Key takeaways
- The inverter location is a building decision as much as an electrical one, because heat, moisture and access decide how long the unit lasts.
- Follow the manufacturer’s clearance and ventilation requirements before you look at the wall, and never accept a mounting point where those clearances cannot be kept.
- Keep the DC string cables as short and as protected as the roof layout allows, and seal every point where they pass through the building envelope.
- Treat the AC connection and the switchboard as one design, with isolators that a service person can reach without moving anything else.
- Record the inverter position, the cable routes and the isolation points in the handover file, because the next person to touch the system will need them.
An inverter tends to be treated as a box that turns up on the plan late in the job. The solar installer arrives, looks for a wall that is close to the switchboard, and bolts the unit up where the cables happen to land. That is how a unit ends up in a hot roof void, under a bathroom exhaust, or in a laundry corner where the washing machine gets pushed against it every week and nobody looks at the screen again.
From the builder’s side, the inverter position sits where several things you already control meet: the roof, the framing, the switchboard, the wall finishes and the client’s daily use of the house. Get the location wrong and the cost arrives later. It shows up as a warranty callout for a unit that overheated, as a variation to re-route a cable that was never going to fit, or as a client who cannot reach the isolator without moving the furniture first.
This article is about placing the inverter and running its cables. It does not cover the roof frame, which is dealt with in the structural checks for rooftop solar frames article, or the sizing of a battery that might be added later. The question here is narrower: where does the box go, and how do the cables get from the array to the box and from the box to the switchboard, safely and in a way that can be found again when somebody needs to work on them?
Start with the path the power takes
Before anyone chooses a wall, trace the electrical path. The panels on the roof produce direct current. The inverter converts that into alternating current the house can use, and the converted power then leaves through the switchboard to the circuits and, when the system is connected, to the grid. Each leg of that path has its own cable type, its own protection and its own rules, and the inverter sits in the middle of the chain.
The practical consequence is that the inverter should be close to the switchboard, because that is where the AC output finishes, and as close to the array as the other constraints allow, because the DC run is the longer and more exposed leg. Those two pulls usually have a sensible midpoint, but it is rarely the spot an installer would choose if left alone with the drawing. Walk the route on site with the roof plan in hand before anyone drills a hole.
Ask the installer for the string layout, not just the panel count. The way the panels are grouped into strings sets how many DC runs leave the roof and where they enter the building. Strings on one side of the roof and strings on the other mean two separate entry routes, and the wall you choose has to accommodate both without the cables crossing each other or dropping across a door opening.
Heat, ventilation and the manufacturer’s clearances
An inverter produces heat when it works, and it loses efficiency and life when it cannot shed that heat. Most manufacturers publish a clearance zone around the unit, on the sides, above and below, along with a ventilation condition the space must meet. The rule for the builder is simple. The clearances in the installation manual are the minimum, not a target, and the wall you want must be able to meet them without an improvised modification that the installer would have to explain to the manufacturer later.
Avoid spaces that trap heat. A roof void, a sealed cupboard, or a garage with the roller door shut through the working day are all common mistakes. The unit is designed to work in the ambient temperature of the place it is mounted, and in the hot months of a NSW summer those enclosed spaces can run far above the outdoor air. A wall that takes the afternoon sun on its western face is another poor choice, because the unit is then heated from outside as well as from within.
The symptom of a badly placed unit is usually a loss of output on the hottest days. The unit is not faulty. It is protecting itself by reducing power, and the client will see the lost generation on the monitoring app without knowing why. When that conversation happens, it is much easier if the builder can point to the placement decision that was made on the walk-through and the clearance the manual called for.
Mounting height matters too. Keep the unit off the floor, where it is exposed to knocks from a trolley and to water from a mop or a hose, and high enough that the display and the isolator can be read and reached without a ladder. A location that needs a ladder just to see the screen will not have its screen checked, and a fault light that nobody sees is a fault that runs for months before anybody calls.
Placement checks before the wall is chosen
- Confirm the clearance zone and ventilation condition in the manufacturer’s installation manual.
- Check the space for heat sources, afternoon sun and any enclosed cavity that traps warm air.
- Confirm the mounting height keeps the display and the isolator reachable without a ladder.
- Check the flood information the council holds for the block and the drainage around the wall.
- Confirm the wall can carry the unit and its fixings, with the right anchors for the substrate.
- Ask the client about the room on the other side of the wall and their habits around the unit.
Keeping it dry: damp, flood and the low spot
Water is the other enemy. An inverter is an enclosed electronic device with a cover and cable glands, rated for the environment its enclosure protection describes. Indoors that rating still matters in a laundry, in a garage that takes water through the door after a storm, or in a space that shares a wall with a shower. Outdoors the rating has to match the exposure: direct rain, splash off the eaves, and the wind-driven spray that comes off a driveway after a car has been washed.
Flood is the case that planning documents take seriously. The NSW flood risk management manual sets out how land liable to flooding is assessed and managed, and the flood information a council holds for a block will show whether the land is affected in a larger event. A builder working on a site near a creek, on a low-lying street, or beside a floodway should check that information before choosing a wall. An inverter mounted below the level that the flood information identifies, even inside a garage, is a unit that will be submerged in the first serious event, and the insurance claim and the client conversation that follow are expensive for everyone involved.
Routing the DC cables from the roof to the wall
The DC string cables carry the most risk on the job. They run across the roof, through the roof or down a wall, and they carry the full output of the array at a voltage that can injure a person or start a fire if the insulation is damaged or a connector is badly made. Electrical safety is the first concern for anyone handling them, and the Safe Work Australia guidance on electrical safety describes the general hazards to plan for whenever people work near live equipment.
Keep each route short, fixed and protected. Keep the runs out of direct sun where the layout allows, because ultraviolet light degrades cable sheathing over time, and protect the cable from mechanical damage at every point where it passes a sharp edge, a fixing, a roof batten or a lid. Use the conduit and the cable management the installer’s design calls for, and do not allow a loose run to hang across a ceiling space where a future trade will catch it with a tool or a bundle of ducting.
Avoid long concealed runs that nobody can reach later. A cable buried in a wall cavity with no access point is a problem for the next electrician who needs to trace a fault, and it is a problem for the builder if the wall has to be opened for an unrelated repair. Where a concealed run is unavoidable, record the route on the as-built drawing and mark its position on the wall with a note in the handover pack.
Where a cable passes through the building envelope, seal the penetration to the same standard as the rest of the roof or wall. An unsealed hole for a DC cable is a water path, a pest path and an air leak as well as an electrical hazard. The sealant or the flashing should be the one the roof and wall systems call for, not whatever tube happened to be in the installer’s van.
The penetration nobody sealed. The mistake that costs the most is a DC run that is fixed to the outside of the roof sheeting with no weather seal where it passes through, or a run that loops back on itself so the installer can make it reach. Water finds the gap, the insulation degrades slowly, and nobody is monitoring the cable until the inverter starts to fault.
Routing the DC run from the roof to the building
- 1Trace the route on the roof planWalk the path from each string to the chosen wall before any hole is drilled.
- 2Protect the run from sun and damageFix the cable clear of sharp edges, fixings and foot traffic, in the conduit the design calls for.
- 3Seal each penetrationUse the sealing and flashing the roof and wall systems call for, and check it before the roof is closed.
- 4Label both endsMark each string at the inverter and at the array so a later electrician can trace it without guessing.
- 5Record the as-built routeUpdate the drawing with the actual route and any concealed section, and file it with the handover pack.
Running the AC side to the switchboard
On the AC side the cable runs from the inverter to the switchboard. The switchboard is where protection, isolation and the connection to the network come together, and it is where the installer’s design is tested most closely. Ask the installer to show you the arrangement on the drawing before the cable is pulled, because the requirements for connecting a generating system to the network, and the labelling of the switchboard, depend on how the circuits are laid out.
Keep the AC run short and take a sensible route to the board. Where the switchboard sits in a cupboard that is already full, the installer may need a larger enclosure or a rearrangement of existing circuits. That is a variation conversation with the client, not a detail to be solved at the end of the day by squeezing wires in. Price it, agree it in writing and then do it properly.
Isolation and the service visit nobody plans for
An inverter will need servicing. Sometimes the work is a firmware update, sometimes a replacement after a surge or a failed fan, and sometimes a fault that the monitoring points to. Whoever does the work has to isolate both the DC side and the AC side, and they have to do it without disturbing the rest of the house or working in a space that is unsafe to stand in. The isolators should sit where that person can reach them, clearly labelled, and not behind the very unit they are meant to switch off.
Plan the work space too. A unit mounted above a bench, a washing machine or a bed frame forces the service person to move things before they can do anything, and that makes the job slower and more expensive for the client. Leave room in front of the unit for a tradesperson to stand, kneel and open the cover, and keep the area clear of stored goods. Where a battery is also installed, the same principle applies, and the builder’s role in home battery installation is set out in its own article.
Noise, heat and the room that shares the wall
Inverters make a sound, especially some models under load, and a fan-cooled unit can be audible in a quiet room. A unit mounted on the wall of a bedroom, a study or a home office will be noticed by the people who sleep or work there. Where practical, mount it on a wall shared with a garage, a laundry or a corridor, and avoid a light internal partition that carries the sound straight through into the bedroom.
A worked example: the garage that looked right on the plan
Consider a builder in western Sydney finishing a double-storey house with a rooftop array on the rear slope. The installer’s first proposal put the inverter on the internal wall of the double garage, close to the switchboard and neatly out of sight. On the plan the location looked ideal, and the DC run from the rear roof was short enough that nobody questioned it.
On the site walk the builder asked three questions. The garage door stayed closed for most of the working day, so where would the heat go? The block sat on a low part of the street that the council flood information showed as affected in a larger event, so what was the risk to a unit mounted at the height the installer had picked? And the only spare wall space left the unit touching a shelf that the owner planned to use for paint tins, so could it keep its clearances at all?
None of those answers appeared on the electrician’s plan. The solution was to move the inverter to an external wall on the side of the house that stayed in shade through the afternoon, mount it above the level the flood information identified, use a suitably rated enclosure, and keep the clearance zone free of storage. The DC run grew by a modest length, and the builder had the extra cable routed in a protected channel with a sealed penetration. The job cost a little more, the variation was agreed in writing before the work started, and the client has not had to think about the unit since.
The lesson is not that a garage is always wrong. It is that a location chosen from the plan alone has not been tested against heat, water, access and the owner’s use of the space, and each of those is a question the builder can answer on the walk-through, before the first hole is drilled.
Recording the layout for the handover and the certifier
Once the install is finished, the record matters as much as the wiring. The handover pack should show where the inverter is mounted, which isolators control what, the route of each DC and AC run in a form that someone can follow later, and each penetration that was sealed and how. Keep the commissioning sheets, the network connection paperwork and the manufacturer’s clearance requirements with the rest of the building file, so that a future electrician or a certifier can see what was done without taking the wall apart.
Note the monitoring details and the warranty registration for the unit, and make sure the client knows who to call for a fault. A missing contact is how a small fault becomes a dispute about who is responsible for it. The PointCPD guide to how NSW builder CPD works explains how the same documentation habits feed into a builder’s professional development, and the course catalogue lists the modules that cover electrical responsibilities from the builder’s side.
Putting the location in the contract
The contract should say who is responsible for the inverter location, the cable routes and any variation that follows from a site walk. The NSW Government guidance on contracts for home building work is a useful reference for what a written agreement should cover, and the builder should not leave the inverter position as an open point on the drawing. Record the chosen location, the cable routes and any agreed change in writing, with the client’s signature, before the installer starts work.
Questions builders ask
Can an inverter go in the garage?
It can, but only if the garage keeps the clearances and ventilation the manufacturer requires and does not trap heat while the door is closed. Check the flood information for the block and whether the garage takes water in a storm. A garage is a common choice that often needs a closer look than it first appears to deserve.
Should the inverter be near the switchboard?
Usually the inverter should be close to the switchboard, because that keeps the AC run short and the connection simple. The DC run from the roof is the longer and more exposed leg, so the final position is a balance between the two. Walk the route on site before deciding.
What clearances does an inverter need?
Each manufacturer sets its own clearance zone and ventilation condition, and those are written in the installation manual for the specific model. Treat them as the minimum, not a target. If the wall cannot meet them without an improvised change, choose another wall.
How should DC cables be routed on a roof?
Keep each run short, fixed and protected from sun and mechanical damage, and use the conduit and cable management the installer’s design calls for. Seal every penetration to the standard of the roof or wall system. Record the route so it can be found again.
Who is responsible for sealing the cable penetrations?
The scope should be written into the installer’s agreement and the contract with the client. Penetration sealing is one of the items most often missed when the crew leaves the site. Make it an explicit line item, and check it before the roof is closed.
What should go in the handover pack for an inverter?
Include the inverter location, what each isolator controls, the as-built route of each DC and AC run, the sealed penetrations, the commissioning sheets, the network connection paperwork and the manufacturer’s clearance requirements. Add the monitoring details and a contact for faults.
Sources
- Electrical safety · Safe Work Australia
- Continuing professional development for builders and swimming pool builders · NSW Government
- General building work licensing · NSW Government
Published 17 October 2026. General information for builders, not legal, financial or engineering advice for a specific job. Check current requirements with the relevant regulator or standard before relying on them.
