and a battery
Size solar to your use and your network
Size your system to your actual usage and your network's limits, not a big round number. Many Queensland homes on single-phase power are limited to about 10kW of inverter capacity, with lower limits on how much you can export. Check the current Energex or Ergon rules with your installer before you buy panels.
Solar cuts your daytime power costs and reduces how much coal-fired electricity you draw from the grid. It won't take you off the grid on its own.
Add a battery
A battery stores your excess solar for the evening, when power is most expensive. With the right setup it can also keep critical circuits running during a blackout. Federal battery discounts have made them more affordable, so check what's currently available.
Plan the switchboard now
Even if you add them later, ask your electrician to allow space and cabling for solar, a battery and an EV charger. Running cables before the plaster goes on costs a fraction of retrofitting.
Water: tanks and on-site treatment
Rainwater tanks
A rainwater tank lets you water the garden and wash the car without using mains water. Rainwater is better for your plants too. For most homes, 10,000 to 20,000 litres is a good starting point if you have the space.
Sewage treatment
In Queensland you generally must connect to the sewer where it's available. On-site systems, such as aerated wastewater treatment systems, are for unsewered lots. They need council approval and regular servicing by a licensed technician, and treated water can be used on gardens within the approval conditions. Be careful what goes down the drain, because harsh chemicals upset the treatment process.
What to ask your builder for
- A NatHERS rating above the 7-star minimum, with the certificate.
- Higher ceiling and wall insulation than the minimum.
- A sealed, airtight envelope, with details on how they'll achieve it.
- WERS-rated windows suited to your orientation.
- A heat pump or solar hot water system.
- Solar sized to your usage and network limits.
- Battery-ready and EV-ready switchboard and cabling.
- A rainwater tank for outdoor use.
The EV can wait
Build the efficient home first. Once it's making its own power, an EV charged from your roof makes far more sense, both for your wallet and the planet. Using less, rather than needing more, is the real key to sustainability, and it starts with how you build.
Further reading
Decoding Home Energy Star Ratings: What Homeowners Should KnowUnderstanding the energy efficiency of your home is crucial. The NatHERS star rating, ranging from 0-10 stars, evaluates the thermal comfort of a house. A higher rating indicates better energy efficiency, potentially reducing the need for artificial heating or cooling.
Mastering Energy Efficiency: Air Sealing & Insulation TipsBuilding an energy-efficient home is more than just a trend; it’s a responsibility. Dive into the intricacies of air sealing, insulation, and the importance of thermal mass. Discover how these elements can drastically reduce energy consumption and promote sustainability.
Why New Homes Lack Energy Efficiency: Time for AccountabilityDespite the advancements in building science, many new homes remain energy sieves. Why? The focus of most project builders is on profits rather than energy efficiency. As homeowners pay top dollar for new homes, they later find themselves burdened with high energy costs.
Architects’ Role in Energy Savings: Building SustainabilityLearn about the crucial role of architects in creating energy-efficient homes. This article emphasises the impact of design choices on household energy use and the responsibility of architects to prioritise sustainability, offering strategies for reducing carbon footprints and energy costs.
