Got Solar? Use Water as a Battery!

Recently Australia reached a milestone of 3-million ‘small-scale’ solar systems installed on homes & businesses. That’s more than 1 in 4 houses!

Unfortunately, for many WA households, a large portion of their solar power is exported to the grid for a measly 2.75cents/kWh feed-in tariff, only to later repurchase it from the grid in the evening for 29.3 cents/kWh. What a gyp!

 Not surprisingly, many solar system owners are wondering how they can avoid this…

 Shifting electricity usage into the daytime is one strategy we recommend. For example, running the pool pump, clothes washing machine and dishwasher during the day instead of night. But even then, many families still have high night-time electricity usage.

 Another solution gaining popularity are Home Energy Storage Batteries. At Positive Energy Solutions we find that 1 in 5 of our customers are now purchasing a Battery with their new Solar Panel System. Our most popular options being:

 For some customers though, battery prices don’t quite fit the budget. There is, however, a much more affordable way to store some of that excess solar energy…

A major energy cost for most families (often around 20%) is for heating water using a Gas or Electric Resistive hot water system. But a smarter, more efficient solution gaining favour is the iStore Hot Water Heat Pump AKA “Thermal Battery

An iStore Heat Pump will use your excess solar power to heat water and store it in a tank for later use, not unlike how excess solar power can be stored in a battery.

 Hot Water Heat Pumps are a similar technology to fridges and air-conditioners which use a refrigeration cycle to transfer heat. However, rather than using the cooling effect, a Hot Water Heat Pump works in reverse (just like a reverse-cycle air-conditioner does when on heating mode)

1. A fan draws in air, containing ambient heat energy, which blows across the evaporator.

2. The evaporator turns the liquid refrigerant into a gas (CFC Free R134a)

3. The compressor pressurizes the gas making it very hot.

4. The hot gas inside the condenser coil (wrapped around the tank) heats the water inside

5. After transferring the heat to the water tank, the refrigerant gas turns back into a liquid, returning to the evaporator for the process to start again.

6. The cycle continues until the set water temperature is reached.

7. As hot water is used in the home, the cycle will restart if the water temperature inside the tank drops below 45°C

The Economics

If you currently have a Gas hot water system, an iStore Heat Pump is a very sensible investment. Especially if your current hot water system has a low star rating or is due for replacement anyway.

Just like grid electricity, gas prices are also increasing. Currently, the price of gas in WA is equivalent to 15.35 cents/kWh. So, rather than selling your excess solar power to the grid for only 2.75 cents/kWh, you can use that power to heat water more cheaply than by using gas. This change boosts the value of your excess solar power by at least 5 times.


270L iStore Running Cost Per Year*

* Savings are based on a family of 4 consuming 200 litres per day for one year. Tariffs based on $0.25 per kWh for electricity, Natural Gas price of $0.0351 c/MJ & LPG price of 1.25 $/L. Actual savings may vary on household usage, solar power system and climate conditions.
How much excess solar power do you need?

One common question we get asked is how much excess solar power is required to run a Hot Water Heat Pump?

The 270L iStore Heat Pump draws 1000W of power and usually runs about 4 hours per day. Or the smaller 180L iStore draws only 500W of power.

 So, for most typical size homes, the answer is about 2 – 4 kWh per day.

 Considering the average solar system size these days is around 6.5kW which generates approximately 28kWh per day on average, rest assured there is usually plenty of excess solar power available for powering the iStore Heat Pump.

 Our Advice: Instead of paying around $500 per year for gas to heat water, use your excess solar power instead which Synergy values at only $30 per year.

 Interested in the iStore Heat Pump? Request a Quote today and receive up to $1,000 STC Discount


Give us a call today and one of our friendly and super knowledgeable energy consultants will be able to assist you with your enquiry.

1300 180 999 

[email protected]

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