Choosing an Inverter for Solar Panels: The Four Rows That Decide

Type “inverter for solar panel” into a search box and you are not asking what an inverter is. You have panels, or a quotation for panels, and you want to know which box belongs behind them: how many of them it will accept, in how many strings, at what voltage, and how much current each of its trackers can stand. That is a relationship question rather than a product question, and it is answered by four rows on the inverter's spec record.

One thing before the rows, because it decides what this page may honestly claim: we do not sell solar panels. Our catalogue holds inverters, batteries and solar air conditioners — and not one of them is a panel. So this is not a bundle page. It is about choosing the inverter for panels you are buying somewhere else, which is the half of the decision that actually goes wrong.

We are an authorised Deye distributor, and every number below is copied off a spec record we publish. If you already have a panel datasheet and a roof count, send them on WhatsApp +971 4 255 0887 or by email to sales@deyeinverters.net and we will read the matching rows against them.

Only twelve of our records mention a panel at all

Of the 170 Deye spec records we publish, 134 are inverters, 34 are batteries and 2 are solar air conditioners. Across all of them there is exactly one column that names a panel — Supported PV Module Power — and it is stated on 12 records, the microinverters, as the per-module wattage window each unit is built around.

That is the entire panel content of our source. No other record states a panel wattage, and no record anywhere states a panel's open-circuit voltage, its temperature coefficient, its short-circuit current or its dimensions — Deye does not make panels, and we do not publish figures we do not hold. Everything below is the inverter's own limit, and the method is always the same: take the number off your panel's datasheet and read it against the row here.

Row one: how many watts of panels it will take

The first row is Max. PV Input Power, and it only becomes useful when you read it beside Rated AC Output Active Power on the same record. Not one of the 134 inverter records states those two as equal. Every single one is allowed more panel wattage on its input than it will ever deliver as AC, which is why “a 5 kW inverter needs 5 kW of panels” is the most common wrong answer in this category.

Counted across the range, 47 records state exactly 1.60× their rated AC output, 40 state 1.50× or a shade above, 12 state 1.40× or a shade above, and the remaining 35 sit between 1.30× and 1.36×. The narrowest headroom in the whole range belongs to SUN-2.7K-G04P1, which takes 3,500 W of panels on a 2,700 W rated output; the widest in absolute terms is SUN-136K-G01P3 at 204,000 W on 136,000 W.

On the 52 records that accept a battery — the 49 hybrids and the 3 off-grid units — there is a second, higher ceiling: Max. PV Access Power. It is stated on all 52 and on every one of them it is exactly twice the rated AC output. SUN-5K-SG04LP3 reads 5,000 W rated AC, 7,500 W max PV input, 10,000 W max PV access. SUN-50K-SG01HP3 reads 50,000 W, 80,000 W and 100,000 W on the same three rows.

The two rows are not in conflict; they answer different questions. The access figure is how much array may be wired onto the machine. The input figure is how much of it the trackers will process at once. On a battery machine the extra array is not wasted — it is what fills the battery in the shoulder hours while the AC side is already at its ceiling. On the 82 records without a battery there is only one figure, because there is nowhere for the surplus to go.

Row two: the voltage window, which is stricter than the wattage

Wattage is the row people quote. Voltage is the row that stops an installation from working. Four figures describe it on every record, and they are worth naming separately: Startup Voltage is the string voltage the machine needs before it will begin at all; MPPT Voltage Range is the window inside which it genuinely tracks; Rated PV Input Voltage is the point the design is centred on; and Max. PV Input Voltage is the absolute ceiling, above which the string must not be connected.

Read that table the way a commissioning engineer does, from both ends. Too few panels in a string and its voltage sits under the startup figure, so the machine will not wake up on a dull morning and the owner reports a fault that is not one. Too many, and the string's cold-morning open-circuit voltage crosses the maximum — the one limit on this page that damages hardware rather than merely disappointing it.

And here is a number we cannot give you. Your panel's open-circuit voltage, and how far it rises as the temperature falls, is printed on your panel's datasheet and appears nowhere in our records. So that half of the check is yours: take the panel's Voc at the coldest temperature your site sees, multiply by the number of panels in the string, and keep the answer below the Max. PV Input Voltage row above. We publish the ceiling. The panel maker publishes the figure that has to stay under it.

The width of the window is worth as much as its top. A record reading 200–850 V tracks across a 650 V span; one reading 25–55 V, the microinverter window, tracks across 30 V because it is designed around a single module rather than a string. The MPPT efficiency row reads greater than 99 % on all 134 records — but only inside that window, which is what makes the window the specification and not a footnote.

Row three: how many strings, and which tracker they land on

Two rows answer this together. Number of MPPTs is 2 on 83 records, 4 on 16, 1 on 15, 3 on 8, 6 on 7 and 8 on 5. Strings per MPPT then says how many strings each of those trackers accepts, written tracker by tracker with a plus between them: “1+1” on 49 records, “2+2” on 21, a bare “1” on 15, and up to “4+4+4+4+4+4+4+4” on the largest string inverters. Total string capacity across the range runs from 1 to 32.

Read the pluses rather than the total, because the trackers are not always equal. SUN-12K-SG04LP3 states 2+1 — two strings on the first tracker, one on the second — and the current row agrees with it at 26+13 A. Split a twelve-panel array evenly across those two inputs and you have designed for a machine that does not exist. The same asymmetry appears on 9 records in all — 5 string inverters and 4 hybrids, written as 2+1 or 1+2 — and it is invisible unless you read the notation.

Row four: current, stated per tracker and not per machine

The last two rows are Max. Operating PV Input Current and Max. Input Short-Circuit Current, and both are stated on all 134 records with the same plus notation, which means they are per tracker. The first is what the input is designed to carry in normal service. The second is what it is built to survive when a string is shorted, and it is always the larger of the two — 20+20 A against 30+30 A on SUN-8K-SG05LP3, 40 A against 60 A per tracker on SUN-70K-G03.

Here too the matching number belongs to your panel, not to us. A module's short-circuit current is on its datasheet; ours holds no panel currents at all. Parallel strings on one tracker add their current, so the check is the sum of the strings on that tracker against that tracker's segment of the row — not against the whole row, and not against the machine.

Hybrid solar power inverter, on-grid, off-grid: the array side barely moves

People search “hybrid solar power inverter”, “solar inverter on/off grid” and “solar inverter without battery” as though they were three different array problems. They are not. The four rows above are stated on all 134 records whatever the type, and a string of panels does not know which kind of machine is at the end of it. What changes is everything downstream of the trackers.

• The 70 string inverters are the on-grid case. They state zero-export support as Yes — the only 70 records that state it at all — and Not Applicable on battery type, AC coupling, generator support and charge/discharge periods.
• The 49 hybrids are the on-grid and off-grid case in one box. They state a battery type, AC coupling support as Yes, generator support as Yes (Diesel), and six programmable charge/discharge periods.
• The 3 off-grid units — SUN-3.6K-OG01LP1, SUN-5K-OG01LP1 and SUN-6K-OG01LP1 — state a battery type and are the only three records in the range whose arc-fault circuit interrupter reads Yes rather than Optional.
• The 12 microinverters sit under the panels instead of beside the meter. They are the only isolated topology in the range, the only records with no DC switch, and the only ones that name a panel wattage.

One honest note on that list: zero-export support reads Yes on the 70 string inverters and Not Stated on the other 64. Not Stated is not a No and we will not read it as one, but it is also not a figure we will publish as a capability.

The solar-inverter-without-a-battery case, in numbers

82 of the 134 records read Not Applicable on the battery row: the 70 string inverters and the 12 microinverters. The same 82 read Not Applicable on AC coupling, on generator support and on the charge/discharge period row, so choosing one is not choosing a machine with hidden battery settings — it is choosing a machine on which those rows do not exist.

What that buys is efficiency and array size. The highest maximum efficiency anywhere in the range, 98.8 %, is stated on 8 records and all 8 are string inverters; SUN-70K-G03 states 98.7 % maximum and 98.1 % European efficiency while accepting 91,000 W of panels across four trackers. What it costs is the second ceiling: with no battery there is no Max. PV Access Power row, so the array stops at 1.30× to 1.51× of rated output rather than 2×.

What every record guarantees on the DC side

Four rows describe the array connection itself, and they are worth checking before anyone buys a combiner box they do not need:

• DC reverse polarity protection reads Yes on all 134 records, and insulation impedance detection reads Yes on all 134 as well.
• A DC switch is stated on 122 records and Not Applicable on the 12 microinverters, which have no string to isolate.
• Surge protection reads Type II on both the DC and the AC side on 122 records, and Type II on the AC side only on the 12 microinverters.
• String monitoring is Optional on the 70 string inverters, Not Stated on 52 and Not Applicable on the 12 microinverters; an arc-fault circuit interrupter is Optional on 119 and Yes on the 3 off-grid units.

The order to do it in

Six steps, each one reading a row that exists rather than a rule of thumb:

1. Decide the AC output you need first, because every PV limit on the record is expressed against Rated AC Output Active Power.
2. Multiply that by the record's Max. PV Input Power ratio to get the array size the trackers will process — and if the machine takes a battery, note its Max. PV Access Power as the larger figure you may actually wire on.
3. Take your panel's cold Voc from its own datasheet, multiply by panels per string, and keep the result under Max. PV Input Voltage while keeping the warm-day string voltage above Startup Voltage and inside the MPPT Voltage Range.
4. Lay your strings out against Number of MPPTs and Strings per MPPT, reading the pluses separately — the trackers are not always the same size.
5. Add the short-circuit current of the strings on each tracker and compare it with that tracker's segment of Max. Input Short-Circuit Current.
6. Only then pick the type: string for a battery-free grid-tied array, hybrid for grid plus storage, off-grid where there is no grid, micro where the roof has more than one orientation.

If you would rather start from your own array than from the general rule, send the panel model and the number of panels and we will send back the records whose four rows fit them, with the figures exactly as the record holds them — on WhatsApp +971 4 255 0887 or at sales@deyeinverters.net.