Quick answer
String Inverter A string inverter is a single wall-mounted inverter that converts the DC output of one or more strings of series-wired solar panels into AC for the home.
Because the panels in a string share one current, the string runs at a single operating point. That keeps the hardware simple and in one place you can service, but lets one shaded or weaker panel drag down its neighbours.
Quick facts
The key facts about string inverter, with sources:
- Wiring
- Panels in series (a string); one or more strings per inverter 1
- Location
- One box, usually near the main electrical panel or meter
- Residential sizes (one product line)
- 3,000–11,400 VA AC (SolarEdge HD-Wave, single phase) 3
- Published CEC efficiency (example)
- 99% at 240 V, SolarEdge HD-Wave 3
- Main limitation
- Shade or mismatch on one panel affects the whole string 1
- Often paired with
- Power optimizers for panel-level tracking and rapid shutdown 3
- Replacement
- DOE expects at least one inverter replacement in a 25-year array life 2
Key takeaways
- A string inverter turns a whole row of panels into AC in one box on the wall.
- Panels in a string share one current, so shade on one panel costs the whole string.
- It suits sunny roofs with one or two faces and few obstacles.
- Some string inverters only work with power optimizers behind each panel.
- One box is easy to reach and replace, but if it fails, the whole array stops.
What a string inverter is
A string is a row of panels wired end to end. A string inverter takes one or more of these rows and turns their DC into AC for the house. The DOE puts it simply: the inverter converts the power made by the entire string 1.
It is the oldest and most common layout on homes. The DOE notes that a single inverter is generally cheaper and is easier to cool and service than one inverter per panel 2. The trade-off is how it handles shade, which the next section explains.
How a string works
Wiring panels in series is like linking batteries end to end. The voltages add up, and the same current passes through every panel. Ten panels at about 40 volts each make a string of a few hundred volts. The SolarEdge HD-Wave inverter, for example, takes up to 480 volts DC 3.
The catch is the shared current. If a chimney shadow cuts one panel’s current, the string either runs at that lower current, or the panel’s bypass diodes switch part of it out.
Either way, healthy panels give up some output. The DOE says this setup lowers production on the string if any single panel has a problem such as shade 1.
A string inverter finds the best operating point with a maximum power point tracker on each input. Many models have two or more inputs. Panels on two roof faces can then sit on separate strings, rather than sharing one compromise point.
The path from a string to your outlets
- Panels wired in series → one high-voltage DC string → DC disconnect
- String inverter → tracks the string’s best point → converts DC to AC
- AC → main electrical panel → home circuits → meter → grid
Kinds of string inverter
| Kind | Who tracks each panel | What you get | Example |
|---|---|---|---|
| Plain string inverter | The inverter tracks the whole string | Fewest parts; shade costs the string | Sold by several makers |
| String inverter with optimizers | An optimizer behind each panel | Panel-level tracking and data; one inverter | SolarEdge HD-Wave, built only for optimizers 3 |
| Hybrid string inverter | The inverter, per input | Also charges and runs a battery | Tesla Powerwall 3, six inputs 5 |
| Three-phase string inverter | The inverter, per input | For commercial buildings with three-phase power | Not used on most US homes |
Example: reading a string inverter data sheet
| Row | SE7600H-US value | What it tells you |
|---|---|---|
| Rated AC power output | 7,600 VA | The most it will deliver. Above this it clips. |
| Maximum DC power @240V | 11,800 W | How much panel DC it accepts: about 155% of AC. That is the ceiling on the DC-to-AC ratio. |
| Maximum input voltage | 480 V DC | The string must stay below this, even on the coldest morning. |
| Number of strings | 1–2 (smaller units) or 1–3 (larger units) | How many rows of panels it can take. |
| Maximum inverter efficiency | 99.2% | Best single point. Not the number to compare. |
| CEC weighted efficiency | 99% @ 240 V; 98.5% @ 208 V | The comparison number. See inverter efficiency. |
| Grid connection standards | IEEE 1547, Rule 21, Rule 14 (HI) | Which utility rules it is certified to. |
Where you find a string inverter
On the house, look for a grey or white box on an outside wall, in a garage or near the main panel. It often has a DC safety switch on the side or underneath. Conduit runs from it up to the roof.
On a quote, it appears as a brand, a model number and an AC size, such as 7.6 kW. That AC size matters for your utility. Georgia Power’s application, for example, asks for the total inverter nameplate in kW AC and the panel total in kW DC 8.
In your app, a plain string inverter shows one total for each string. You will not see each panel unless optimizers are fitted.
Sources: [8]
Strengths and weaknesses
What it does well
Where it falls short
- Shade, dirt or a failed panel cuts the whole string.
- A single failure stops the whole array until it is fixed.
- Panel-level data and module-level shutdown need extra parts.
- Adding panels later must fit the string’s voltage window.
Limits to know before you choose one
Shade is the big one. On a roof with trees, vents or dormers, a plain string loses more than it needs to. Our guide to shade and solar output shows how much.
Mixed roof faces are a second limit. Each face needs its own input. If the inverter has too few, two faces share one compromise point.
Heat is a third. The HD-Wave sheet promises full power only up to at least 50 °C. Above that, the inverter may reduce output to protect itself 3. Mount it out of strong afternoon sun where the manual allows.
Cost drivers, lifespan and warranty
We do not print a price, because quotes vary. The cost drivers are the AC size, the brand, whether optimizers are needed, and how far the box sits from the main panel.
One inverter for the whole roof is often the lower-cost layout, the DOE notes 2. See our cost per watt guide to compare quotes.
Plan for a replacement. The DOE expects inverters to be replaced at least once in a 25-year array life 2. The HD-Wave sheet prints a 12–25 year warranty 3. Ask which term applies to your quote and what labor it covers.
How a string system is designed and installed
A licensed installer and electrician do every step. This is what to expect.
- The designer counts panels per string from the panel voltage, the inverter’s voltage window and the coldest local temperature.
- They group panels by roof face so each face has its own input.
- They check the DC-to-AC ratio against the data sheet limit.
- The installer gets a building and electrical permit and applies to the utility.
- A licensed electrician mounts the inverter, runs conduit to the roof and wires disconnects.
- An inspector checks the work, then the utility gives permission to operate.
See permission to operate for the last step.
Keeping a string inverter healthy
Watch the app. A plain string inverter cannot tell you which panel is weak, so compare each string’s output month to month. If one string falls behind the other, ask for a test.
Keep the box clear. Do not stack items against it or block its vents. Keep plants trimmed back so air can flow.
Book a check if output drops and there is no new shade. Our solar repair page covers what a technician tests.
Warning signs and when to call a pro
Call your installer or a licensed electrician if you see any of these. Do not open the inverter or the DC switch box.
- Zero output on a sunny day.
- One string far below the other with no new shade.
- An error code or red light that does not clear.
- Burning smell, scorch marks or buzzing near the box.
- The inverter shuts off every hot afternoon.
Safety rule
A string can carry hundreds of volts of DC whenever light hits the panels. Only a licensed electrician or installer should work on it.
Rules a string inverter must meet
A grid-tied string inverter must be listed to UL 1741 and follow IEEE 1547. The current edition, IEEE 1547-2018, was published on 6 April 2018 6. To appear on the California Energy Commission list with Supplement SB, a maker must use UL 1741 3rd Edition and show it meets IEEE 1547-2018 7.
The National Electrical Code (NEC) adds fire-safety rules. The HD-Wave sheet lists arc-fault protection and rapid shutdown under NEC 2014, 2017 and 2020, articles 690.11 and 690.12 3. Article 690.11 covers arc faults, which are sparks in DC wiring. Article 690.12 covers rapid shutdown, which drops roof voltage for firefighters.
Your city or county adopts a code edition, and the inspector decides how a roof meets it. Ask which edition your permit uses.
String inverters with optimizers and rapid shutdown
Some string inverters only work with a power optimizer behind each panel. SolarEdge’s HD-Wave line is one. Its sheet says it is “specifically designed to work with power optimizers” and calls it a fixed-voltage inverter 3.
This layout keeps one central inverter but adds panel-level tracking and data. When shut down, each optimizer drops to a safety voltage of 1 volt 4. That is one way designs meet the rapid-shutdown rule.
String inverter vs microinverters and optimizers
| Your roof | Plain string inverter | Better fit |
|---|---|---|
| One or two unshaded faces, all panels the same | Good fit: fewest parts, one box to service | — |
| Faces pointing three or more ways | Needs an MPPT input per face; check the count | Microinverters or optimizers |
| Trees, vents or dormers shading some panels | Shade on one panel costs the whole string | Power optimizers or microinverters |
| Battery planned now or later | Battery added with its own inverter | A hybrid inverter |
| Array likely to grow | New panels must match the string design | Ask how expansion would be wired |
Misconceptions
- Myth String inverters are outdated.
- Reality They are still widely sold and print some of the highest efficiencies, such as 99% CEC on HD-Wave 3. The roof decides, not the age of the idea.
- Myth Any shade shuts the whole string down.
- Reality Bypass diodes let a shaded panel be partly skipped. The string loses output but keeps working.
- Myth A bigger string inverter is always safer.
- Reality An oversized inverter runs at low load most of the day, where efficiency is lower. Most designs put more DC on the inverter than its AC rating.
String inverters in SC, GA and VA
Utilities in these states set size caps in AC, which is the inverter’s rating.
Dominion Energy South Carolina’s Solar Choice rider 10 and Duke Energy Carolinas’ Rider RSC 11 both cap residential systems at 20 kW AC.
In SC, wiring and connection need a residential builder, a licensed residential electrician or a mechanical contractor with the electrical classification 12.
Georgia Power asks for inverter spec sheets showing UL1741SB and IEEE1547-2018 8. Virginia requires systems to meet NEC, IEEE and testing-lab standards 9.
Is a string inverter right for you?
A string inverter is a strong choice when most of these are true:
- Your panels face one or two directions.
- Little or no shade falls on the panels between 9 a.m. and 3 p.m.
- You want the fewest parts on the roof.
- You are fine seeing output by string, not by panel.
- If a battery is planned, ask whether a hybrid model makes more sense now.
Related guides and tools
Questions about string inverter
Is a string inverter better than microinverters?
Neither is better everywhere. A string inverter suits a sunny roof with one or two faces. It keeps all the electronics in one box you can reach. Microinverters or optimizers suit roofs with part shade or several faces. They cost more parts on the roof. Ask your installer to model both on your roof.
How many panels can go on a string inverter?
It depends on the panel voltage and the inverter’s input voltage window. Both are on the data sheets. The count is also adjusted for the coldest local temperature, since cold raises panel voltage. The installer’s string calculation sets it. There is no single number that fits every roof.
What happens if one panel in a string fails?
The string’s output drops. Depending on the fault, the inverter may stop making power from that string. A plain string system shows only that output fell, not which panel failed. A technician then has to test the string. Optimizers or microinverters show the exact panel.
Can a string inverter work with a battery?
A standard grid-tied string inverter cannot charge a battery directly. The battery is added with its own inverter on the AC side, which is called AC coupling. A hybrid inverter is a string-type inverter that also runs a battery. It is often the simpler choice if you plan storage from the start.
How long does a string inverter last?
Makers print warranties, not lifespans. The SolarEdge HD-Wave sheet prints a 12–25 year warranty. The DOE expects an inverter to be replaced at least once in a 25-year array life. Read the warranty on your quote and ask whether it covers labor.
Where is a string inverter installed?
Usually on an outside wall, in a garage, or near the main electrical panel. The spot must follow the maker’s manual and the local code. Shade helps, since heat can make the inverter cut output. A licensed electrician mounts and wires it.
Do string inverters work in partial shade?
Yes, but they lose more than panel-level systems. Shade on one panel lowers the shared current of the whole string. Bypass diodes limit the loss. If more than a few panels see shade, optimizers or microinverters usually recover more energy.
Can I add panels to a string inverter later?
Sometimes. The new panels must fit the string voltage window and the inverter’s DC limit. Matching older panels can be hard. It usually needs a permit revision and a utility notice. Ask a licensed installer to check first.
Sources
- US Department of Energy, Solar Integration: Inverters and Grid Services Basics, retrieved .
- US Department of Energy, Solar Photovoltaic System Design Basics, retrieved .
- SolarEdge, Single Phase Inverter with HD-Wave Technology for North America data sheet (12/2020/V01, distributor-hosted copy), retrieved .
- SolarEdge, Power Optimizer S440 / S500 / S500B data sheet (DS-000091-ENG, 8 Nov 2022, government-hosted copy), retrieved .
- Tesla, Powerwall 3 Datasheet (2024), retrieved .
- IEEE Standards Association, IEEE 1547-2018, retrieved .
- California Energy Commission, Inverter Listing Request Instructions (rev. 26 Aug 2025), retrieved .
- Georgia Power, Behind-the-Meter Interconnection Summary for Residential Customers (rev. 15 Aug 2025), retrieved .
- Code of Virginia §56-594 (net energy metering), retrieved .
- Dominion Energy South Carolina, Residential Solar Choice rider (Rider to Rate 5), retrieved .
- Duke Energy Carolinas (SC), Rider RSC Residential Solar Choice, retrieved .
- SC LLR, Residential Specialty Contractor registration (Solar Panel Installer), retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Mechanism from the DOE inverter and system-design primers; every number copied from the named SolarEdge and Tesla data sheet revisions; standards from the IEEE 1547-2018 listing and CEC instructions; state facts from sc-local/facts.js, the Georgia Power summary and Va.
Code §56-594. The fit table is HyreSolar’s judgement from those mechanisms, not a maker claim.
Suggest a correction. We fix errors and say what changed.