OneTaskBy Tim King · Updated
Solar Installation Cost Calculator
Price per Watt Quote, Battery Cost, Rebates and Panel Count
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How the Solar Installation Cost Calculator works
This solar installation cost calculator estimates what a home solar panel system costs. Enter the system size in kW and the installed price per watt from your quotes, the panel rating, an optional battery at your price per kWh, extras and any rebate or grant you qualify for. It returns how many panels, the gross and net cost and the net cost per watt. It has no built-in prices or incentives; get local quotes.
Installers quote a whole-system price, and dividing it by the system's watts gives a price per watt that lets you compare quotes of different sizes fairly. Larger systems usually cost less per watt, because scaffolding, the inverter, design and paperwork are spread over more panels.
How the solar installation cost calculator works
The formula is panels cost = kW × 1,000 × price per watt; battery = kWh × price per kWh; gross = panels + battery + extras; net = gross − rebates; panels = kW × 1,000 ÷ panel watts, rounded up. For example, a 6 kW system at 1.50 a watt is 9,000; a 10 kWh battery at 600 a kWh adds 6,000 and extras 500, a gross cost of 15,500, or 13,500 after a 2,000 rebate, which is 2.25 a watt net, using 14 panels of 430 W. A second example: without the battery the net cost is 7,500, or 1.25 a watt.
To size the system, use the solar sizing calculator, and to see how many years it takes to pay back, the solar payback calculator. Rebates, grants and tax credits change often and depend on where you live, so enter only what your installer or government site confirms.
System cost by size and installed price per watt, before battery and rebates
| System size | 430 W panels | At 1.00 a watt | At 1.50 a watt | At 2.00 a watt | At 2.50 a watt |
|---|---|---|---|---|---|
| 2 kW | 5 | 2,000 | 3,000 | 4,000 | 5,000 |
| 2.5 kW | 6 | 2,500 | 3,750 | 5,000 | 6,250 |
| 3 kW | 7 | 3,000 | 4,500 | 6,000 | 7,500 |
| 3.5 kW | 9 | 3,500 | 5,250 | 7,000 | 8,750 |
| 4 kW | 10 | 4,000 | 6,000 | 8,000 | 10,000 |
| 4.5 kW | 11 | 4,500 | 6,750 | 9,000 | 11,250 |
| 5 kW | 12 | 5,000 | 7,500 | 10,000 | 12,500 |
| 5.5 kW | 13 | 5,500 | 8,250 | 11,000 | 13,750 |
| 6 kW | 14 | 6,000 | 9,000 | 12,000 | 15,000 |
| 6.5 kW | 16 | 6,500 | 9,750 | 13,000 | 16,250 |
| 7 kW | 17 | 7,000 | 10,500 | 14,000 | 17,500 |
| 7.5 kW | 18 | 7,500 | 11,250 | 15,000 | 18,750 |
| 8 kW | 19 | 8,000 | 12,000 | 16,000 | 20,000 |
| 8.5 kW | 20 | 8,500 | 12,750 | 17,000 | 21,250 |
| 9 kW | 21 | 9,000 | 13,500 | 18,000 | 22,500 |
| 9.5 kW | 23 | 9,500 | 14,250 | 19,000 | 23,750 |
| 10 kW | 24 | 10,000 | 15,000 | 20,000 | 25,000 |
| 10.5 kW | 25 | 10,500 | 15,750 | 21,000 | 26,250 |
| 11 kW | 26 | 11,000 | 16,500 | 22,000 | 27,500 |
| 11.5 kW | 27 | 11,500 | 17,250 | 23,000 | 28,750 |
| 12 kW | 28 | 12,000 | 18,000 | 24,000 | 30,000 |
FAQ
How much does a solar panel system cost?
Multiply the system size in watts by the installed price per watt you are quoted. A 6 kW system at 1.50 a watt is 9,000 before any battery, extras or rebates. Prices vary by country, roof and installer, so get at least three quotes and compare their price per watt.
How many solar panels do I need for a 6 kW system?
Divide 6,000 watts by the panel rating. With 430 W panels that is 13.95, so 14 panels; with 400 W panels it is 15. Each panel is about 1.7 by 1.1 m, so check how many fit on your roof before choosing the size.
Is a solar battery worth it?
A battery stores daytime solar for the evening, so it pays off when the gap between what you pay for grid electricity and what you are paid for export is large. Compare its cost with the extra savings per year; batteries often take longer to pay back than the panels.
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