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Annual operating costs of a 1.5 MW wind turbine are relatively low compared with those of a hydro generating plant of about the same size, but more than those of a 1 MW photovoltaic plant. Specific average investment costs of wind energy, however, are only about a quarter of those in both hydro and photovoltaic plant. Hydro produces more power, though. Annual generation per kilowatt of installed wind power is at best only about half of that of hydro, while photovoltaic generates only about half as much as wind.

These and further comparisons between the renewable energy technologies have been made possible following the recent release of a report by Germany's Federal Ministry for Education, Science, Technology and Research. The figures for renewables contained in the report have been compiled from renewable energy organisations and disparate literature.

The source of the operating costs figures for wind, however, adds a complicating factor. These have been gathered according to criteria set by the economy ministry. It takes the annual operating costs of turbines as quoted by the operators, but subtracts the no-claims bonus paid to operators by their insurance companies when no damage or failure to their machines has occurred. The research ministry would have preferred to have used figures collected through its empirical experience of 1500 turbines monitored under its 250 MW wind energy support program. This registers average investment costs for wind of about DEM 2000/kW, regardless of the size of turbine, and quotes operating costs at 3.5% of the investment sum. The resulting annual operating cost is about DEM 70/kW -- nearly double that calculated from the economy ministry figures.

In its report, the research ministry ignores this dilemma, instead providing figures for annual pay back rates over ten, 15 and 20 year periods at different rates of interest. The unwritten message is "do it yourself."

The data show that the capital costs of hydro, wind and photovoltaic plant all decline with increasing size (figure 1). Hydro and PV costs both reduce by about one-third between the smallest and largest plant sizes. The range of sizes quoted for wind, however, is much less -- from 270 kW to 1500 kW. Whereas the annual operating costs for hydro and PV decrease with increasing size, wind operating costs increase by over 50% between the upper and lower range (figure 2). This increase, however, is offset by significantly higher energy productivity from the MW size machines.

A 15 year depreciation period and 8% real interest rate are fairly typical for the whole of Europe and are a fair basis for calculating electricity prices shown (figure 3), though in Germany loan repayment periods are shorter, resulting in higher electricity prices. For wind, electricity generation costs fall by around 10% between the size ranges 270 to 1500 kW. The comparison shows that wind prices are around half those of hydro and less than one-tenth of PV electricity costs. The high cost of PV is partly due to the high capital cost and partly to the low capacity factors, which are around 10%.

The information on costs is contained in a two page transcript of tables prepared in answer to a parliamentary question and printed in the Bundestag-Drucksache BT. The tables were compiled by Department 412 at the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie in Bonn.