Having solar panels installed is one of the best home improvements you can make, but the process can feel daunting if you don’t know what to expect. From initial survey to generating your first kilowatt, a typical residential installation takes 6–10 weeks from enquiry to completion, with the actual roof work taking just 1–2 days.
This guide walks through every stage of the process so you know exactly what happens, when, and what questions to ask your installer along the way.
Before Installation Day
1. Initial Site Survey
An MCS-certified installer will visit your property to assess suitability. During the survey they will check your roof’s orientation and pitch (south-facing at 30–40° is ideal), measure available roof space, inspect your roof condition and structural integrity, assess any shading from trees, buildings or chimneys, check your consumer unit (fuse board) and existing wiring, and discuss your electricity usage patterns.
The survey typically takes 45–90 minutes. A reputable installer will never pressure you into signing on the day. If they do, consider it a red flag.
2. System Design & Quotation
Based on the survey, your installer will design a system and provide a detailed quotation. This should include the number and type of panels, inverter specification (string or micro-inverters), estimated annual generation in kWh, projected savings and payback period, total cost including VAT (0% VAT on residential solar since 2022), warranty terms for panels, inverter and workmanship, and an installation timeline.
| System Size | Number of Panels | Roof Space Required | Typical Cost | Annual Generation |
|---|---|---|---|---|
| 3 kW | 7–8 | 12–15 m² | £5,000–£6,000 | 2,500–3,000 kWh |
| 4 kW | 10–11 | 16–20 m² | £6,000–£8,000 | 3,400–4,000 kWh |
| 5 kW | 12–14 | 20–25 m² | £7,000–£9,000 | 4,200–5,000 kWh |
| 6 kW | 15–17 | 25–30 m² | £8,000–£11,000 | 5,000–6,000 kWh |
3. Paperwork & Approvals
Your installer handles most of the paperwork, but be aware of what’s involved. Most residential installations fall under permitted development and don’t need planning permission (see our planning permission guide). Your installer will apply to your Distribution Network Operator (DNO) for permission to connect the system to the grid. This is called a G99 application for systems over 3.68 kW, or G98 for smaller systems. DNO approval typically takes 10–25 working days.
4. Scaffolding
Scaffolding is erected the day before or morning of installation. It typically costs £300–£600 and should be included in your quote. The scaffolding remains in place for 1–3 days depending on the installation complexity. Make sure there’s clear access around your property for the scaffolding team. You may need to move cars, bins, or garden furniture temporarily.
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Installation Day: What Happens
The actual installation typically takes 1–2 days for a standard residential system (3–6 kW). Here’s what happens hour by hour:
Morning (8:00–12:00): Roof Work
The installation team (usually 2–3 people) arrives and begins mounting the rail system on your roof. This involves lifting roof tiles, attaching mounting brackets to the rafters, replacing the tiles with weatherproof flashing, and securing aluminium rails to the brackets. This is the noisiest part of the process. You’ll hear drilling from inside the house, but there should be no damage to your interior.
Late Morning (10:00–13:00): Panel Mounting
Once the rails are secure, the panels are lifted onto the roof and clipped into position. Each panel weighs approximately 18–22 kg. The panels are connected in series (strings) using MC4 connectors, and DC cabling is routed down through the roof space to where the inverter will be mounted.
Afternoon (13:00–16:00): Electrical Work
An electrician (often part of the installation team) installs the inverter, usually in your garage, loft, or utility room. They connect the DC cabling from the roof to the inverter, wire the inverter’s AC output to your consumer unit, install an isolator switch (required by regulations), fit a generation meter to track how much electricity you produce, and configure the system monitoring (most modern inverters have Wi-Fi and an app).
Late Afternoon (15:00–17:00): Testing & Commissioning
The installer runs a series of tests including earth continuity, insulation resistance, polarity checks, and open circuit voltage measurements. They’ll switch on the system and verify it’s generating correctly. You should see live data on the inverter display or monitoring app immediately.
After Installation
DNO Notification
Your installer must notify your DNO within 28 days of commissioning. This is a legal requirement and your installer handles it. The DNO may install or upgrade your electricity meter to a smart meter that can measure both import and export.
MCS Certificate
Your installer issues an MCS certificate within 10 working days. This is essential documentation — you need it to register for the Smart Export Guarantee (SEG), which pays you for electricity you export to the grid at 4–6p per kWh. Keep your MCS certificate safe alongside your warranties and electrical certificates.
Smart Export Guarantee (SEG)
Once you have your MCS certificate, register with an energy supplier offering SEG payments. You don’t have to use your existing supplier. Current SEG rates range from 4p to 15p per kWh depending on the supplier and tariff type (fixed vs variable). Octopus Energy, EDF, and British Gas are popular choices with competitive rates.
Installation Timeline Summary
| Stage | Duration | What Happens |
|---|---|---|
| Site survey | Week 1–2 | Installer visits, assesses roof, provides quote |
| Design & DNO application | Week 2–4 | System designed, paperwork submitted |
| DNO approval | Week 3–6 | Wait for grid connection permission (10–25 days) |
| Scaffolding | Day before install | Scaffold erected around roof area |
| Installation | 1–2 days | Panels mounted, wired, inverter installed |
| Commissioning | Same day | System tested and switched on |
| MCS certificate | Within 10 days | Official certificate issued |
| SEG registration | Within 1 month | Register for export payments |
Questions to Ask Your Installer
- Are you MCS certified? — This is non-negotiable. Without MCS certification you cannot claim SEG payments.
- What panels and inverter will you use? — Get exact model numbers. Research them independently before signing.
- What warranties are included? — Expect 25 years on panels, 5–12 years on inverters, and 5–10 years on workmanship.
- Is scaffolding included in the price? — It should be. If it’s listed as an extra, negotiate.
- Will you handle the DNO application? — Yes, they should. This is standard practice.
- Can I see examples of previous installations? — Reputable installers will happily share photos or references.
- What happens if there’s a problem after installation? — Understand their aftercare process and response times.
Common Installation Problems to Watch For
Most installations go smoothly, but be aware of these potential issues. Roof condition surprises can add cost if tiles are cracked or battens need replacing. Shading that wasn’t identified during the survey can reduce performance. Incorrect inverter sizing (too small for the panel array) limits generation. Poor cable routing through the loft that isn’t tidy or properly clipped. And missing or delayed MCS certification, which prevents you registering for SEG payments.
If anything doesn’t look right during or after installation, raise it with your installer immediately. Document everything with photos.
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