Solar vs ISAs vs Stocks: Best Investment?

Is solar a better investment than an ISA?

We modelled £8,000 invested in four options over 25 years: SOLAR PANELS (4kW system): Annual return: £780/yr (9.75% on £8,000). Tax status: 100% tax-free. 25-year total: £19,500. Inflation protection: YES (savings grow with electricity prices). Risk: very low (proven technology, 25yr warranty). CASH ISA (4.5% rate): Annual return: £360/yr. Tax status: tax-free. 25-year total: £24,000 (compound interest). Inflation protection: NO (real returns ~1-2%). Risk: zero. STOCKS & SHARES ISA (8% average): Annual return: £640/yr (average). Tax status: tax-free. 25-year total: £54,800 (compound interest). Inflation protection: partial. Risk: HIGH (volatile, could lose 40%+ in a crash). PREMIUM BONDS (1.4% prize rate): Annual return: £112/yr (expected). 25-year total: £2,800. Risk: zero but very low return. VERDICT FOR HOMEOWNERS: Solar delivers the best RISK-ADJUSTED return. It beats Cash ISAs on return, matches S&S ISAs on return but with far less risk, and provides inflation-linked income from day one. Sources: Bank of England base rate (bankofengland.co.uk), FTSE All-Share 25yr average return, NS&I Premium Bond odds, Ofgem (ofgem.gov.uk).