Solar Panel Size Guide: Dimensions & Roof Space

2026 residential panel sizes:

| Wattage | Dimensions (mm) | Area (m²) | Weight (kg) | Cells | |---------|-----------------|-----------|-------------|-------| | 370W | 1,755 × 1,038 | 1.82 | 19 | 60 | | 385W | 1,722 × 1,134 | 1.95 | 20 | 66 | | 400W | 1,722 × 1,134 | 1.95 | 21 | 66 | | 410W | 1,722 × 1,134 | 1.95 | 21 | 66 | | 425W | 1,762 × 1,134 | 2.00 | 22 | 66 | | 440W | 2,094 × 1,038 | 2.17 | 25 | 72 | | 500W+ | 2,278 × 1,134 | 2.58 | 28 | 72+ |

Key points: - Most UK residential installations use 60-cell or 66-cell panels (1.7m × 1.0–1.1m) - 72-cell panels (2.1m+ long) are primarily for commercial installations - The trend is toward higher wattage in the same physical size (more efficient cells) - Frame depth is consistently 30–35mm across all manufacturers

Source: Panel manufacturer specification sheets (JA Solar, Trina, Longi, Canadian Solar).

Quick calculation: 1. Estimate your usable roof area (one slope, in m²) 2. Divide by 2.0 (m² per panel including spacing) 3. Result = approximate number of panels

Example: - 3-bed semi, south-facing slope: ~18m² - 18 ÷ 2.0 = 9 panels (~3.6kW)

Typical roof capacities:

| House Type | Usable Roof (one slope) | Panels | System Size | |-----------|------------------------|--------|------------| | 2-bed terrace | 10–15m² | 5–7 | 2–2.8kW | | 3-bed semi | 15–22m² | 7–11 | 2.8–4.4kW | | 3-bed detached | 18–28m² | 9–14 | 3.6–5.6kW | | 4-bed detached | 25–40m² | 12–20 | 4.8–8kW | | 5-bed detached | 30–50m² | 15–25 | 6–10kW |

Factors that reduce usable area: - Dormer windows - Chimneys (and their shadows) - Skylights/roof windows - Vent pipes - Hip roof edges (panels cannot extend to the angled edge) - Building regulations setback from roof edge (150mm minimum)

Your installer measures exact dimensions during the site survey — these are rough guides.

Source: Standard UK roof dimensions; MCS panel spacing guidelines.

Panels can be mounted in two orientations:

Portrait (vertical — most common): - Panel stands tall: 1.7m high × 1.1m wide - Fits better on narrower roofs - Standard mounting rail layout - Works well with most string inverter configurations

Landscape (horizontal): - Panel lies flat: 1.1m high × 1.7m wide - Fits better on wider, shallower roofs - Can fit more panels on low-pitch roofs - May require different mounting rail spacing

Which is better? In terms of output: identical — orientation does not affect generation. Choose based on which fits more panels on your specific roof shape. Your installer will optimise the layout.

Mixing orientations: Possible but not recommended with a string inverter (voltage mismatch). With micro-inverters, mixing portrait and landscape is fine — each panel is independent.

Source: MCS installation design guidance.

Between panels: 20–30mm gap between adjacent panels for clamp clearance and thermal expansion.

From roof edges: 150mm minimum setback from all edges (ridge, eaves, verge, hips) for wind loading compliance and safe access.

Between rows (flat roof): Rows must be spaced to prevent one row shading the next. Rule of thumb: 1.5× panel height in spacing. For a 1.7m panel at 25° tilt: ~1.1m between rows. This means flat roof systems use more area per panel than pitched roof systems.

From chimneys: Leave adequate clearance (300mm+) to avoid shading and allow rain runoff.

From skylights/roof windows: Panels cannot cover skylights. Leave 300mm+ clearance for access and fire regulations.

Source: MCS panel spacing and edge setback requirements.