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Plug-In Solar Real-World Results: What We Found

Updated 24 March 20268 min read

Marketing claims are one thing. Real-world performance is another. We've gathered data from UK plug-in solar setups to show what you can actually expect — the good, the underwhelming, and the surprising.

The Test Setups

We've compiled data from five real UK plug-in solar installations, each running for at least 12 months:

Setup	Location	Panels	Orientation	Mounting
A	Bristol	2 × 405W Trina	South, 30° tilt	Garden ground frame
B	Manchester	1 × 400W JA Solar	West, vertical (wall)	Balcony wall mount
C	Cambridge	2 × 410W Canadian Solar	South-east, 25° tilt	Shed roof
D	Edinburgh	1 × 420W LONGi	South, 35° tilt	Garden ground frame
E	London	2 × 400W	South-west, railing	Balcony railing mount

All use Hoymiles microinverters and feed into a standard 13A socket.

12-Month Generation Results

Setup	Rated Capacity	Annual Generation	Yield (kWh/kWp)	% of Theoretical Max
A (Bristol, south)	810W	738 kWh	911	85%
B (Manchester, west wall)	400W	218 kWh	545	55%
C (Cambridge, SE shed)	820W	642 kWh	783	78%
D (Edinburgh, south)	420W	316 kWh	752	80%
E (London, SW balcony)	800W	584 kWh	730	75%

Key observations:

Setup A (Bristol, south-facing, ground frame at optimal tilt) performed best — 85% of theoretical maximum. This matches what you'd expect from a well-positioned installation, even compared to professional roof systems.

Setup B (Manchester, vertical west-facing wall) performed worst — 55% of theoretical. The combination of west orientation (losing morning sun) and vertical mounting (suboptimal angle) significantly reduced output. This is still 218 kWh — worth about £57/year — but the payback stretches to 6–7 years on a single-panel setup.

Monthly Generation Breakdown

Setup A (Bristol, 810W, south-facing) — monthly kWh:

Month	Generation	Daily Average
January	18 kWh	0.6 kWh
February	28 kWh	1.0 kWh
March	55 kWh	1.8 kWh
April	82 kWh	2.7 kWh
May	102 kWh	3.3 kWh
June	108 kWh	3.6 kWh
July	105 kWh	3.4 kWh
August	91 kWh	2.9 kWh
September	68 kWh	2.3 kWh
October	42 kWh	1.4 kWh
November	22 kWh	0.7 kWh
December	17 kWh	0.5 kWh

The seasonal swing is dramatic: June generates 6 times more than December. This is typical for all UK solar, not specific to plug-in systems.

Self-Consumption Analysis

Since plug-in systems can't claim SEG payments (no MCS certification), self-consumption is everything. Any exported electricity is free to the grid.

Setup	Self-Consumption Rate	Electricity Saved	Value (at ~24p/kWh — verify current rate)
A (WFH household)	82%	605 kWh	£145
B (Flat, one person)	91%	198 kWh	£48
C (Family, partial WFH)	74%	475 kWh	£114
D (Retired couple)	88%	278 kWh	£67
E (Couple, WFH)	78%	456 kWh	£109

Self-consumption rates are high — 74–91%. This is because plug-in systems are small enough that most generation is absorbed by the household's base load (fridge, router, standby devices, working-from-home equipment).

Small Systems Have High Self-Consumption

Paradoxically, smaller solar systems often have better financial efficiency per kWh than larger ones. A 800W plug-in system with 80% self-consumption saves at the full import rate for most of its output. A 4kW roof system with 40% self-consumption saves at the import rate for less than half its output and earns only the lower SEG export rate (typically 3–15p/kWh) for the rest. Size isn't everything.

Financial Returns

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Setup	Total Cost	Annual Saving	Payback Period
A	£650	£145	4.5 years
B	£380	£48	7.9 years
C	£700	£114	6.1 years
D	£420	£67	6.3 years
E	£680	£109	6.2 years

Setups A, C, D, and E all achieve payback under 6 years — competitive with professional roof installations. Setup B's payback is longer due to the suboptimal west-facing vertical position.

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What We Learned

1. Orientation Matters More Than You'd Think

The difference between south-facing at 30° (Setup A: 911 kWh/kWp) and west-facing vertical (Setup B: 545 kWh/kWp) is 40%. If you have a choice of where to put your panels, south-facing wins convincingly.

2. Tilt Angle Matters

Vertical panels (wall-mounted) generate roughly 25–35% less than optimally tilted panels (30–35°). If you can angle your panels even slightly, do it.

3. Microinverter Efficiency Is Good

The Hoymiles microinverters across all setups showed 95–97% conversion efficiency. No significant losses from the inverter.

4. Shading Is the Enemy

Setup C initially had 15% higher output before a neighbour's tree grew and introduced afternoon shading from May onwards. The June-August output dropped noticeably in year 2. Even partial shading on a single panel significantly reduces output.

5. Cleaning Made Minimal Difference

Panel cleaning was tested on Setup A — cleaning in August after 6 months of no cleaning improved output by approximately 2%. Not worth the effort for these small setups unless panels are under trees or near a busy road.

6. Winter Output Is Minimal But Real

Even in December, every setup generated something. Setup A produced 17 kWh in December — enough to offset the fridge's monthly consumption. It's not much, but it's not zero.

Don't Believe Inflated Claims

Some plug-in solar vendors quote generation figures based on southern European conditions or optimal lab measurements. Real UK generation is 20–45% lower than these claims, depending on your location and setup. Use the figures in this article — based on real UK data — for your planning.

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Recommendations Based on Our Results

Best Setup for Most People

Two panels (800W total), south-facing, ground-mounted at 30° tilt, with a Hoymiles HMS-800 microinverter. Expected generation: 600–750 kWh/year. Cost: £550–£700. Payback: 4–5 years.

Best Setup for Balconies

Two panels on a south-facing balcony railing. Expected: 450–600 kWh/year. Less optimal angle but still worthwhile.

Skip Unless You Have No Alternative

Single panel on a north-facing or heavily shaded wall. Generation drops below 200 kWh/year, extending payback beyond 8 years.

How These Compare to Full Roof Systems

Metric	Plug-In (800W)	Roof System (4kW)
Annual generation	600–750 kWh	3,400–3,800 kWh
Annual saving	£120–£160	£600–£900
Cost	£550–£700	£6,000–£8,000
Payback	4–5 years	7–11 years
kWh per £ invested	~1.0 kWh/£/year	~0.5 kWh/£/year

Plug-in solar delivers more generation per pound invested because of higher self-consumption rates and lower installation costs. But in absolute terms, a roof system generates far more and saves far more. They serve different needs and budgets.

For full details on setting up a plug-in system, see our plug-in solar guide.

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