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What does it mean to use energy sustainably?
Three things: Energy Economy, Energy Efficiency, and Energy Flexibility.
Sustainable energy use is multifaceted. But it's also simple. The three principles of sustainable energy use are:
- Economy
- Efficiency, and
- Flexibility.
Economy is about using as little energy as necessary. Efficiency is about getting more benefit from less energy. Flexibility is about using energy when it is cleanest.
Economy is largely achieved through building science. Efficiency is largely achieved through electrification. Flexibility is largely achieved by time-shifting electrical demand—invariably towards the daytime.
Building science is key to energy economy because good building design and high quality materials will significantly reduce the amount of energy that you require. Electrification is key to energy efficiency because electrical appliances and vehicles are significantly better at turning energy into outcomes (e.g. comfort and movement) than combustion devices are (e.g. gas hot water systems, wood fire places, and petrol cars). Time-shifting is key to energy flexibility because our electricity grid is not always powered by the same mix of generators, so your energy use will be more sustainable if you match it to when clean electricity generation is most abundant.
There are exceptions and nuances to all of the above of course, but that’s it in a nutshell.
What's the fastest and cheapest way to use energy sustainably?
To start using energy more sustainably, first focus your attention on heating and cooling both air and water. These tend to be the greatest energy demands in a home. It's reasonable to suggest that these two tasks require ~80% of the energy used within the typical home. Other major energy loads include water pumping (e.g. pool pumps and garden irrigation) and transport (e.g. personal motor vehicles).
How to start? Reach for the low hanging fruit.
Typically the cheapest and fastest way to make a home more economical is to make it airtight. Then you won't need to heat or cool as much air. To do this simply 'draught proof' your home by blocking and sealing holes in the building envelope (e.g. ducts and vents, gaps around doors and windows, and loosely installed lights and electrical cabling). Having done that, go one step further and don't let your air lose its heat to the outside environment by coming into contact with intermediate materials that can act as 'thermal bridges.' Take some simple measures like installing high quality blinds (e.g. honeycomb blinds) and fit them tightly around windows so that air won't pass around and behind them. Also, consider using building materials that slowly absorb, store, and release heat. Such materials are referred to as 'thermal mass' and when that mass also demonstrates 'thermal lag' it will slow the rate at which your home's temperature changes, avoiding the need for active heating and cooling measures. Water, concrete, and stone are good examples of materials that add thermal mass.
Typically the fastest way to get a home to use energy more efficiently is to install electric 'heat pumps' to heat and cool your air and water. While ordinary heaters could only ever be as much as 100% efficient (yet never are) heat pumps can easily be ~400% efficient. This is because heat pumps are a class of technology that doesn’t create heat so much as move it around—and when they do so they only need to use a little energy to move a lot of heat.
Heat pumps can move heat from both inside to outside and outside to inside. Refrigerators are heat pumps that keep food cold by moving heat from inside the fridge to outside the fridge (cold is the absence of heat). Heat pump hot water systems are water heaters that collect 'free' heat from the ambient environment around your home and deposit it into your hot water tank for later use. 'Split system' RCACs (Reverse Cycle Air Conditioners) are heat pumps that can move heat in both directions, either cooling or warming your home as required. This technology is vastly more efficient than competing technologies, particularly non-electric technologies. In fact, RCACs are about 16 times more efficient at turning energy into heat than gas space heaters are, even before accounting for substantial losses in the gas supply chain.
Heat pumps can move heat from both inside to outside and outside to inside. Refrigerators are heat pumps that keep food cold by moving heat from inside the fridge to outside the fridge (cold is the absence of heat). Heat pump hot water systems are water heaters that collect 'free' heat from the ambient environment around your home and deposit it into your hot water tank for later use. 'Split system' RCACs (Reverse Cycle Air Conditioners) are heat pumps that can move heat in both directions, either cooling or warming your home as required. This technology is vastly more efficient than competing technologies, particularly non-electric technologies. In fact, RCACs are about 16 times more efficient at turning energy into heat than gas space heaters are, even before accounting for substantial losses in the gas supply chain.
The cost of switching to heat pump technology will depend on how your home or business is currently set up. In many cases it will cost nothing but in other cases there will be an upfront expense. It will cost nothing in the case that you already have an RCAC but are only using it in cooling mode and neglecting to use in heating mode—simply stop using other heaters and start using the RCAC in heating mode! In other cases, you may have to purchase a new appliance (and rip out an existing one). This can be expensive but will ultimately pay for itself over time because of lower operating costs. The same goes for EVs (Electric Vehicles), which are currently more expensive than alternatives yet are vastly more efficient at turning energy into motion and have much lower maintenance costs.
Typically the cheapest and fastest way to use energy more flexibly is to change your personal behaviours and program some appliances. If you're not at home to operate them yourself, most white goods (i.e. dishwashers, washing machines, and clothes dryers) have delay switches that allow you to run them while you're out of the home. As much as possible time these appliances to run around midday, because that’s when wind and solar generators run strong. In South Australia the electrical mix is an average ~85% renewable at 1pm, compared to a ~42% average at 7pm. The same goes for heating and cooling. Rather than running your heater overnight after you notice your home has become cold, take the initiative to program your RCAC to 'pre-heat' your home during the day so that it is still warm in the evening. Also, program your hot water system in the same way. There should be no need to replace entire appliances to make this happen. Worst comes to worst you can retrofit old appliances with inexpensive IoT (Internet of Things) devices that allow you to schedule them from your mobile phone. Retrofitting both your air conditioner and hot water system can cost as little as ~$250, including the cost of having an electrician wire one of the devices into your switchboard.
How do the principles relate to each other?
Helpfully, the principles reinforce each other: economy makes flexibility easier and flexibility can make efficiency more affordable. For example, airtight homes are more suited to pre-heating and cooling, which allows them to lower their operating costs by taking advantage of attractive time-of-use electrical pricing. In turn, those savings can be used to purchase more efficient appliances, which will make the home more economical yet again.
You should also keep in mind how the principles relate to each other at every new purchase.
Sometimes the principles will require you to reconsider. If you're considering rooftop solar panels to help electrify heating and cooling, first consider better home insulation. There's little point filling up a bucket with holes in it. Also, insulation may be more affordable and give you a better financial return.
Sometimes the principles will provide you with alternative solutions. If you cannot use an efficient RCAC or do not like the type of heat it produces, try an electric storage heater instead. Although they are less efficient they are also more flexible, as they can charge with energy during the daytime and release it as heat through the night (and they are still more efficient than wood and gas heaters).
Sometimes the principles will all apply at once. If you need personal transport, be economical and get only the smallest vehicle practical. If that must be a car, get the most efficient one possible—an EV if you can afford it. If you get an EV then be flexible and charge the battery on sunny days, ideally over the weekend when electricity demand is lowest and renewable generation may otherwise be curtailed.
What else is there to know?
Lots. But it's not hard to grasp. Watch this short talk for some more information to help you get started on your electrification journey.