- The “global” wind power load factor is estimated to be 22.7% for 2012. This is based on an analysis of installed wind capacity and electricity production data for 17 countries published by BP . This estimate is subject to the veracity of the data and methodology applied. The average load factor for the last 9 years is estimated to be 22.5±0.4% (1SD).
- A number of competing factors are expected to impinge upon wind load factors over time, such as improving turbine efficiency, the move to less windy onshore sites, the move to windier offshore sites, increasing down time of ageing turbines and climate change. Since 1997 average loads have increased (Figure 1) but have changed little in the last 9 years suggesting that positive and negative factors are in balance.
Figure 1 The average load factor in dark blue for the 17 countries listed in Figure 2. Overall load factors have improved with time but in detail have been static for the last 9 years.
BP report installed wind capacity at the end of the year but electricity production for the full year . Since all new capacity built in a given year has not been operational for the full year an adjustment is required, especially when capacity growth is high. The capacity figure used here in any given year is equal to the year end capacity of the previous year plus half of the capacity addition in the given year. This is imperfect but should result in negligible errors where new capacity additions are small.
Seventeen countries with significant installed wind capacity were selected (Figure 2). Brazil was originally in the mix but the data were rather chaotic so the country was removed. Back in 1997 there was not too much to distinguish the pack (Figure 2). Germany was first to lift off followed by the USA and Spain. There are 5 major players: China, USA, Germany, Spain and India. The UK is in a distant sixth place. Each of these 5 countries are energy importers and 4 of them, China, Germany, Spain and India may be described as enthusiastic to boost indigenous primary energy production although they will all claim their motive is to reduce CO2 emissions.
It is the USA and China that catch the eye. The worlds number one and number two economies with highest CO2 emissions seem Hell bent on winning the wind turbine installation race.
Figure 2 The history of wind capacity expansion in 17 selected countries.
Figure 3 Load factors for the 17 countries shown in Figure 2 calculated using adjusted capacity as descried in Methodology above. As capacity has grown load variability has declined to the point that in most countries loads have been quite uniform for the past 5 years. The 5 year averages are shown in Figure 4. New Zealand stands out as an anomaly. New Zealand has only 603 MW installed capacity (China 68892 MW) and is therefore a very small player along with Egypt (552 MW). It is plausible that a small number of turbines deployed in a windy site may yield a load factor of 40%.
Figure 4 The histogram shows the average loads for the last 5 years. Wind loads vary from 16.3% in China and 18.3% in Germany to 29.8% in the USA and 30.2% in Australia. All of the data are subject to the uncertainty of the input data  and the methodology applied. It is surprising to see that the USA has almost double the load factor of China. In the year 2000 American and Chinese loads were similar (Figure 6). Since then, USA loads have grown, which if true points to an industry getting more efficient while in China loads took a strange step down in 2007, the year that exponential capacity growth began. It is possible that in China State edict means that turbines are being installed anywhere and everywhere.
Figure 5 The data plotted in Figure 4. I’d be interested to hear from commenters how these results compare with national statistics. Note that the data show 5 year means, 2008 to 2012. For the UK in 2012, DECC report 35.2% for offshore wind and 26.2% for onshore wind. In 2012, my figure for the whole UK is 30.8% suggesting that the methodology is sound.
Figure 6 Comparison of loads between the USA and China. At face value the US wind industry is growing more efficient while the Chinese industry less so.
The range in wind load factors between countries is roughly 2 fold while for solar it is at least 3 fold . Furthermore, wind likely has a higher ERoEI than solar making it less sensitive to load for embedded energy recovery. This makes wind a more widely deployable renewable energy source. It still makes more sense nevertheless to deploy wind on windy sites in windy countries.
A global average load factor of 22.5% may seem good news for the wind industry but it must be born in mind that nuclear runs with a load factor closer to 90%. The low load factor of wind is a feature of its intermittency and the key arguments against wind power discussed in “Arguments for and against wind power” remain .
 BP: Statistical Review of World Energy 2013
 DECC Regional Renewable Statistics
 Energy Matters The efficiency of solar photovoltaics
 Energy Matters The Arguments For and Against Wind Power