The Ultimate Guide to Installing Solar PV

Technical

How solar works & what you’ll need

How do solar panels work, and do they generate power on cloudy days?

Solar panels convert sunlight into electricity using photovoltaic (PV) cells. When light hits the cells it excites electrons, generating direct current (DC) electricity. An inverter then converts that DC into the alternating current (AC) your home or business actually uses.

Panels produce the most in direct sunlight, but they still generate on cloudy days — they capture diffuse daylight, just at a lower output. How much depends on cloud density and the time of year. UK winters produce less than summers, which is why we size systems against your real annual consumption rather than a single sunny day.

What are the three main types of system?

What size system do I need?

The right size comes down to a handful of factors:

• Energy consumption — check your bills for your annual usage in kWh; this is the biggest driver.
• Roof space — how many panels physically fit, and on which pitches.
• Panel efficiency — higher-output panels generate more in less space when the roof is tight.
• Location & orientation — how much sun the roof sees, and which way it faces.
• System losses — inverter losses, shading and soiling, typically allowed for at around 10–25%.

As a rough rule, 1 kWp of panels generates around 3–4 kWh a day in the UK averaged over the year. A home using roughly 30 kWh a day might therefore look at a 7–10 kWp system. We confirm the right figure with a proper design based on your actual usage — never a guess.

Will the system work during a power cut?

A standard grid-tied system shuts down automatically during an outage — this is a safety requirement to protect engineers working on the network. A hybrid or off-grid system, however, can keep going:

• Hybrid — isolates from the grid and runs chosen circuits from the battery.
• Off-grid — runs entirely from stored energy, independent of the network.

If keeping the lights on through an outage matters to you, tell us at quote stage and we’ll design in battery backup and, where wanted, a whole-house changeover.

What are the essential parts of a solar system?

• Solar panels — capture sunlight and produce DC electricity.
• Inverter — converts DC to the AC your appliances use. We fit Solis hybrid inverters as standard.
• Mounting system — holds the panels securely at the right angle, on roof or ground.
• Battery (optional) — stores surplus for evenings or outages. We use Fogstar on domestic systems.
• Wiring & protection — cabling, isolation and connections for safe operation.
• Monitoring — tracks generation and performance so issues are spotted early.

How long do panels last, and what maintenance do they need?

Solar panels typically last 25–30 years and keep generating beyond that at a gradually reduced output — most lose only around 0.5–1% of their efficiency a year. They are low-maintenance:

• Cleaning — usually once or twice a year to clear dirt and debris; more often in dusty spots.
• Inspection — a professional check every 2–3 years on mounts, wiring and the inverter.
• Inverter — tends to be the first component to need replacing, often after 10–15 years.

Do I need a battery?

A battery isn’t essential, but it’s worth it for many people. Consider one if you want resilience during outages, more independence from the grid, the ability to charge cheaply overnight and use that energy at peak times, or you’re aiming for off-grid living. If you rarely lose power and your main goal is straightforward bill savings with SEG export, you may not need one. We’ll talk you through the trade-off honestly for your situation.

Installation & property

Getting solar onto your roof

Is my roof suitable (size, orientation, shading)?

• Size — each panel is roughly 2 m², so we check there’s room for the array your usage needs.
• Orientation — south-facing is ideal in the UK, but east and west work well too, often as an east/west split.
• Shading — trees, chimneys and neighbouring buildings reduce output; optimisers can help where shading is unavoidable.
• Roof condition — the roof should be sound with plenty of life left, since the panels will be up there for decades.

Do I need planning permission?

Most domestic roof-mounted installations fall under permitted development and don’t need a formal application. There are exceptions — listed buildings, conservation areas, and some larger or commercial systems may require permission. We check this for you and handle the process where it’s needed, so it’s one less thing to worry about.

What happens if I sell the property?

Solar typically makes a home more attractive to buyers thanks to the lower bills and export income. The system stays with the property, and any remaining manufacturer warranties and your SEG arrangement can usually transfer to the new owner — a genuine selling point. Your estate agent can advise on how it’s best presented for your local market.

Will solar panels damage my roof?

No — when installed correctly, panels don’t damage your roof, and they can even shelter the covering beneath them. Problems only arise from poor workmanship. We use quality mounting systems and proper weatherproofing, and our installation work is backed by a 5-year workmanship guarantee. If your roof needs attention, it’s best sorted before the panels go on.

What’s the installation process and timeline?

• Site survey — we confirm the design, roof and electrics. The survey is free and follows quote acceptance.
• Design & DNO application — we finalise the design and apply to your network operator (G98/G99) where required.
• Installation — mounting, panels, inverter and any battery, typically 1–3 days depending on system size.
• Commissioning & handover — testing, certification and the paperwork you need for SEG.

Allowing for DNO timescales, the whole process usually runs over a few weeks. Every quote we give is subject to that site survey.

How many panels will I need?

It comes down to your consumption and the panels used. Modern panels are typically 450–550 W — we specify 500 W or higher all-black Tier-1 panels (JA Solar or Aiko) as standard. As a rough guide, an average home might need somewhere in the region of 10–16 panels, but the exact number falls out of a proper design based on your usage and roof.

Ownership

Warranties & maintenance

Every Spectrum installation is protected on three fronts: manufacturer warranties on the equipment, our 5-year workmanship guarantee on the install, and £1M professional-indemnity cover on the system design — all underpinned by a QANW insurance-backed guarantee. Maintenance is light: an occasional clean, a professional inspection every 2–3 years, and keeping an eye on inverter performance via monitoring.

FAQs

Quick answers