This was our second power bill and it covered the period from 21/03/2023 – 19/06/2023. The bill was $181.50. The net cost of grid power (after FIT credit applied) was $115.44 and the connection charge was $66.07.
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 673.01kWh of electricity from the grid. The solar monitoring app (the basic one that came with the solar package) shows that we used 1011.95kWh of solar power over the same period. This gives a figure for the total power used in the house over the 91 days of 1684.96kWh, or average daily consumption of 18.5kWh.
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 $473.85. Rooftop solar has saved me $339.80 this quarter.
By comparison to our summer bill, we have used slightly less grid power (673.01kWh versus 703.64kWh) and less total power (1684.95kWh versus 2028.71kWh). The RCAC wasn’t required to maintain a comfortable temperature in the house. We generated enough heat with a combination of the thermal mass in the ground-floor slab, the oven for evening meal preparation and the intermittent use of 2 heated towel rails.
Not surprisingly, there was a noticeable reduction in power generated by the roof-top solar system. This was not unexpected. Our flat roof slopes at 5° the SW and I made a decision not to put the PV panels on stands to raise them towards the north for aesthetic reasons. We exported 624kWh, compared to 1785kWh over the period of the summer bill.
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 0.37kWh from the grid and 7.1kWh from the roof for electric hot water.
Quarterly Electricity Consumption and Charges
21 Mar. 2023 - 19 Jun. 2023 | Period Total (91 Days) | Daily Avg. |
Grid Electricity Consumption | 673.01kWh | 7.39kWh |
Roof-top Solar Consumption | 1011.95kWh | 11.12kWh |
Total Power Consumption | 1684.96kWh | 18.5kWh |
Roof-top Solar Export | 624kWh | 6.8kWh |
Value of Grid Electricity | $162.89 | $1.79 |
Value of Exported Electricity | $47.45 | $0.52 |
Net Electricity Charge | $115.14 | $1.26 |
Network Connection Charge | $66.07 | $0.72 |
Bill Total | $181.50 | $1.99 |
Bill Total (non rooftop solar case) | $473.85 | $5.20 |