Case Study - customer saves $650pa in water heating costs

This great case study from solar installer Roofjuice shows the power of Solar Analytics' solar monitoring to save hundreds of dollars for their customer:

This week we witnessed an example of the incredible power - and value - of installing smarter solar instead of dumb solar.

Quite simply, our smarter solar systems provide valuable information that allows users to understand their energy consumption, maximise self consumption by controlling loads and generate more energy in difficult sites.

Our customer has a pretty typical home, equipped with all the mod cons – dishwasher, ducted AC, pool and electric hot water. Their energy consumption is fairly significant at around 30-40kWh per day. We recently fitted out their home with a 5kW East/West oriented solar system equipped with Solar Analytics monitoring and a SunMate solar diverter.

We visited the site as part of our scheduled internal audit program and to check on the results, and along with the homeowners, were blown away with what we were seeing.

Firstly, using a mobile phone we were able to log in and watch exactly what was being generated and used in real time. This allowed us to confirm that we had matched the system size to the consumption really nicely and that everything was working as expected. While we were showing the customer this we suddenly noticed a spike in the load and discovered that Nan had put the kettle on and was toasting crumpets in the granny flat – a great real world example of how energy was being consumed.

Secondly, this property also has a solar diverter installed which is designed to dump excess solar energy into the hot water tank instead of exporting it into the grid.

We watched with great delight - as the solar generation increased, so too did the diversion. Some of the occupants had left for the day so as the load decreased, the excess increased and more and more was diverted.

But here’s the outstanding proof of concept.

Using Solar Analytics monitoring, we could see that before the diverter was commissioned, the hot water system was triggered for off peak at midnight and ran for around three and half hours, using around 14kWh of energy. Read more about how to reduce your hot water bill.

With the solar diverter installed we could see that the excess energy in the morning was being diverted to the hot water tank throughout the morning and by midday, had throttled back – the water was hot. Throughout the afternoon, it throttled on and off at a lower level, keeping the water warm. Then at midnight as planned, the off peak was triggered as usual. However, because the water was already hot from the solar it ran for around 15 minutes. Although it will vary throughout the year, in rough terms this equates to a saving of more than 5000kWh p.a. or $650 p.a. in water heating costs.

Solar Analytics solar and energy monitoring graph

But we aren't done yet!

We can now see there is still some excess energy being exported in the afternoon (after the water is heated), and we can measure exactly how much there is because we are monitoring it in 5 second increments.

So now, we are building a picture of what to do with that excess. There is the option of batteries of course, which we can perfectly match – and even simpler, a second load diversion to their pool pump and filter.  We can monitor the demand of the pool pump (currently running on a standard timer) and confirm how much energy it needs, then reprogram the diverter when we are ready. Even better, we can predict that as summer approaches the excess solar will increase and, the water heater won't need so much energy because average ambient temperatures will have increased too, and pool filtration needs will also increase.

Our clever little system will then automatically start diverting more to the pool pump and less to the hot water.

If that isn’t smart, I don’t know what is.

Outcomes and lessons

We learned several things form this site.

Firstly, it's the power of great monitoring in education and changing behaviour. They had no visibility of how, when or why energy was used previously – just a big bill.

Secondly, that by taking small steps – measure, analyse, change then repeat - we can minimise impacts and maximise performance, even as demands and seasons change.

In this case a cheap, unmonitored dumb solar system would have simply been dumping loads of excess energy into the grid.

Check out more case studies to learn more about how Solar Analytics monitoring to help you get more value from your solar power system.

Solar Analytics
We are Australian Photovoltaic Engineers, Software Developers, Scientists, Solar Technicians and Designers, all passionate about sustainable energy and the power of solar.
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