For potential owners of solar panels, Sunshine Coast residents can always rely on home and energy to provide real calculations – to show why solar power is such a good investment.
This case study investigates the advantages of both a 3kW and a 5kW solar system for a household.
On this house, the solar panels would be mounted in an East/West orientation.
The average daily electricity usage is around 25kWh per day. Of this 8kWh is the hot water. As this is on the off peak it is costing around $147.50 per quarter.
From investigation, I have calculated the daytime consumption for the appliances that run every day, or almost every day.
Appliance daytime consumption:
Fridge – 1.5kWh/day
Washing machine – 2kWh/day
Swimming pool pump – 3kWh-4kWh/day
Lighting – 0.5kWh/day
TV, radio, computers, phone, ceiling fans – around 1.5kWh/day
Toaster, kettle – breakfast/lunch cooking – 0.5kWh/day
Estimated total daytime consumption – 17.5kKh
The assumed self-consumption for the 3kW system is 80% consumed and 20% sent back to the grid. For the 5kW system, 70% has been consumed and 30% fed back to the grid.
- A 3.12kw system, 12 panels- will generate 12.5kWh/day on average.
- This system would replace almost all the daytime consumption if the hot water stayed on the off peak.
- Using solar system of 3kW inverter at a cost of $3,600 – fully installed – the savings would be:
- Quarterly – $248.37;
- Annual – $985.37
- After 5 years @ 3% increase in electricity prices – $5,047.30
- ROI – 26.58%
- The solar rebate for a 3kW system is around $2,390, which is the minimum value it would add to the home.
- A 5.2kw system, 20 panels- will generate 20.8kWh/day on average.
- This system would replace almost all the daytime consumption including the hot water;
- Using Solar system inverter at a cost of $5,700 – fully installed, including a replaced hot water element and timer switch – the savings would be:
- Quarterly – $386.16;
- Annual – $1,532.04
- After 5 years @ 3% increase in electricity prices – $7,907.64
- ROI – 26.38%
- The solar rebate for a 5kW system is around $3,990 which is the minimum value it would add to the home.
The ROI is similar for both systems. The 5kW is a larger investment, however, over the 5 years the household is $2,200 ahead and the system has been paid off.
With the 3kW they are $1,440 ahead and the system is paid off.
Looking at the figures, the 5kW system is a better investment; however, the capital costs are higher.
With the 5kW system, the annual savings over 15 years would be – $26,410.14.
The 3kW system 15-year savings would be – $17,140.74