The Whichgreen Method

We've been compiling the statistics behind this Rating table, and publishing them since 2004. Here's how we assemble the information.

Whichgreen Statistics – Methodology 2004 to 2014

Since 2004 we’ve published figures for each energy supplier in the UK,showing their annual spend, per customer, on new sources of green electricity. We expressed the annual spend as £s per customer – it is a per capita measure of spending on new sources of renewable energy.

Here’s how the figures are arrived at:

1. The figures are for calendar years.

2. Each year, we identify new sources of renewable energy built in the UK (we often refer to this as New Capacity). We identify those from Wind, Hydro, Biomass & Solar PV sources – which are over 50kW in capacity, using OFGEM and Renewable UK  data.

3. We only include New Capacity in our calculations. Where existing sites (generators) have been repowered only the increase in net capacity (the New Capacity over and above the pre existing) is taken into account and the Build Cost is proportionally attributed. Sites that were refurbished, but with no increase in total capacity, are not included in the figures, because no New Capacity had resulted.

4. Where the cost of building new projects (the Build Costs) are available within the public domain (eg via press releases) these are used in our calculations.

5. For all other New Capacity the Build Cost is calculated based upon the installed capacity of the project multiplied by the generic costs per installed MW as published in the Enviros Consulting report "The Costs of Supplying Renewable Energy" and the Mott MacDonald report "UK Electricity Generation Costs Update" (available on the DECC website1&/2).

6. Domestic electricity customer numbers for each supplier are obtained from OFGEM3 or from material released by the suppliers themselves.

7. The spend per customer figure (or £ per customer) – for each supplier in the UK – is calculated by dividing the Build Cost (from 4 and/or 5 above) of the New Capacity, by the number of domestic customers (from 6 above), it's as simple as that.

8. Once compiled, the relevant information (New Capacity, total Build Cost, total number of customers and the resulting £ per customer figure) is sent to each individual supplier to allow them to verify the assumptions, or indeed correct them if public data is superseded by data that they themselves hold. Suppliers are given two weeks to respond after which the figures are published.

We now represent the spending figures in a graphical presentation – an A to G chart that we’re all used to seeing to rate white goods (for energy efficiency) and cars (for fuel efficiency).

The other change we’ve made is to present the data as a long term average, rather than an end of year snapshot.

We introduced that change following some fairly consistent complaints from the Big 6 energy companies (British Gas particularly) who felt we were overlooking the projects they’re intending to build 'soon' and renewable energy project stake time to get off the drawing board (as if we didn't know that). Developing renewable energy projects does take time of course. So by using a long term average we smooth the years (good and bad) and, eventually we hope, the promises come good and find their way into the figures.

9. The final part is the drawing of the thin dotted blue line.

We draw it at the boundary between Category E and F – at £32. This represents the average annual level of spending required of all suppliers to meet the annual growth component of the Renewables Obligation (RO). Not the total RO target in any given year, just the amount of increase, the incremental growth required by the RO. This is the amount needed to be spent to avoid falling (further in most cases) behind the RO – it’s the basic ‘keep up’ minimum.

10. To calculate this – we start with DECC figures for the average number of units (kWhs) of electricity that households in the UK use – in any given year4.We also know the annual incremental growth of the RO for any given year, as published by OFGEM.

Renewables Obligation – % Rise 2004 to 2014

  2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
% Rise on Previous Year 1.3 0.6 0.6 1.2 1.2 1.2 0.6 1.4 1.3 3.4 4.8

From these two figures we can calculate the number of units of green electricity that need to be generated to meet the incremental growth of the RO.

Knowing the number of units required to be generated (to meet incremental growth) we can ascertain the installed capacity (New Capacity) required to generate that. We base that calculation on new onshore wind capacity (using standard load factors). We do this as it gives the cheapest cost of all technologies per unit generated – and gives the smallest sum required to be spent. We multiply the New Capacity required (to be built) by the average Build Cost per MW. And hey presto, we have the cost in pounds per year required to meet the incremental RO target. In 2014 this figure was £32 per customer.

Average Annual Expenditure on Building New Sources of Renewables 2004 to 2014 (expressed as pounds per customer)

  £ per Customer
Ecotricity £252.38
Good Energy £64.26
NPower £63.65
Scottish Power £63.40
SSE £48.85
E.On £27.18
EDF Energy £19.10
Centrica £12.08
Green Energy UK £0.00
Co-Op Energy £0.00
Ovo £0.00

1 The Costs of Supplying Renewable Energy

2 Mott MacDonald, 2010, UK Electricity Generation Costs Update

3 Energy Supply Probe - Initial Findings Report

4 DECC. Digest of UK Energy Statistics. Chapter 5 Table 5B Domestic Sector Sales / Domestic Customers = average domestic consumption)