Plug-in solar and rooftop solar are both solar. That's where the similarity largely ends. They serve different buyers, require different budgets, and the decision between them is more nuanced than most guides suggest. This is the honest comparison without a predetermined conclusion.
Cost
Plug-in solar: £419–£499 for an 800W kit — see our best kits guide for current options. No installation cost if you self-install. Total outlay: £419–£499.
Rooftop solar: £8,000–£15,000 for a typical 3.5–5kWp system including MCS installation. Battery storage adds £3,000–£5,000. The cost difference is roughly 20–40x. That's the central fact of this comparison, and most of the analysis flows from it.
Generation
Plug-in solar (800W): 580–780kWh annually. Rooftop solar (4kWp): 3,200–3,800kWh annually — approximately five times as much. But savings are closer to 3–4x, because rooftop solar exports significant generation to the grid at around 15p/kWh on SEG, whereas plug-in solar owners currently export for free. The maths isn't as simple as the panel count suggests.
Who rooftop solar is right for
Homeowners who own their property, have a south-facing roof, plan to stay 10+ years, and have the capital for a large upfront investment. Annual savings of £800–£1,400 with battery give a payback of 8–15 years — long, but positive over the 25-year panel lifespan. If you tick all those boxes and have £10,000 to invest, rooftop solar is the more powerful option.
Who plug-in solar is right for
Renters — see our renters guide and legal rights article — homeowners who want to start without a large outlay, and people in flats or houses without suitable roofs. Also homeowners who already have rooftop solar and want to capture additional generation from surfaces their MCS installer couldn't use. Use our payback calculator to understand the return for your specific household.
Can you have both?
Yes. Plug-in solar on a south-facing fence or garden structure generates independently of rooftop panels and can use surfaces MCS installers wouldn't normally access. For a home that already has 4kWp on the roof, adding plug-in panels can increase total generation by 15–25% for under £500 additional outlay. With July bills rising sharply, maximising self-generation from every available surface is increasingly worth the calculation.
