A Smaller Array That Saved More

[James: example case study built from the reusable template — replace with a real project, real figures and a customer-approved quote before publishing. Delete the ph class to clear the highlight.]

At a glance

• Location: West Bridgford, Nottinghamshire
• Property type: 1930s semi-detached
• Roof: West-facing main pitch, chimney to the south end
• Annual consumption: 4,100 kWh, with a heavy evening profile
• System installed: 3.8 kWp array, hybrid inverter, 9.5 kWh battery
• Timescale: Surveyed in March, installed over two days in April

The challenge

The owners had a quote from another installer for a 6.4 kWp array with no storage — as many panels as the roof would carry. Both work full time and the house is empty until six, so almost everything that system generated would have been exported at the going rate and bought back a few hours later at four times the price.

What we found on survey

Two things. The chimney shaded the southern end of the main pitch from roughly two o’clock onwards for much of the year, which the earlier quote had not accounted for and which would have dragged down a string wired straight across. And the half-hourly data showed a pronounced evening peak: over sixty per cent of household consumption fell between four and eleven at night.

A west-facing roof is often treated as a disadvantage. Here it was closer to an asset, because it pushes generation later into the afternoon — nearer to when this household actually needed it.

What we designed and installed

A smaller array than the one quoted, laid out to keep the chimney’s shadow off a single string, with optimisers on the three affected modules only. A hybrid inverter so solar and battery run as one system. And a 9.5 kWh battery sized against the measured evening load rather than a round number, on a time-of-use tariff so it also charges cheaply overnight through the winter.

The result

• Self-consumption modelled at around 78%, against roughly 30% for the larger array without storage.
• Lower capital cost than the system originally quoted, and a shorter modelled payback.
• The house rides through the evening peak on stored generation for most of the year.
• Overnight charging carries the winter months when the array contributes little.

In the customer’s words

“[James: replace with a real, customer-approved quote before publishing.]”

The point

More panels is not the same as more saving. Once you are generating more than you can use or store, the extra output is worth the export rate only, and the payback on that last increment is much longer than on the first. Which system is right depends on your evenings — see sizing your system or try the model on the home page.

Send us your annual kWh figure and a photo of the roof and we will tell you what is realistic before anyone visits.

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