Assumptions are all very well, but real data takes out solar guesswork

MyEnergy app screen shot extract


When school teacher Kristian Jackson wanted to invest in rooftop solar, he found his Wattwatchers device and MyEnergy app invaluable for sizing the right system.

Living in the foothills of the notoriously chilly-in-winter Blue Mountains, west of Sydney, Kristian and wife Natalie have been relying on running their ducted air-conditioning in heating mode to warm their family’s all-electric home in the colder months of the year.

To say it’s an energy-guzzler is an understatement, because the data shows on some days their daily household consumption has been soaring above 100kWh a day, adding $25 or more a day to their pre-solar monthly power bills.

MyEnergy app screen shots from Blue Mountains home
On a July winter’s day the Jackson’s electricity usage soared as they tried to keep warm, but by November they were using less than a fifth of the electricity on a late spring day.

When the Jacksons started talking with solar installers to get quotes for a rooftop system, they found the focus quickly shifted to the common assumption in Australia: namely that maximum consumption is driven by air-conditioning in summer, and also pool pumps if the house has one.

Thanks to the MyEnergy app, Kristian knew this was way off the mark for their home, and he had the hard-data evidence to back it up.

‘Our place is easy to cool in summer, and we can run the air conditioning at 26/27 degrees C no problem, which is great during the hotter months,’ says Kristian, ‘but that means it’s freezing in winter!’

Kristian recalls feeling empowered because he knew more than the would-be installers, and the data helped them to arrive at a 12kW system (premium LG panels and twin SolarEdge inverters) costing around $15,000.

To get an idea of the huge variability in electricity consumption that the Jacksons have been experiencing, consider these monthly breakdowns – all from before their solar system was installed and went live in November 2021:

  • January 2021 – total 1297kWh usage and daily average of 41.84kWh
  • April 2021 – total 1160kWh and daily average of 38.67kWh
  • July 2021 – total 2499kWh and daily average of 80.61kWh
  • October 2021 – total 914kWh and daily average of 29.48kWh
MyEnergy app grid history screen shots from Blue Mountains home
What a difference a few months can make! With solar now added (right), the Jacksons are hoping that their high consumption from the grid on a winter’s day in July 2021 won’t be repeated in the 2022 winter.

The big challenge in the data, and the reality for the Jacksons, is that winter will simultaneously be their worst season for solar generation and their biggest season for total consumption.

With a view to ensuring their new solar does help to get their winter power bills down, Kristian agrees they have deliberately oversized their system. This means they’ll be a small local power station, with 40KWh+ solar generation on sunny spring-summer days, pumping out clean energy from the sun to their neighbours.

But he’s happy with a projected payback period on their solar investment of 3.5 years. And the Jacksons are expecting winter heating costs to come down significantly next winter because as well as installing solar, they’ve replaced a heat-leaking old non-insulated tile roof with Colorbond, complete with new insulation.

Kristian confesses to being a ‘bit of a data nerd’, and has the full suite of common motivators for investing in solar: financial, environmental, with a dash of independence and self-sufficiency too. ‘At first the app was a nice-to-have,’ he recalls, ‘but it became indispensable and I felt so empowered when talking with solar installers.’

Over the year ahead, now their solar is up and running, the MyEnergy app will be helping them to optimise self-consumption of their solar to maximise reductions in their power bills. It also can help them to find the best electricity tariff deal for their scenario, and it will verify how their big investment in solar and a new roof is tracking year round.

One clear opportunity from the data is to reset their electric hot water system, currently an ‘uncontrolled load’ which reheats whenever hot water is used (often at night), so that it powers up in the middle of the day when solar is likely to be available.

Kristian says he’s feeling even more empowered by the MyEnergy app, now that it’s helped him to pinpoint the opportunity to bring hot water heating under his solar curve – and he’s already been in touch with his energy retailer to make this happen. The image below shows how December 2, 2021, was a big solar generation day for the Jacksons – but most of the hot water heating load missed the free electricity from the sun.

FOOTNOTE: The Jacksons were installed with a government-subsidised Wattwatchers device for their home in December 2020, under the My Energy Marketplace (MEM) project led by Wattwatchers with grant funding support from the Australian Renewable Energy Agency (ARENA)*.


The My Energy Marketplace project is receiving funding from ARENA as part of ARENA’s Advancing Renewables Program. The views expressed herein are not necessarily the views of the Australian Government, and the Australian Government does not accept responsibility for any information or advice contained herein.