Solar Panel Cost Per kWh: How Cheap Is Solar?

The formula:

LCOE (Levelised Cost of Energy) = Total Lifetime Cost ÷ Total Lifetime Generation

Example: 4kW system

| Cost Component | Amount | |---------------|--------| | Installation (0% VAT) | £6,750 | | Inverter replacement (year 12) | £1,000 | | Cleaning (8 × £100) | £800 | | Total lifetime cost | £8,550 |

| Generation Component | Amount | |--------------------|--------| | Year 1 output | 4,000 kWh | | 25-year output (with 0.4%/yr degradation) | ~95,000 kWh | | Total lifetime generation | ~95,000 kWh |

LCOE = £8,550 ÷ 95,000 kWh = 9.0p per kWh

With minimal maintenance (no cleaning): LCOE = £7,750 ÷ 95,000 kWh = 8.2p per kWh

With a larger 6kW system (economies of scale): LCOE = £10,500 ÷ 142,000 kWh = 7.4p per kWh

Key comparison: - Solar LCOE: 7–9p per kWh (FIXED for 25 years) - Grid rate 2026: 24.5p per kWh (and historically rising 5–7%/year)

Solar electricity is 3x cheaper than grid electricity — and the gap widens every year.

Source: LCOE calculation methodology; Ofgem Q1 2026 price cap.

Solar has a unique financial characteristic: your cost per kWh DECREASES over time.

Why: 1. You pay the full installation cost upfront (or on finance) 2. After payback (year 8–12), your ongoing cost drops to near zero 3. From year 12 onwards, your only cost is the occasional clean and eventual inverter replacement 4. Meanwhile, the panels keep generating 85–95% of original output for free

Your effective cost per kWh over time:

| Period | Cost per kWh | |--------|-------------| | Years 1–8 (during payback) | ~17p (but you are building equity in the system) | | Years 9–12 (post-payback, pre-inverter) | ~0p (system paid off, inverter still working) | | Year 12 (inverter replacement) | ~1.3p (£1,000 ÷ remaining 75,000 kWh) | | Years 13–25 | ~0p (all costs paid, panels keep generating) |

Effective cost over full 25 years: 7–9p/kWh Effective cost in years 13–25: essentially 0p/kWh

No other energy source gets cheaper the longer you use it.

Source: LCOE methodology; solar financial modelling.

Assuming 3% annual grid price increase:

| Year | Grid Price (p/kWh) | Solar Cost (p/kWh) | Saving per kWh | |------|-------------------|-------------------|----------------| | 2026 | 24.5p | 7p | 17.5p | | 2030 | 27.6p | 7p | 20.6p | | 2035 | 32.0p | 7p | 25.0p | | 2040 | 37.1p | 7p | 30.1p | | 2045 | 43.0p | 7p | 36.0p | | 2050 | 49.8p | 7p | 42.8p |

By 2050: Grid electricity could cost 50p/kWh — 7x your solar cost. Every kWh of solar saves you 43p. The financial advantage of solar compounds over time.

This is why waiting to install costs you money. The sooner you lock in your solar cost per kWh, the more years you benefit from the widening gap.

Source: Historical UK electricity price trends; conservative 3% annual projection.