30 years of irradiance data, Tier 1 hardware and a fully accredited installation team
The most common concern we encounter from commercial clients considering solar for the first time is straightforward: does it actually work given the UK's weather?
The answer, particularly in the South East of England, is clearly yes — and it is supported by over 30 years of measured irradiance data, not projections or marketing claims. Solar panels generate electricity from daylight, not direct sunshine. Cloud cover reduces output, but it does not eliminate it. A well-designed system in the South East generates reliably across all twelve months of the year.
Generation estimates for commercial solar are calculated using the EU Commission's PVGIS (Photovoltaic Geographical Information System) dataset, which incorporates over three decades of satellite-measured solar irradiance data for every location in Europe. This data is used by every accredited installer operating under the MCS MIS 3002 methodology — the UK's mandatory standard for certified solar calculations.
The South East of England sits within MCS Irradiance Zone 2, one of the highest-yield bands in England. The relevant yield factor for a south-facing, low-pitch commercial roof in this zone is approximately 955 kWh of generation per kWp of installed capacity per year.
For a 50 kWp system in Kent or Essex, this translates to approximately 47,750 kWh of annual generation under the MCS central estimate. At current electricity prices, that generation is worth approximately £13,227 per year in avoided costs and export income combined.
Generation varies across the year as expected, with peak output in May, June and July and reduced output in November, December and January. However, even the winter months generate meaningful electricity:
| Season | Approximate monthly generation (50 kWp) | % of annual total |
|---|---|---|
| Summer (Jun–Aug) | ~5,500 kWh/month | ~35% |
| Spring / Autumn (Mar–May, Sep–Nov) | ~3,500 kWh/month | ~44% |
| Winter (Dec–Feb) | ~1,200 kWh/month | ~8% |
A well-designed system matches system size to consumption profile — ensuring that summer surplus is balanced against winter shortfall and that self-consumption is maximised across the full year.
Panel quality matters over a 25-year asset life. GreenBulb Energy specifies exclusively BloombergNEF Tier 1 panels — specifically the Astronergy N-Type TOPCon monocrystalline bifacial series. Astronergy is a subsidiary of CHINT Group, one of the world's largest electrical equipment manufacturers.
The independent evidence for Astronergy's panel quality is specific and verifiable:
A commercial solar installation involves three layers of warranty protection. Understanding each layer is important for assessing the risk profile of the investment:
Not all solar installers carry the same level of certification. GreenBulb Energy holds a combination of accreditations held by only a small minority of UK solar installers:
For businesses that require certainty over their generation figures — for lender requirements, board approval processes or specific cash-flow commitments — production guarantee insurance is available through specialist renewable energy insurers.
This covers shortfalls in generation caused by lower-than-expected irradiance or unusual weather patterns, compensating the business if the system generates less than the projected MCS estimate in a given year.
For a 50 kWp commercial system, the annual premium is typically in the region of £2,500–£3,500 plus Insurance Premium Tax, underwritten by A-rated security. This is an optional additional cost — most commercial clients find the combination of the MCS central estimate, 30-year panel performance guarantee and independent accreditation provides sufficient confidence. For specific situations where contractual certainty is required, it is available.
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