How to Price Solar PV Panel Installation: System Size, Labour and DNO Applications

Quick Answer: A typical UK domestic solar PV system in 2026 costs £4,500–£9,500 supply-and-fit for a 3.5 kWp to 6 kWp system on a standard pitched roof. Panels £130–£280 each (typically 8–16 panels for 3.5–6 kWp), inverter £600–£1,500, mounting kit £400–£900, electrical install £1,200–£2,500. Battery storage adds £3,500–£8,500 for 5–13.5 kWh capacity. Microgeneration Certification Scheme (MCS) accreditation is required for grant eligibility, Smart Export Guarantee (SEG) participation, and most insurance recognition. Building Regulations Part P applies; DNO G98/G99 application is mandatory for grid connection.

Summary

Solar PV in the UK has reached grid parity many times over for domestic generation. A 4 kWp south-facing system in the south of England typically generates 3,800–4,200 kWh per year, paying back £1,200–£1,800 annually in displaced grid electricity at 2026 prices, with payback under 5 years and a 25-year+ system life. Customer demand is high, particularly with battery storage that allows time-shifted self-consumption.

For an installer pricing the work, the variables are roof orientation and pitch (south-facing 30–35° is optimal), shading, roof construction (tile, slate, metal), system size, inverter and battery selection, and DNO connection capacity. A standard 4 kWp install on a south-facing tile roof is a 1–2 day job for a 3-person crew. Larger systems with battery storage and EV charger integration take 2–3 days.

The compliance landscape is settled. Microgeneration Certification Scheme (MCS) accreditation is the gold standard for installers — required for the customer to participate in the Smart Export Guarantee (selling exported electricity to suppliers) and for most insurance/lender recognition. Building Regulations Part P applies (notifiable electrical work). DNO (Distribution Network Operator) application — G98 for sub-3.68 kW, G99 for above — must be approved before commissioning. Skip the DNO step and the system is illegal to connect to the grid.

Key Facts

Quick Reference Table

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System size Panels (typical) Total fitted cost Annual generation (S-facing) Annual savings
2 kWp 5 £3,500–£5,000 1,900–2,100 kWh £600–£900
3 kWp 7 £4,200–£6,000 2,800–3,200 kWh £900–£1,400
4 kWp 10 £5,000–£7,500 3,800–4,200 kWh £1,200–£1,800
5 kWp 12 £6,000–£8,500 4,700–5,300 kWh £1,500–£2,200
6 kWp 14 £7,000–£9,500 5,700–6,300 kWh £1,800–£2,600
8 kWp 18 £9,500–£13,500 7,500–8,300 kWh £2,400–£3,500
10 kWp+ 24+ £12,000–£18,000 9,500+ kWh £3,000–£4,500

Detailed Guidance

System Sizing

The system is sized based on:

  1. Annual electricity consumption — typical 3-bed semi uses 2,700–3,800 kWh/year
  2. Roof area available — 1.7 m² per typical 410 W panel
  3. Roof orientation and pitch — south-facing 30–40° is optimal
  4. Shading — trees, neighbouring buildings, chimneys reduce output
  5. Customer's intention — self-consumption-focused or maximum export

Common targets:

A common mistake is oversizing without battery — without a battery, exported electricity earns only 5–15p/kWh while imported costs 25–30p/kWh. The benefit comes from self-consumed generation, and self-consumption rates are limited by the household's daytime usage profile.

Panel Selection

UK domestic panels in 2026 typical specs:

Major brands: JA Solar, LONGi, Trina, JinkoSolar, REC, SunPower (premium). All Tier 1 manufacturers; performance differences <5% in real-world operation.

Inverter Choice

String inverter:

Hybrid inverter:

Microinverter or DC optimiser:

Mounting

Standard on-roof (pitched tile):

In-roof (integrated):

Flat roof:

Ground mount:

DNO Application (Grid Connection)

G98: For systems up to 16 A per phase (3.68 kW single-phase, 11 kW three-phase). Notification only — no permission required. Submitted within 28 days of commissioning.

G99: For systems above 16 A per phase. Application BEFORE installation. DNO has 11 weeks to respond. May require:

The DNO is the local distribution network — UK Power Networks, Western Power, Northern Powergrid, etc. Identify the right DNO from the customer's electricity bill.

Battery Storage

Battery types and brands (2026):

Sizing rule of thumb: 1 kWh battery per kWp PV is a good baseline. Larger batteries don't fully charge from solar alone in winter; smaller batteries don't time-shift enough peak generation.

Building Regulations and Notifications

Part P (electrical safety): Mandatory. Self-certified by competent persons scheme contractor.

Part L (energy): Solar PV typically improves SAP rating; not directly notifiable but can support Part L compliance for new dwellings.

Part B (fire): Affects installation if panels are within 6 m of boundary or 2.3 m of a window. Refer to Approved Document B.

Planning: Permitted development for most installations on existing dwellings. Conservation areas and listed buildings are exceptions — Article 4 directions also strip rights. Confirm before quoting.

MCS Certification

Microgeneration Certification Scheme (MCS):

Smart Export Guarantee

The current export tariff scheme (replaced FiT in 2020):

Compare tariffs for the customer; not always best to stay with their current supplier.

Frequently Asked Questions

What's the payback period?

A 4 kWp system at £5,500 saving £1,200/year displays 4.6 year payback. With battery storage at £8,500 saving £1,500/year, payback is 5.7 years. Both well within 25-year warranties on panels and 10-year warranties on inverters.

Should I add a battery now or later?

Adding a battery later requires either replacing the inverter with a hybrid model (expensive — £1,000+ in labour and downtime) or adding an AC-coupled battery system (compatible with most existing inverters but costs slightly more in equipment). Best practice: install a hybrid inverter at the start, even without a battery, so battery upgrade is straightforward later.

What about the MCS certification cost?

MCS certification is included in the installer's price; customers don't pay separately. The accreditation requirement falls on the contractor, not the customer.

What about a roof I want to renew?

If the roof is over 20 years old, replace it BEFORE installing solar. PV systems have a 25-year+ life and removing/refitting them for re-roofing later costs £800–£1,500. Ideally the roof and PV are installed/replaced together.

Will solar invalidate my home insurance?

Most insurers accept MCS-certified solar installations without issue. Some discount premiums; some increase. Always notify the customer's insurer in writing once the system is installed.

What about the battery during a power cut?

By default, grid-tied solar systems shut down during a power cut (anti-islanding) — even with battery, the household has no power. Battery + EPS (Emergency Power Supply) functionality maintains essential circuits during outages. Check inverter spec; not all support EPS.

Regulations & Standards