What actually happens when you install solar — from site survey and permits to mounting, wiring, inspection and commissioning. Includes what drives installation cost, how to compare quotes, and the red flags that should end a sales conversation.
Buying solar panels is easy. Getting them installed properly is the part that determines whether your system quietly produces power for twenty-five years or becomes a recurring source of roof leaks, tripped breakers and warranty arguments.
Most homeowners approach this with almost no visibility into what the installer is actually doing up there. This guide fixes that. It walks through the complete installation process in order, explains what drives the price, shows you how to compare quotes on equal terms, and lists the red flags that should end a sales conversation immediately.
Before anything else: is your roof ready?
A solar array is a twenty-five year commitment bolted to a surface that may have less life left in it than that. Sort this out first, because removing and reinstalling an array to replace a roof underneath it is one of the most expensive avoidable costs in solar.
Check these before you take a single quote:
Remaining roof life. If your covering has fewer than about ten years left, replace it first. Many installers will refuse the job otherwise, and the ones who won't refuse are the ones you should worry about.
Structural capacity. A modern array adds roughly 12–20 kg per square metre. Most sound roofs handle this easily, but older timber, tile roofs with previous water damage, or long unsupported spans need a structural opinion.
Roof material. Asphalt shingle and standing-seam metal are the easiest and cheapest. Clay and concrete tile need specialist hooks and cost more in labour. Slate is the most demanding. Flat roofs need ballasted or tilted frames, which changes the whole design.
Shading. Walk your roof plane at 9am, midday and 4pm and note every shadow. Chimneys, vents, dormers, satellite dishes, neighbouring buildings and trees all matter — and trees keep growing.
Electrical panel capacity. Older consumer units frequently need upgrading before a solar system can be connected. This is one of the most common surprise costs, and a good surveyor will flag it before you sign.
If any of this rules out a rooftop install, ground mounting is a legitimate alternative — usually more expensive in racking and trenching, but easier to orient optimally and far easier to clean and maintain.
The installation process, step by step
Step 1 — Site survey and system design
A proper survey involves someone physically on your roof, or at minimum a detailed drone and satellite assessment plus an inspection of your electrical panel. They should measure usable roof area, record the pitch and azimuth of each roof plane, map shading, check rafter spacing and condition, and photograph your existing electrical setup.
What comes out of this is a system design: panel count and layout, string configuration, inverter selection, conduit routing, and a production estimate. Ask for the production estimate in kWh per year and ask what derate factor was used. Anyone unwilling to tell you is guessing.
Before the survey, do your own sizing so you can sanity-check theirs. Our solar panel calculator guide walks through the arithmetic, and the system size calculator gives you a number in under a minute.
Step 2 — Permits, approvals and paperwork
This is usually the slowest stage and it happens entirely without you. Depending on your country and local authority it can involve building permits, electrical permits, utility interconnection applications, net metering registration, homeowners' association approval and structural sign-off.
Timelines vary enormously — a few days in some jurisdictions, several months in others. A competent installer handles all of it and gives you a realistic schedule. Ask specifically who submits the interconnection application and what happens if it's rejected.
If your system will export to the grid, understand your compensation terms before you commit. Our analysis of 2026 net metering changes explains why export rates are shifting and what it means for system design.
Step 3 — Equipment delivery and site preparation
Panels, inverter, racking, cabling and protection devices arrive on site. Inspect the delivery yourself if you can. Check that the panel model and wattage match your contract exactly, and photograph the serial numbers — you will want these for warranty claims years from now.
Substitutions are common and not always disclosed. If the box says a different brand or a lower wattage than your quote, that conversation needs to happen before installation starts, not after.
Step 4 — Mounting and racking
This is where roof leaks are created or prevented. The crew locates and marks your rafters, drills penetrations, installs flashing and mounts, then attaches rails.
The critical details:
Every penetration must be flashed, not just sealed. Sealant alone fails within a few years. Proper flashing integrates with the roof covering so water is directed over it.
Mounts must hit rafters, not just decking. Ask how they locate rafters and whether they verify each one.
Rail spacing must follow the panel manufacturer's specification. Getting this wrong voids the module warranty and creates a wind-uplift risk.
Edge and fire setbacks are required in most jurisdictions and reduce usable roof area — an installer who ignores them is creating a compliance problem for you.
Step 5 — Panel mounting and DC wiring
Panels are clamped to the rails and wired into strings. Good practice looks like this: cables clipped and supported so nothing rests on the roof surface, no cable loops hanging below the array where rodents and UV can reach them, correct polarity throughout, and MC4-type connectors from a single matched manufacturer.
Mixing connector brands is a widespread shortcut that creates high-resistance joints and is a genuine fire risk. It's also invisible from the ground, which is why it happens.
Step 6 — Inverter, AC wiring and protection
The inverter is mounted — ideally in shade, with clearance around it for airflow, and somewhere you can actually reach to read the display. Then come the DC and AC isolators, surge protection devices, earthing conductors and the connection into your consumer unit or main panel.
This stage is what your electrical permit is really about. Earthing and surge protection in particular are the components people never think about until a storm destroys an unprotected inverter — our grounding and surge protection guide explains what should be there and why.
If you're still choosing an inverter, compare specifications in the inverter database and see how two leading brands differ in Huawei vs Sungrow.
Step 7 — Inspection and utility approval
An inspector from the local authority checks the electrical work, and in most jurisdictions the utility separately approves the interconnection and may install or reprogram your meter. Until you have permission to operate, your system legally cannot run — even though it is physically complete. This gap frustrates people, but switching on early can void your interconnection agreement.
Step 8 — Commissioning and handover
The system is energised, the inverter is configured, monitoring is set up, and production is verified against the design estimate.
Do not let the crew leave without giving you:
A single-line electrical diagram of your system
Panel and inverter serial numbers and datasheets
All warranty documents — product, performance and workmanship, which are three separate things
Monitoring login credentials in your own name, not the installer's
A clear shutdown procedure and the location of every isolator
Signed permits and the interconnection approval
Take photographs of the roof before the panels go down and of the wiring before it is covered. Five years from now, when something needs diagnosing, those photos are the only record of what is underneath your array.
What drives installation cost
Hardware is roughly half the price of a residential solar installation. The rest is labour, design, permitting, overheads and margin — which is exactly why quotes for identical equipment can differ by thirty percent or more.
The factors that move the number most:
System size. Cost per kW falls as systems get larger, because fixed costs like design, permits and mobilisation spread across more capacity. A 10 kW system rarely costs twice a 5 kW system.
Roof complexity. A single unobstructed south-facing plane is the cheapest scenario. Multiple planes, steep pitch, three storeys, tile or slate covering, and heavy obstruction all add labour hours.
Electrical work. A panel upgrade, a long conduit run from roof to inverter to meter, or trenching for a ground mount can each add meaningfully.
Equipment tier. Premium modules and inverters cost more upfront and usually carry longer warranties and better degradation curves.
Battery storage. Adding a battery frequently increases the total by a half or more. Decide whether you need one on its own merits, not as an upsell.
Local labour rates and market maturity. The same system genuinely costs very different amounts in different countries — see your country hub for regional pricing.
For current per-kW figures, read Solar Panel Cost 2026. To see what the installed cost means for your bills, run the savings calculator and payback calculator. If you're borrowing, compare structures with the financing comparison tool.
How to compare quotes properly
Get at least three quotes, and insist they are comparable. A cheaper quote is often a smaller or lower-specified system rather than a better deal.
Normalise every quote to price per watt installed — divide the total cost by system size in watts. That single number strips away the marketing and lets you compare like with like. Then check whether the differences are explained by:
Panel brand, wattage, efficiency and degradation warranty
Inverter type — string, hybrid or microinverters — and its warranty length
Estimated annual production and the derate factor behind it
Length of the workmanship warranty, which is the one that covers roof leaks and is entirely down to the installer
Whether monitoring hardware, a panel upgrade, scaffolding, permits and grid application fees are included or excluded
Compare the equipment itself independently before you accept anyone's recommendation. Our comparisons section covers the major panel and battery brands head to head, including LONGi vs Jinko and Tesla Powerwall vs BYD.
Red flags that should end the conversation
Pressure to sign today. Discounts that expire in one visit are a sales technique, not a market condition.
No site survey before quoting. A price given over the phone from a satellite image is a guess.
Refusal to name specific equipment models. "Tier 1 panels" is not a specification.
A production estimate with no derate factor disclosed. Inflated estimates make payback look better than it will be.
No workmanship warranty, or one shorter than about ten years. This is the warranty that covers their errors.
Large upfront deposits. A modest deposit is normal; most of the money should follow delivery and commissioning.
No verifiable licence, insurance or local references. Ask for addresses of recent installations and actually call one.
Vagueness about who owns the monitoring account. It should be you.
How long does it take?
The physical installation of a typical residential system takes one to three days on site. Everything around it takes far longer: survey and design usually a week or two, permits and approvals anywhere from days to several months depending on jurisdiction, and post-installation inspection and utility permission commonly another two to six weeks.
A realistic end-to-end expectation is one to three months from signing to switching on, with permitting as the main variable. An installer who promises two weeks in a slow-permitting region is either inexperienced or not being straight with you.
After installation
Check your monitoring in the first week and compare actual output against the design estimate on a clear day. Small deviations are normal; a persistent shortfall of more than about ten percent deserves a call while everything is still fresh and under warranty.
Beyond that, solar maintenance is genuinely minimal — keep the glass clean, watch for shading as trees grow, and have the electrical work inspected every few years. Our guide on maintenance and troubleshooting covers the routine, and if the inverter ever refuses to start, the inverter troubleshooting video covers the usual causes.
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