Home power generation in Northern Ireland

From Jonathan's Reference Pages

I decided to investigate the cost-effectiveness of generating your own power from renewable source (wind and solar) in Northern Ireland.

The basics

A power generator's output is measured in kilowatts (kW), or units of 1,000 watts. One unit of electricity is equivalent to one kilowatt-hour (kWh), or the amount of energy produced by a one-kilowatt generator in one hour. Northern Ireland's electricity supplier, NIE Energy, currently charges 15.03p per unit.

You can, however, generate your own electricity and any surplus back to the grid. With renewable sources (wind/solar), your running costs are almost zero (assuming nothing breaks down), so the only issue is whether or not you will recoup your initial cost, and how soon.

NIE Energy Generation Tariff

NIE currently offers 5.22p per unit generated.

In addition, generating electricity from renewable sources entitles you to Renewable Obligation Certificates from electricity regulator OFGEM, which NIE will currently buy from you for 8.32p per unit generated. You receive these whether you use the generated electricity yourself or sell it.

Therefore, each unit you sell currently pays 13.54p, while each unit you use yourself saves 15.03p and earns 8.32p for a total of 23.35p.

Solar cost-effectiveness

The European Commission Joint Research Centre estimates that Northern Ireland receives sufficient sunlight for a 1kW solar panel to generate between 700 and 1,000 kilowatt-hours per year, depending on location and optimal positioning (see optimum positioning chart, sub-optimal positoning chart). An NIE case study (PDF) in Carrickfergus estimates 900 kilowatt-hours.

For each 1kW of solar panel installed, you will receive around £94.78 to £135.40 per year if all power is sold, and earn/save £163.45 to £233.50 per year if all power is used. Since you'll probably use some and sell some, the result will probably be somewhere in the middle.

The initial cost will be several thousand pounds, a significant amount of which can be covered by a renewable energy grant. A search of accredited solar panel installers suggests total costs of around £5,000 to 7,000 per kilowatt (peak) depending on size. Grants available from NIE and the Low Carbon Buildings Programme can reduce this to something in the region of £3,000-£3,600 for a 1kW installation, or £5,700-£9,700 for a 2kW installation.

The big question is how soon the system will become cost-effective. A 1kW installation will generate 700 to 1,000 units per year, earning/saving £163.45 to £233.50 per year assuming you use all the energy, and 20% less if you sell half. Given current rates and reasonable installation costs of £3,500, it will take at least fifteen years just to break even on a 1kW installation at current rates, and potentially longer than 20 years.

Increasing the initial investment doesn't provide much help, since energy sent back to the grid is less valuable than energy saved and the grant on initial costs is capped.

Conclusion: Solar power in Northern Ireland isn't cost-effective yet. We have poor solar coverage, initial costs are too high to be cost-effective compared to paying for electricity, and NIE doesn't pay enough for green energy for this to be worth it.

Wind cost-effectiveness

Northern Ireland has some of the best wind speeds in Europe, ranging from 5m/s to 11m/s at a height of 50m, or about 4.4m/s to 9m/s at a height of 10m. This is about on par with Texas which currently generates around 8,000MW from wind power, although admittedly using taller, larger wind towers than you can reasonably site in your back garden. (Source: European Wind Atlas, United States annual average wind power)

Just how much electricity this converts to and what this will cost to install depends on the model of wind turbine used. Straight comparison is difficult since different manufacturers rate their products assuming different wind speeds and many are not up-front about total installed cost. Some rate their device assuming wind speeds much higher than the UK average.

One retailer offers a 2.5kW wind installation which in Northern Ireland would cost £12,500 installed after grants from NIE and the Low Carbon Buildings Programme. At wind speeds of 5m/s (UK average), the manufacturer estimates 3,500 units of electricity per year, which assuming you use half and sell half back to the grid will net £645.56 per year, breaking even in 19 years. A 6kW installation, assuming you can use half of the estimated 9,500 units generated, will cost £18,500 after rebate, earn £1752.275/year, and break even in 10 and a half years.

Things look significantly better if you get high wind, such as a hilly area. A 50% increase in wind speed in will more than double the energy available to the windmill, since the wattage produced is equal to the wind speed times the windmill's blade length squared. An average speed of 7m/s will produce twice as much, so the 2.5kW wind turbine above will pay for itself in 10 years and the 6kW installation in 5 years. Parts of Northern Ireland receiving an average of 9m/s or higher will find it increasingly cost-effective to employ wind turbines at these rates.

Prices currently vary significantly, with one UK supplier (PDF) offering a 6kW installation for around £30,000 installed (£5,000/kW) after Northern Ireland rebate, while another offers a 5kW DIY kit for under £2,800 after rebate (£560/kW), without installation. The options mentioned earlier works out to £3,083 (6kW) and £5,000 (2.5kW) per kilowatt.

Other than price, the major drawbacks to a windmill are that it's pretty big (5.5m to 11m masts are typical), you'll need to apply for planning permission, and the neighbours might complain. Smaller roof-mounted models are available, although their performance is lower. In one test (PDF), a 1.5kW SWIFT Turbine (£3,000 after Northern Ireland rebate, price not including installation) generated 975kWh in Scotland, which has similar or better wind speeds to Northern Ireland. This would earn around £179.84 per year and break even in 17 years.

Conclusion: Wind power has good potential in Northern Ireland, but is most effective in rural areas where wind speeds are high. Build-up areas have poorer wind speed and fewer opportunities for positioning good tall windmills,


Northern Ireland has good wind potential, but rubbish solar. It's not even worth considering solar power until solar panel prices come down, normal electricity prices go way up, NIE starts paying a lot more for green energy, or government subsidies for renewable energy are drastically increased. The best-case payoff for solar is over 10 years.

Wind power can be quite effective in rural hilly areas, but less so in urban ones where wind speeds are lower. Building an 11 metre windmill mast in your back yard is a difficult proposition, and even the best roof-mounted small windmills don't break even for over 15 years.

Further reading

Page created: 27th November 2009