Overview
Turlough Hill (Irish: Tomaneena) rises to 708 m (2,326 ft) in the heart of the Wicklow Mountains, ranking as the 136th highest summit in Ireland. The peak is defined by two contrasting features: a rugged, wind-swept granite ridge draped in blanket bog, and the sleek, geometric lines of an artificial reservoir perched near the top. This is the site of Ireland’s only pumped-storage hydroelectric power station, a mid-20th-century engineering project that quietly powers homes across the country while remaining largely hidden beneath the mountain’s natural cover.
For visitors, the hill offers a well-marked circuit that combines moorland hiking, glacial geology, and panoramic sightlines. On clear days, the view stretches from the coastal cliffs of the Irish Sea to the neighbouring summits of Camaderry and Conavalla, with the glacial corrie lake of Lough Nahanagan sitting in the valley below.
The Name & History
Long before concrete and turbines were brought to the summit, the hill was known locally as Tomaneena. The name Turlough Hill was assigned in the 1960s by ESB engineer J. O’Riordan, who named it after his son during the initial site surveys. The similarity to the Irish word turlach (a seasonal lake that fills and dries on limestone bedrock) is purely coincidental, though it has given the mountain a distinctive geographical ring.
When the Electricity Supply Board began planning a pumped-storage scheme in the mid-1960s, preserving the dramatic vista at the Wicklow Gap was a priority. The ESB hired landscape architect Sylvia Crowe, who advised planting vegetation on the reservoir’s embankments to blend the structure into the surrounding moorland. To further protect the view, the transmission lines were buried underground for roughly one mile before emerging on pylons further down the King’s River valley. This decision added significantly to the project’s cost, but it ensured the mountain’s skyline remained largely untouched.
The Power Station Beneath the Mountain
Construction on the Turlough Hill scheme began in 1968 and concluded in 1974, making it the largest civil engineering project Ireland had undertaken at the time. The plant operates on a simple but highly effective principle: during periods of low electricity demand, surplus power pumps water from the natural Lough Nahanagan up to the artificial upper reservoir. When demand spikes, gravity does the rest. The water rushes back down through pressure tunnels, spinning four reversible pump-turbines housed in a cavern measuring 76 × 21 × 27 metres inside the granite mountain.
The facility can generate up to 292 MW of electricity and is designed for rapid response, moving from standstill to full output in just 70 seconds. With a storage capacity of over 1,590 megawatt-hours, a full upper reservoir can run the plant at maximum load for more than five hours. Since 2004, Turlough Hill has also served as the Hydro Control Centre for the ESB’s entire hydroelectric portfolio. In 2024, the station celebrated its 50th anniversary since commissioning in 1974, marking the milestone with special public tours during National Heritage Week and photographic exhibitions. It remains a key educational site for technical groups, hosting tours such as the early 2026 Techies Tour.
Guided tours of the power station are available through the ESB on a pre-booking basis. The free visits cover the control room, surge tank, and penstock, and include a short walk around the reservoir perimeter where interpretive panels detail the engineering and environmental safeguards built into the scheme.
Walking Turlough Hill
The most popular route is a 4.7-mile (7.5 km) circular walk that typically takes three to four hours. Starting from the car park at the top of the Wicklow Gap, the path heads south toward Lough Nahanagan before climbing to the summit of Camaderry (698 m). From there, the trail loops through the Sevenchurches cairn field – a cluster of ancient stone markers – before descending toward the Turlough Hill reservoir. The final push climbs westward to the true summit, where the access road and transmission infrastructure give way to open bog and sweeping views.
What to look out for on the trail:
- Glacial features: Lough Nahanagan is a classic corrie lake, carved by ice during the last glacial period and now serving as the scheme’s lower reservoir.
- Alpine flora: Despite its relatively low elevation, the exposed ridges support plants typically found at higher latitudes. Keep an eye out for dwarf willow, cowberry, crowberry, fir clubmoss, and common bilberry growing alongside heather, purple moor-grass, and Sphagnum moss.
- Trail conditions: The path is well-signposted, but sections across the bog can be soft and uneven. Sturdy footwear with good ankle support is essential, especially after rain.
Practical Information
- Access: A tarmac road runs from the Wicklow Gap car park directly to the summit area. The road is open to pedestrians and cyclists, and you can park at the gap for free.
- Best time to visit: Spring through autumn offers the most stable weather and vibrant moorland colouring. The summit can be exposed to strong winds and sudden cloud cover year-round, so always check the forecast and pack layered, waterproof clothing.
- Preparation: Carry a map or download a GPX file, bring sufficient water and snacks, and follow Leave No Trace principles. The boggy terrain and lack of mobile signal in places mean it’s wise to inform someone of your route and expected return time.
- Tours: ESB guided tours of the power station are free but require advance booking. Spaces are limited, so check the ESB website early in the season.
- Nearby stops: The Glendalough monastic site and lakes are a short drive south, while the village of Avoca offers pubs and cafés for a post-hike meal. The Wicklow Way long-distance trail passes through the area, and the Barrow Way begins further south for those planning extended river-valley treks.
Book your ESB tour a few weeks ahead if you want to see the generator hall, and start your walk early in the morning to avoid the midday mist that frequently settles over the gap.