5kW Solar Panel System Cost in the UK

More capacity needs a demand and export explanation

Twelve 450 W modules give 5.40 kWp, while eleven give 4.95 kWp. Those are meaningfully different layouts hidden by a loose 5 kW label. Ask which is actually quoted and whether the extra module positions have good exposure.

A larger array can use a second roof face or a less favourable position. Ask for the marginal generation gained and the added mounting, access or electrical complexity. Bigger annual use does not demonstrate midday use.

Panel area is only the starting measurement

12 example modules have 5.40 kWp capacity when each is 450 W. The Trinasolar example format is 1,762 by 1,134 mm; other models differ. Module-face area excludes edges, gaps, access and obstructions. Check physical panel sizes and rounding.

Ask for the exact data sheet and layout before accepting a quote. Roof condition and fixing details are professional survey questions. Do not use this panel count as an installation plan.

Compare a complete cash scope

Price panels, inverter, mounting, scaffolding, electrical work, commissioning and paperwork. State whether storage, backup, roof repairs and tax are included. A finance payment is not a comparable cash installation total. The cost guide explains the budget boundary.

If quotes differ, ask which difference is design and which is scope. We do not invent an equipment allocation from a bundled total or describe one proposal as market value on the basis of its rounded size.

Test the quoted generation

A synthetic 4,500 kWh generation and 5,000 kWh demand scenario with 40% direct use has 1,800 kWh direct use and 2,700 kWh exports. Example 30p/15p rates give GBP 945 annual benefit before costs. This does not specify a suitable battery size.

Run the shared payback calculator with your own generation and cost, direct-use assumption and tariffs. A household statement measures annual demand; direct use is an estimate of the overlap with generation. Keep standing charges outside the saving calculation.

A battery is a separate decision

Request the same array without storage and itemise the additional battery work. Capacity alone does not predict annual savings. Check usable capacity, losses and forgone exports, especially if you already receive FIT payments. Check the proposal before comparing payback claims.