A customer Rob, came into our main street office last week. We had previously helped to install solar on his elderly parent's home in July last year.
You know we love our data here at Geni.Energy and we love to base decisions on fact, so here is a deep dive that might help you too!
He had just received her quarterly bill and it was higher than he had expected, having installed a 6.6kW solar system in July 2023. As they had never installed the app that comes with the solar inverter, they could not tell what was happening with their solar and were suspicious that the solar system was not working properly.
Rob's mother's quarterly bill this time was $890 (for January to April) and it said that there was average general consumption of 18kWh/day and controlled load consumption of 6kWh/day for the electric hot water system, along with 18kWh/day of export of excess solar.
Although at a quick glance it was hard to tell, after our deep dive we realised Rob's parents would have paid off their solar system in bill savings in just three years. So read on to find out how.
Because Rob had used Geni.Energy for the solar installation and we are locally based, our technical officer Geoff, ducked around to Rob's mother's house to step him through how he can read and understand the read-out screen on the front of his solar inverter.
The screen was able to tell him exactly how much electricity was being generated at that moment.
The 6.6kW system on the roof has a 5kW inverter which means that the maximum electricity that could be generated at any one moment in time is 5kWhs (kilowatt hours) and if it generated that for one hour he would have 5kWh of electricity to use in the house, with the extra going to the grid at any one moment in time.
On a bright sunny day Rob could expect around 6 hours of sun, giving him a maximum of (6 hours times 5kw) 30kWh of generation and on a winters day he might get 3 hours of full sun making (3 hours times 5kw) 15kWh of electricity per day.
So his read out panel showed 5kWh of generation in the middle of the day so straight away he knew that his solar panels were producing properly.
The next step was to work out what was happening with his generation and consumption during different times of the day. To do this we applied to our network provider, Essential Energy, to access his data in half an hour increments.
On receiving Rob's data back we were able to make some accurate assumptions about what was happening and why his mother's bill was what it was.
When we looked at a day last week we found that the house created an excess of 18kWh of electricity that it sent to the grid, after it offset basically all of the house consumption from 8am to 3.30pm. What we cannot tell from the data is how much consumption was happening in the house that was immediately met by the solar just doing its job. This data is at the meter, when the house meets up with the grid (and Essential Energy's network).
We also found that the hot water used about 10kWh which all came from the grid and about 13kWh was imported from the grid from around 4pm through to around 8am the next morning.
When customers are willing to change their habits of electricity use, even greater savings can be made, but in Rob's parents' case, they are elderly and didn't want to bother with all that and wanted to enjoy their sunset years in comfort.
So at 43c/kWh it cost Rob's mum $5.60 for the general overnight consumption and at 24c/kWh it cost her $2.40 for the hot water electricity. Meanwhile her excess solar, at 7c/kWh created a $1.30 credit for the day, totalling $6.70 for the day.
We all know electricity prices have been going up, but some don't realise this includes the daily charge that we see on our bills as well. In Rob's case it is $1.90 per day supply charge, so straight up his quarterly bill starts with $170 fee.
Some simple change of habits, moving some consumption to solar times can create more savings. We encourage you not to "set and forget" but to actively keep an eye on your generation and consumption and make changes that improve your savings.
When we make a direct comparison with the same day last year for Rob, prior to the solar being installed we find some interesting things.
Firstly, last year for this one day the home consumed around 7kWh for hot water and around 30kWh for the rest of the electricity. At today's prices, the cost of just the electricity for this one day would have been $14.60, a 65% savings! The quarterly bill at today's prices would likely to have been around $1,500.
Electricity consumption happens in every split second and this is all added up to make a quarterly bill, however its the thousands of little decisions you make each day that accumulate to have a big impact on your bill. Even the seasonal variations can have overall a large impact.
There are some days where 2kWh were being used each hour from 5am through to 8am. Even through the middle of the night there is still 0.5kWh being used each half an hour, adding up over the whole night. These are the things that solar cannot help with, only batteries (storing excess solar from the day) can offset that usage.
We logged into the app for Rob to find out what the gross generation on the system is as a cross check for the bill and the data. On these autumn days at the moment the system is producing about 23kWh each day.
The interesting thing about this data is that it is "in-front" of the meter, so it is the gross generation that the solar system makes in the day. You can see there are moments when a cloud reduces the generation for a few minutes etc, showing how incremental the solar generation is.
Over the last few months, you can see that the summer months can produce 1,200kWh (an average of 38kWh per day), where as April produced 700kWh (or an average of 23 kWh per day).
Overall, I would say this solar system is working really well!
A summer's day last year Rob's mother's system had a net consumption of 29kWh plus 6kWh for hot water and exported 29kWh. Most of the extra consumption was the evenings,
A winter's day after the solar was installed saw hot water consume 11kWh, general consumption from the grid at 32kWh and export to the grid at 14kWh. This shows more usage overnight, assuming heaters are running and less solar generation due to shorter days.
When looking through the data, showing the behind-the-meter consumption and generation for each and every half an hour for the last year we see a few things:
The solar hours' consumption are fully offset by the solar generation - this means the solar system is well sized for the home's consumption levels
There is excess solar generation during the day so the electric hot water could have a timer installed so that it draws electricity to heat the water only during solar hours, but this only costs 24c/kWh, sacrificing the 7c/kWh credit for the excess solar that is exported to the grid
There is night time usage occurring, some of which might be able to be shifted to the day time to utilise the excess solar
There are savings being made from having solar, but these are currently blurred by electricity retailers raising their prices for both electricity and daily fees, whilst reducing the feed-in-tariff for excess solar
A $590 quarterly savings off the electricity bill ($1, 484 - $890) is a $2,360 savings per year. At our current system price, the savings over a three year period would have paid for the system. The solar panels have a 25 year warranty and the inverter has a 10 year warranty so at a bare minimum, that gives Rob's mother over $17,000 worth of savings over the lifespan of the inverter, or 7 years of free solar power!
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