By how much will my electricity bill reduce if I install a wind turbine?

It is impossible for a manufacturer of a turbine to predict that installing one of their machines will reduce bills by, say, 30%. Every customer's total demand and profile is different. It is worth mentioning that generating your own electricity will reduce the energy payment portion of your bill (kWh or units) but it will not have an effect on the standing charges portion of your bill if you remain grid connected.

Depending on the quality of the turbine and the suitability of the site a 3kW turbine could produce, in excellent conditions, the average number of units a domestic customer consumes in a year (4,000 - 6,000 kWh). If the timing of the demand for power in the house exactly matches its generation then bills will be greatly reduced and only standing charges will remain outstanding. In fact if the demand matched the generation exactly (which is almost impossible with an intermittent energy source like wind) it would be possible to remove or disconnect the grid connection.

At the other extreme we could look at the example of a rugby club with electric showers and flood lights. The load factor of such an electricity customer would be very low. Load factor in this context refers to the ratio of average load to peak load over the year. Peak load might occur for 2 hours during each night of mid week winter training under lights on 2 nights per week totalling around 150 - 200 hours out of 8760 in a year. Matching the wind resource to this type of demand is impossible without significant battery storage. In the absence of storage the turbine might be producing 10 times the annual demand of the site but just not at the right time. By accessing an export tariff the economics can be improved in these types of situations but it should be remembered that only the first 3,000 kWh exported can avail of an 19c/kWh tariff. Each unit exported thereafter will receive 9c/kWh. And this only applies to domestic customers initially.

In reality the efficacy of a turbine in reducing bills can only be known with retrospective analysis. However, with a thorough resource assessment, site assessment and accurate, independently certified manufacturer performance parameters it is possible to estimate a range within which the turbine should perform. Consumers should research carefully the organisation providing the test reports. Only accredited test labs should be given credence as anyone can print a convincing certificate.