Solar & battery
Solar Inverter Quantity Calculator
Works inverter quantities, where the architecture decides the count.
Result
Module-level electronics cost more up front and are usually required by rapid-shutdown rules in many jurisdictions. They also handle partial shading far better, because one shaded panel no longer drags a whole string down. A string inverter is simpler and cheaper on an unshaded roof with a single plane.
Get a Free Business AuditHow the calculation works
The array size and configuration converted into a count of string inverters, or into module-level units where microinverters or optimisers are used. The architecture choice drives both the count and the cost structure, and it is a design decision rather than an arithmetic one.
What moves the number
- Array size and the inverter capacity chosen.
- Architecture: string, optimised string, or microinverter.
- Number of roof planes and orientations.
- Shading, which favours module-level electronics.
Where this one goes wrong
Multiple orientations and partial shading are what justify module-level electronics, because a string inverter ties the modules in a string together and the weakest conditions affect the group. Where the roof is a single unshaded plane, the simpler and cheaper string architecture is frequently the better engineering. Any additional components priced per module should also be quoted as inputs rather than assumed, since prices move and a stale figure misprices the job.
Before you quote
- Choose the architecture from the roof, not from habit.
- Use current component prices rather than carried-forward figures.
- Count the inverter inputs available against the string count.
Questions
About this calculator
When are microinverters or optimisers worth it?
With multiple roof orientations or partial shading, because a string inverter ties modules in a string together and the weakest conditions affect the group. On a single unshaded plane the simpler string architecture is frequently better engineering.
How many string inverters does an array need?
Enough capacity for the array at the chosen DC to AC ratio, with enough inputs for the strings. Both have to be satisfied, and an inverter with sufficient capacity but too few inputs forces either combiners or a different unit.
Should component prices be assumed?
No, they should be entered from current quotes. Prices for modules, inverters and module-level electronics move enough that a figure carried forward from a previous job misprices the current one, usually in the installer's disfavour.
The formula
string inverters = AC capacity needed / inverter rating; microinverters = one per panel
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How to use this calculator
- System size (kW DC). Enter your own figure; the page starts at 7.2.
- Inverter capacity (watts AC). Enter your own figure; the page starts at 7,600.
- Spares and breakage (%). Enter your own figure; the page starts at 0%.
- Cost per inverter ($). Enter your own figure; the page starts at $1,650.
- Equipment type. Enter your own figure; the page starts at String inverter.
- DC to AC ratio. Enter your own figure; the page starts at 1.2.
The result updates as you type, so you can try a figure, see what it does to inverters, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| System size (kW DC) | 7.2 |
| Inverter capacity (watts AC) | 7,600 |
| Spares and breakage | 0% |
| Cost per inverter | $1,650 |
| Equipment type | String inverter |
| DC to AC ratio | 1.2 |
What comes out
| Result | Value |
|---|---|
| Inverters main result | 1 |
| Before rounding | 0.8 |
| Material cost | $1,650 |
| Cost per kW | $229.17 |
1 string inverter(s) to cover 6,000 W AC, about $1,650.
How sensitive the answer is
Holding everything else steady and changing only cost per inverter, this is what happens to inverters. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Cost per inverter ($) | Inverters |
|---|---|
| $825 | 1 |
| $1,238 | 1 |
| $1,650 example above | 1 |
| $2,475 | 1 |
| $3,300 | 1 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- System size (kW DC)
- A number, between 0 and 5000, starting at 7.2.
- Inverter capacity (watts AC)
- A number, between 0 and 100000, starting at 7,600.
- Spares and breakage (%)
- A percentage, between 0 and 25, starting at 0%.
- Cost per inverter ($)
- A money amount, starting at $1,650.
- Equipment type
- Choose from String inverter, Microinverter, one per panel, Optimisers plus one string inverter.
- DC to AC ratio
- A number, between 0.8 and 1.6, starting at 1.2.
What the results tell you
| Result | What it is |
|---|---|
| Inverters | The headline result. A number. |
| Before rounding | A decimal figure. |
| Material cost | A money figure. |
| Cost per kW | A money figure. |
A design still needs a site visit
Output and sizing figures use the assumptions you enter, not measured irradiance, shading or roof orientation at your address. Real production depends on all three, plus inverter behaviour and local interconnection rules.
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