Engineers often learn what they think they know is not what they need to know. In a similar scenario a particular supercomputer circa the 1980’s was cooled in a bath of liquid nitrogen.
When they put the prototype CPU in the liquid nitrogen it shorted in a microsecond as the whiskers came up. They learnt that what they had previously accepted as a polished surface was far from it in the new environment of liquid nitrogen.
I doubt that educational loop will ever be totally closed as technology goes from complexity to complexity.
A case study for you… we had a tiny 1.5kW system on our very large rental home in Sydney with significant shading throughout the winter, and we managed to save around $232 in one year on our electricity bill. The key was to use the ‘delayed start’ timer on the hot water loads on washing machine and dishwasher to run during solar-producing hours. The other key was to switch to a flat rate tariff (one call to the energy retailer), which made a difference. With two adults working out of the home and two children, we were definitely using most of our electricity during peak periods, so paying a lower flat rate was well worth it for us.
We were on a 24c/kWh usage tariff, and a 13c/kWh solar feed-in tariff. We produced 1.2MWh of solar over the course of a year and consumed 4.2MWh over the same period (not at the same time during the day of course!). Here are our production, consumption and our savings for one year (21st July 2018 - 20th July 2019):
These figures don’t include the additional daily supply charge of around 90c per day and it’s worth noting that we had gas hot water, so our overall electricity usage is lower than a 4-person family with electric hot water.
The savings we had in one year wouldn’t pay off a new system quickly, but if it was our house and we had put the solar on ourselves, we would have been conscious of the huge gum tree at the front of the property creating shading nearly all winter when choosing the position and sizing of the system (and likely choosing to use micro-inverters so we could get per-panel solar production when there was shading). And I imagine that the owners took advantage of the high solar feed-in tariff when they put the solar on 9 years ago and paid it off fairly quickly. So we’ll take the free solar energy - thanks very much!
Hi Steph, I don’t know where you are located, but the winter “expected” output seems remarkably high for Southern Australia, and summer a bit on the low side. For July production to be as good as February is unusual, even Townsville in Qld would get 30% more in summer than winter.
Many people would be very happy if their winter production was only 15-20% less than summer… but maybe you are located near Cairns
For Sydney, in a year a typical north facing 1.5kW system according to the CEC would be expected to produce approx 365x5.85kWh. Or 2.14MWh.
Note: Total annual Solar irradiance varies +/-10% or more. Some years are sunnier and others less than the guide. A system may appear to perform better or worse as a consequence of this variation.
Your observed 1.2MWh is certainly much less. As well as winter shading, the age of the system may also be a factor in the reduced performance. You did not mention the roof panel orientation was a factor. The total production for each of the summer months Nov - Feb seems low compared to a newer system which would deliver closer to 250kWh per month in summer and 100kWh per month in Winter. Perhaps Sydney had an exceptional wet and overcast summer for 4 months?
P.S. noted your charts run on a financial year.
I have a 3kW nominal system in Brisbane only 8 months old. It is averaging more than 13kWh per day, slightly better than the CEC guide. It has been dry though. The total bill is in credit, although a large portion of the feedin credits go to offset the fixed daily connection and metering charges.
