Misleading claims!

The importance of being fully informed about solar generating capacity.

Have you ever achieved the miles per gallon or the Electric Vehicle range claimed by the manufacturer?  Almost certainly not!

The industry’s claims about Solar energy ‘capacity’ are, it seems, also prone to mislead.  Developers currently base their calculations on a theoretical number of homes that might be supplied, and projected CO2 savings, all based on the “nameplate” or “design capacity“ of the generating plant. However, the power rating of a solar PV panel, which makes up the nameplate capacity, is calculated using ‘Standard Test Conditions’ (STC) indoors and under laboratory conditions. STC only match real conditions in the UK for a few days of the year.  The actual outputs for most days are significantly below the STC criteria.

Other factors which also reduce the nameplate capacity are:

  • DC/AC conversion ratio (clipping) – 2-5% loss
  • Invertor efficiencies – 2-5% loss
  • Dirt on panels – 2% loss
  • Year-on-year performance degradation of PV panels – 0.5% loss (over 20 years 10%)

The largest reduction relates to the load factor i.e., the ratio of how much solar electricity is generated as a proportion of the total solar nameplate capacity for any given year.

Taken from the government’s Digest of UK Energy Statistics (DUKES) the load factor for Solar PV in 2022 was 10.2. a reduction of 89.8% of the nameplate capacity.

Taking a real-world example of a proposed solar development of 49.9 MW – where the developer claims 12617 houses will be powered with a saving of 10433 tonnes of CO2 emissions – applying the above factors to these figures shows the true potential of the solar generation development.

                           Claimed                                                                     Real

The actual public benefit in this example is approximately 1156 houses supplied, and not the 12617 houses stated in the design capacity – and 957 Tonnes CO2 a year saved, not 10433.  Overstating the public benefit by over 90%, no matter how welcome the low carbon energy contribution, is misleading and simply wrong.

(BSR claim for the proposed North Dairy Farm development: 49.9 MW “This is equivalent to the annual electrical needs of approx. 13,000 family homes. The anticipated CO2 displacement is around 13,000 tonnes per annum”.)


Developers do not volunteer this ‘real’ information. So, it falls on planning officers, councillors, and the public at large to research the technology and ask the right questions during the planning application process.

If the developer’s overstated claims about the perceived public benefits are left unchallenged, the actual benefits, will not be in the minds of officers and councillors when they consider the merits of a solar application. In some instances, this could lead to inappropriate and ill-considered planning outcomes, based on unreasonably claimed benefits that would never materialise.

A related issue is a misconception that the local community will benefit from the electricity generated by solar development. There is a recent example where a planning committee was told: “This is energy for (two nearby towns), all of it, not a bit of it, all of it”. The reality was that all the electricity generated was distributed to the national grid, for the benefit of communities elsewhere. There was no specific or exclusive electricity supply benefit to the local community. In another case, significant harm to protected rural landscapes was justified to the local community, only for them to find out later that all the energy produced was not available to them as it had been contract ‘pipelined’ to power City of Landon office blocks!

We all have a duty to ensure that decision-makers are well-informed about material planning matters.  Asking the right questions at the right time. This is particularly important for complex generating technologies, and where the impact they will have on valued landscapes and food production can cause significant local harm.

The need to address the climate and ecological emergency has become even more urgent. The war in Ukraine has exacerbated a food and energy/fuel security and supply crisis – and Dorset homes and fields have been lost to fires caused, in part, by climate change. There surely cannot be anyone in the planning process who opposes the switch to low-carbon energy.

National and local planning policies stress the need for renewable low carbon green energy, but they also underline that the change must: “not be at the expense of the environment they are trying to protect.” As the Prime Minister stated at COP27, ‘there can be no solution to climate change without protecting and restoring nature’.

Many thanks to Jan Owen and the Ham Conservation Group (near Creech St Michael)

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