Our first quarterly power bill was $99.95 (inc.GST). It was for the period from 21 December 2022 to 20 March 2023. The net cost of grid power (after FIT credit applied) was $34.61 and the connection charge was $65.34.
The house is completely electric, with a 7kw solar PV system on the roof. The inverter is 6.6kw and we have opted against a home battery. We are a household of 3 people. At present, we pay a flat rate of 24.2c per kWh of electricity and get a feed-in tariff of 7.6c. Our charge for being connected to the electricity network is 72.6c/day.
The bill shows that we used a total of 703.64kWh of electricity from the grid. The solar monitoring app (the basic one that came with the solar package) shows that we used 1325.07kWh of solar power over the same period. I cannot asses the accuracy of these app figures. There was a discrepancy of 87 kWh when I compared the figures provided by both for solar buy back, or feed in, whichever terms you prefer.
Nevertheless, if I use the grid power figure provided on the bill and the solar self-consumption figure provided by the app, I get a figure for the total power used in the house over the 90 days of 2028.71kWh, or average daily consumption of 22.5kWh. I thought it would be an interesting exercise to calculate the cost of power if we didn't have rooftop solar. The bill would have been a total of $556.28. Rooftop solar has saved me $456.33 this quarter.
Our air-conditioning system is a ducted 7kw system. There were 10 days in March 2023 where the temperature rose over 29°c and 4 of those were above 35°c. I recall running the a/c for 24 hours around these very hot days and about 6 hours on the others. Our hot water heater is a 315L Solahart Powerstore. We are a small family but I have been impressed with how little grid power it has used. Per the app data, we used a daily average of 0.13kWh from the grid and 5.8kWh from the roof for electric hot water.
Quarterly Electricity Consumption and Charges
21 Dec. 2022 - 20 Mar. 2023 | Period Total (90 Days) | Daily Avg. |
Grid Electricity Consumption | 703.64kWh | 7.8kWh |
Roof-top Solar Consumption | 1325.07kWh | 14.7kWh |
Total Power Consumption | 2028.71kWh | 22.5kWh |
Roof-top Solar Export | 1785kWh | 19.8kWh |
Value of Grid Electricity | $170.28 | $1.89 |
Value of Exported Electricity | $135.67 | $1.51 |
Net Electricity Charge | $34.61 | $0.38 |
Network Connection Charge | $65.34 | $0.72 |
Bill Total | $99.95 | $1.11 |
Bill Total (non rooftop solar case) | $556.28 | $6.18 |