Plug-In Solar Payback Calculator

Annual generation starts from your panel's DC wattage multiplied by a regional solar yield figure (kWh per kWp per year, roughly 760–1020 depending on where in the UK you are) and your stated sun exposure. Because up to 2000W of panels can sit behind an inverter fixed at 800W AC, generation above what the inverter can pass through is clipped: the tool applies a simplified clipping-loss estimate that scales with how oversized the panel array is relative to the 800W cap — this is an approximation, not a real inverter simulation.

Self-consumption combines two things, since there's no battery in this pathway to shift generation to when you're not home. First, an optional constant background load (Step 1) — a fridge, freezer, router and other standby devices don't care whether anyone's in, so that draw is treated as covering its own share of the inverter's 800W output range automatically, regardless of occupancy. Second, your occupancy pattern determines how much of whatever's left above that background floor gets used by active appliances and people: around 80% for a household home most of the day, tapering to around 30% for one out most of the day. Leaving the background load blank falls back to occupancy alone. Everything not self-consumed is treated as export. Its value defaults to £0, but you can enter a confirmed export rate in Step 3. SEG/export payments are not automatic: Ofgem requires suitable export metering and suitable installation certification (MCS or equivalent for installations up to 50kW), with eligibility handled by the chosen supplier.

Deliberately not asked: total annual household electricity use. At this scale (well under 2,000 kWh/year even at the legal maximum), annual usage is very rarely the binding constraint on self-consumption — a typical UK home uses several times that much over a year, so the question is almost always whether something is drawing power at the moment the panel is generating, not whether there's enough demand across the year overall. Background load and occupancy answer that timing question directly; annual usage mostly wouldn't. The one edge case where it would matter — a very low-usage home (an occasionally-used holiday let, for example) whose total demand could genuinely fall close to or below what a kit generates — isn't specifically corrected for, so self-consumption may be slightly overstated in that unusual situation.

Savings are simple self-consumed kWh multiplied by your electricity price, held flat except for a 0.5%/year panel degradation assumption in the savings-over-time table — no energy-price inflation is modelled, so if prices rise, real payback will be faster than shown. Simple payback divides kit cost by first-year saving.

Regional yield bands and the six DNO groupings are broad approximations, not certified lookups. Product compliance is deliberately not inferred from the calculator inputs: 800VA AC and 2000W DC are necessary limits for this pathway, but users should verify the exact complete product against its manufacturer evidence and the current ENA Connect Direct record before purchase or connection.