Panels get the attention. The inverter decides what you actually receive. It converts DC to AC, tracks the array's optimum operating point moment by moment, protects the system, reports what it's doing — and it is the one component almost certain to be replaced once during the plant's life. Choosing it well is worth more than an extra ten watts per panel.
On this page
What an inverter actually does
Four jobs, in descending order of how often they're discussed and ascending order of how much they matter.
- Conversion. Panels produce DC; your building and the grid use AC.
- Maximum power point tracking (MPPT). A panel's optimum voltage shifts constantly with sunlight and temperature. The inverter hunts for that point many times a second. Bad tracking loses real energy on cloudy days.
- Protection and grid compliance. Anti-islanding (disconnecting during an outage so line workers aren't electrocuted by your rooftop), earth-fault detection, surge handling.
- Monitoring. The only window you have into whether the plant is healthy — see our maintenance checklist.
The one fact to carry away
Panels are warranted for 25 years and typically hold around 80–85% of rated output at year 25. Inverters typically last 8–12 years. Any financial model that doesn't budget for one inverter replacement is not conservative — it's incomplete. Our payback calculator lets you account for it.
The four types, compared
| Type | How it works | Best for | Trade-off |
|---|---|---|---|
| String inverter | One inverter serves a series "string" of panels | Clear, uniform, unshaded roofs | One shaded panel affects the whole string |
| Microinverter | A small inverter under each panel | Shaded or multi-orientation roofs | Higher cost; more units on the roof |
| Power optimiser | Per-panel electronics feeding one string inverter | Partial shading, panel-level monitoring | Middle cost; still one central failure point |
| Hybrid inverter | String inverter with battery + backup capability | Homes and sites wanting outage backup | Costs more; needs a battery to be useful |
There is no universally correct answer. There are two questions that decide it, and both are about your site rather than the product.
Shading: the deciding factor
A conventional string behaves somewhat like a single pipe: constrict it anywhere and you throttle the whole flow. Panels wired in series carry the same current, so the weakest module in the string sets the pace for all of them.
The consequence catches people out. A row of bird droppings across one module, a water tank's shadow crossing two panels at 4pm, a neighbour's new parapet — each can cost more generation than the affected surface area would suggest, because the loss propagates along the string.
Where module-level electronics earn their premium
If your roof has unavoidable partial shading — a tank, a stairwell head, a tree you won't cut, a chimney — or if panels must face more than one direction, microinverters or optimisers stop one compromised module from dragging down its neighbours. On a genuinely clear, single-orientation roof, they are an expense without a return.
They also give panel-level monitoring. On a large array, knowing which module is underperforming — rather than that total output is down 4% — turns a day of fault-finding into a ten-minute fix.
If you want power during cuts
This is the point most often misunderstood, so plainly:
A standard grid-tied solar system shuts down during a power cut. Not because of a fault — by design. If the grid is dead and your rooftop kept exporting, a line worker repairing the fault could be electrocuted. Every compliant inverter includes anti-islanding protection that disconnects the moment the grid drops.
Sunshine on your roof and no power in your house is the expected behaviour of a grid-tied system.
To ride through outages you need both:
- A hybrid inverter (or a backup-capable inverter with a dedicated backup output), and
- A battery, sized to the loads you want to keep alive.
A hybrid inverter without a battery provides no backup. It merely leaves you ready to add one later — which can be a reasonable choice if you expect to.
When storage is warranted, lithium (LFP) is the sensible default: longer cycle life, far higher usable depth of discharge, compact and low-maintenance. Lead-acid costs less to buy and considerably more per usable unit across its life — you need roughly double the rated capacity for the same backup. Size it honestly with our battery backup estimator, which shows both side by side.
Sizing and DC:AC ratio
Your array is rated in kWp (DC). Your inverter is rated in kW (AC). They are not required to match, and usually shouldn't.
Panels almost never produce their rated peak. Rated output is measured under standard test conditions — bright, cool, perpendicular light — which a Madurai afternoon in May does not resemble, because heat reduces efficiency. Consequently a modest oversizing of the DC array relative to the inverter is normal and beneficial: it lifts output through mornings, evenings and cloudy periods, when the array would otherwise sit well below the inverter's capability.
Push it too far and you get clipping: on the brightest hours of the best days, the array produces more than the inverter can pass, and the excess is simply lost.
| DC:AC ratio | Effect |
|---|---|
| Around 1.0 (matched) | Inverter underused most of the day; more capital in the inverter than needed |
| Modestly above 1.0 | Usual design choice — better shoulder-hour output, negligible clipping |
| Aggressively above 1.0 | Noticeable clipping at midday; energy discarded |
The right ratio depends on your latitude, orientation, and — for businesses — whether your load peaks at midday anyway. Ask your designer what ratio they've used and why. A designer who hasn't thought about it will not have an answer.
MPPTs, explained plainly
An MPPT is an independent tracking channel. Panels connected to the same MPPT are optimised together, as a group.
That's fine when they experience the same conditions. It's a problem when they don't:
- Multiple orientations. East-facing and west-facing panels peak at different times. On one MPPT, the tracker compromises between them and both underperform. On separate MPPTs, each is optimised on its own terms.
- Uneven shading. One string shaded in the afternoon, another clear. Separate MPPTs prevent one from dragging the other down.
- Different string lengths, which arise naturally on irregular roofs.
So: a simple, single-orientation, unshaded roof can be served by one MPPT. A real roof, with a tank and two faces and a stairwell, usually wants two or more. This is a design question, and it should be answered in your single-line diagram before anyone orders anything — see our EPC process guide on why the design gate matters.
Specifications that matter
Cutting through the datasheet:
| Specification | Why you care |
|---|---|
| Rated AC output (kW) | The ceiling on what reaches your building |
| Number of MPPTs | Whether your roof's complexity is handled properly |
| Maximum DC input voltage & current | Constrains string design; must suit your layout |
| Peak and weighted efficiency | Weighted (real-world) matters more than the headline peak |
| Operating temperature range & derating | Critical in Madurai. An inverter that derates in heat loses you midday output |
| IP rating | Outdoor mounting needs proper ingress protection |
| Warranty term, and what's included | Labour and replacement, or the box only? |
| Monitoring & access | Do you get credentials, or only the vendor? |
| Local service presence | An unsupported brand is a stranded asset in year nine |
Two under-asked questions
"At what temperature does this inverter start derating, and by how much?" — a heat-sensitive inverter quietly surrenders exactly the midday hours you bought it for. And "Who services this brand in Tamil Nadu, and how quickly?" — a plant offline for three weeks in April has lost the best generation of its year.
A decision path
Four questions, in order. Answer them honestly about your site.
-
Do you need power during outages?
Yes → you need a hybrid inverter and a battery. Continue to question 2 for the array side.
No → a grid-tied inverter is sufficient. Don't pay for backup capability you won't use. -
Does any part of the array suffer unavoidable shading, at any
time of year?
Yes → microinverters or optimisers.
No → continue. -
Do panels face more than one direction?
Yes → at minimum a string inverter with separate MPPTs per orientation; module-level electronics if the split is complex.
No → continue. - Otherwise: a good string inverter, correctly sized, with adequate MPPTs and a serviceable brand. It is the right answer more often than the industry's marketing implies.
Note that price never appears in that sequence. Price decides which string inverter, or which microinverter. It should not decide the architecture — that's set by your roof.
Frequently asked questions
String inverter or microinverters?
String inverters suit clear, uniform, unshaded roofs and cost less. Microinverters and optimisers handle shading and multi-orientation roofs by optimising each panel individually, at higher cost. Your roof decides, not a general ranking.
Do I need a hybrid inverter?
Only if you want power during outages or plan to add storage. A standard grid-tied inverter shuts down during a power cut by design, for line-worker safety. A hybrid without a battery gives no backup.
How long does an inverter last?
Typically 8–12 years — the component most likely to be replaced once during a 25-year system life. Budget for it.
What is DC:AC ratio?
Installed panel capacity against inverter AC rating. Modest DC oversizing is normal and improves shoulder-hour output, since panels rarely hit their rated peak. Excessive oversizing causes clipping, where midday generation above the inverter's limit is lost.
How many MPPTs do I need?
One can serve a single-orientation, unshaded roof. Multiple orientations or uneven shading call for separate MPPTs, so one compromised string doesn't drag down the others.
Let's match the inverter to your roof.
We survey shading across the year, model string layouts, and specify inverters by make and model — never "branded inverter." Free site assessment in Madurai.