Solar soak

Are you getting the best value from your solar PV system? Despite what most people think, it’s not in everyone’s best interests to export as much solar power as they can back to the electricity grid. Using more of your solar energy at home is becoming more important as the value of exporting electricity declines from year to year.

Who should be exporting back to the grid?

If you're on the 44c Solar Bonus Scheme feed-in tariff, you'll most likely benefit financially by exporting solar power back to the electricity grid. However, at certain times solar exports are not needed by the electricity grid and can cause problems in the system.

However, for everyone else, using as much solar power as they can in their own home and only exporting what they can’t use, gives the best value from their system. This is because the cost of electricity from your rooftop solar system is much less than the amount you pay to buy electricity from the grid through your retailer.

The following information about maximising solar soaking is directed to customers who are NOT on the 44c Solar Bonus Scheme feed-in tariff.

We outline a range of tips below to explain how the get the best out of your solar system by "solar soaking".

Solar soaking

Using your own solar power is called ‘solar soaking’. It’s when you use more solar power in your home than you export to the grid. It’s how you get the best value from your system and maximise the use of renewable energy.

Your power bill shows how much solar power you export to the grid. If you're exporting more than around 8kWh/day or 700kWh over a quarterly billing period, and you are NOT on the 44c Solar Bonus Scheme feed-in tariff, you'll most likely benefit by using more solar power at home and reduce your bill.

Using appliances when your solar PV system is generating the most electricity (usually from 8am to 4pm in summer or 9am to 3pm in winter), it's possible to save hundreds of dollars on your power bill each year.

We've complied this Solar Soak Factsheet (PDF 2.4 mb) that solar PV systems owners can download, and solar installers can also use and provide to their customers.

Solar soak calculator

How much might you save by using more of your electrical appliances between 10am - 2pm so that they use electricity generated by your rooftop solar? We've put together this very simple calculator. It gives a general idea of the savings you might find from using different appliances. As all individual circumstances are different and the input power (ie amount of electricity used) by an appliance may vary, this calculator can only be considered as an indicative guide of possible savings you could make.

IMPORTANT: This calculator is not suitable for customers with export limits on their solar system.
About your rooftop solar
What is the normal cost of electricity (c/kWh) you are charged between 10am - 2pm on a weekday?
c/kWh (inc GST)
What are you paid (c/kWh) by your Retailer for sending electricity (exporting) back to the network?
c/kWh (inc GST)
What is the size of your solar panel array on your roof (kW)?
Estimated average daily export from your sized solar system (if not export limited)~.
Appliances you could change to run between 10am to 2pm
Tick the boxes that apply to you.
Pool pump (Energy efficient)
Pool Pump (fixed speed)
Hot water (element)
Hot water (Heat pump)
Clothes Dryer (element)
Washing Machine
Air conditioner
* To minimise any use of network supplied electricity and possibly increase your savings, make sure that
(i) the kWh don't exceed what you would export daily, and
(ii) the total of the loads (calculated by adding up the input power of each appliance) does not exceed your solar inverter's capacity,
or your savings may be less.
~ A solar PV system produces about 4 times the electricity (kWH) of its size (kW). Average daily export is based on customers exporting approximately 55% of their daily generation (if not export limited).
  • Pool pump: Energy efficient pool pump uses 400W, a fixed speed uses 1kW for the full four hours
  • Hot water: Element is 1.8kW running for 2 hours, Heat pump is 1kW for 3 hours
  • Clothes Dryer: Single, 1 hour dry daily, 2.4kW rated load
  • Dishwasher: 2 hours daily, 2.4kW rated load
  • Washing Machine: 1 hour, 5 times a week, 500W, warm wash cycle with hot water from tap.
  • Air conditioner: 6kW cooling capacity reverse cycle single-split system, 1 hour during summer weekdays, at full capacity. 1.5kW load
  • Oven: 1 hour, 5 times a week. 3.6kW load
The above calculator is provided as an indicative guide of possible savings that a typical customer with rooftop solar might be able to achieve by using more electrical appliances between 10am – 2pm. The calculator uses various assumptions of input power used by electrical appliances and is not tailored to your household situation and the actual input power of the electrical appliances that you own. [Energex/Ergon Energy] does not guarantee that you will necessarily achieve the level of savings that the calculator shows may be possible and accepts no liability to you in respect of the use you make of the calculator and any subsequent decision you may make to change your electricity usage habits.

Free things you can do to save now

Here’s some no-cost options that you can do right now:

  • Sun's out? Turn it on! If you're home during the day, simply use appliances like dishwashers, washing machines, clothes dryers, irons, vacuums, stove-tops and ovens when your solar is generating. For high energy consuming appliances like corded vacuums, irons, stove-tops and ovens, stagger their use during the day to make the most of the solar power that's generated. Where practical, charge laptops, iPads, power tools and other items during the day.

Tech Tip – to really save, it’s good to understand how much power your solar PV system is generating. Most inverters have a display that shows you this information, and many models also have an app to display this information on your phone. If your inverter doesn't have this capability, you can install a basic Home Energy Management System (HEMS) - cost around $200 plus installation - that will display how much power your solar PV system is generating and how much you're using on an app. A more advanced HEMS can also control some appliances for you, making things even simpler.

  • Not at home? Use appliance timers. Many appliances like dishwashers, washing machines and clothes dryers have built in timers that let you control when they come on – you can use these functions to stagger when these appliances operate during the day. For example, you might program your dishwasher to come on at 9am, and your washing machine at 11am.

Tech Tip – if your current appliances don’t have timers, and you’re not usually home during the day, you can switch these appliances on as you leave home in the morning to utilise the morning solar power generation. If your current appliances don’t have timers, be sure to look out for this function next time you buy.

  • Got a pool? If you have a pool or spa filter on the same tariff as your solar PV system, ensure it's set to run during the day when your solar PV system is generating power.

Tech Tip - if your pool or other appliances are connected to an economy tariff (like tariff 33 or tariff 31), your solar PV system does NOT power these, so you will not directly benefit from changing the time when these appliances run, however you will be helping relieve the energy network from too much exported solar generation.

  • Get home after 5pm? If you arrive home after 5pm on hot summer days and your air conditioner has a timer or can be turned on remotely (i.e. through Wifi / or an app), consider switching it on an hour or two earlier so your solar power can run your air conditioner and pre-cool your home for your return.
  • Love a good curry or stew? Preparing your evening meal in a slow cooker turned on in the morning not only means your meal is ‘solar powered’, you get the benefit of having your dinner ready to eat when you get home!

Low cost things you can do to save

  • Appliances with timers - When buying new appliances like dishwashers, washing machines and clothes dryers, look for models that have built-in timers, or even better, can connect to the internet to allow you to schedule when they run.
  • Electric hot water - Do you have an electric hot water system? If you have a large amount of solar power generation that's being exported during the day, an electric hot water system can be utilised to soak up that electricity in your home, if your hot water system is connected to the same tariff (ie tariff 11). A simple way to do this is to install a timer so that your electric hot water system operates when your solar is generating.
  • Install a Home Energy Management System (HEMS) - this allows you the best control of your appliances and setting them to run during the day when your solar PV system is generating and gives you the ability to boost your electric hot water system on days when your hot water demand is highest.

Higher cost, higher savings things you can do to save

  • Do you have gas hot water? When your current system needs replacing, a good option is to switch to an electric hot water system on a timer to heat up during the day. With your new hot water system not on an economy or night rate tariff, you effectively have a solar powered hot water system. Plan ahead so that you are ready when the time comes to make the switch.
  • Store your own solar power - If you're exporting a lot of your solar power to the grid, consider purchasing a battery energy storage system (BESS) to store that energy. Then you can use your free solar power later at peak times to reduce what you buy from the electricity grid at full price. A BESS can also be configured to provide you with electricity on essential circuits during power outages, especially after storms or other natural disasters. You can find more information as to whether a BESS is right for you.
  • In the market for a new car? You may consider an electric vehicle that you could charge during the day with your excess solar generation.