Is solar PV worth it? Payback and disadvantages
Sources checked
PV pays back through electricity purchases it actually avoids and the net value of surplus electricity. Multiplying all annual generation by the full electricity price on your bill overstates the benefit when exports, fees and fixed charges are treated incorrectly.
Match generation with use
Two homes using 6,000 kWh annually may consume very different amounts during solar hours. Use interval data where available and distinguish direct solar use, battery delivery, imports, exports and losses. A higher self-sufficiency percentage does not necessarily mean a better financial return.
For stored energy, account for losses and the export income you give up. Assess the extra battery investment against its extra benefit rather than assigning the whole system's savings to the battery.
Calculate a transparent scenario
Annual benefit equals avoided import value plus export value, less additional annual fees and operating costs. Net investment equals total investment less the support entered in the scenario. Simple payback divides investment by a positive annual benefit; a non-positive benefit produces no positive simple payback.
Include the full installed scope. Model financing, degradation, replacements and changing prices separately when they matter. Simple payback alone does not include those effects or the time value of money.
Check when it may not make sense
A shaded or soon-to-be-replaced roof, low daytime use, costly connection work or weak export terms can undermine the case. Ask the supplier to show a less favourable scenario with lower useful production and higher costs. Backup resilience may have value to you, but identify that value separately from financial savings.