💡 Hot water cylinders work hardest alongside a heat pump — the cylinder stores the heat pump's output for domestic hot water, cutting fossil fuel use to near zero. SEAI grants of up to €1,600 available for hot water cylinders. Apply at seai.ie →
Joule · Heat Pump Indirect · Ireland 2026
Joule Cyclone Slimline HP 200L — Ireland 2026
Space-saving heat pump cylinder — fits where standard cylinders cannot
The Slimline variant of the Joule Cyclone is 55mm narrower in diameter than the standard model — the critical difference for retrofits where the airing cupboard or utility space is narrow. Despite the reduced footprint, it retains a 2.9 m² heat pump coil and 200L capacity, making it suitable for 3–4 bedroom homes. Joule manufacture it in Waterford with the same 25-year warranty as the full-size model. Specified when space is the limiting factor rather than budget.
200L2.9m² HP coil25-yr warrantyCopperVented🇮🇪 Made in IrelandSEAI: part of HP grant
⚙️ Specifications
Capacity
200 litres
Primary (HP) coil area
2.9 m²
Cylinder type
Vented (gravity-fed cold tank)
Inner material
Copper
Insulation thickness
75 mm
Standing heat loss
1.35 kWh/24h
Max primary temp
80°C
Immersion heaters
2 × 3 kW
Dimensions (H × Ø)
1590 × 490 mm
Weight (empty)
44 kg
Warranty
25 years
Made in Ireland
✅ Yes — Irish manufactured
💰 Pricing & SEAI grant
Cylinder supply price
~€620
Plus installation labour ~€400–€700 · Total installed ~€1,170
💰 Covered by SEAI Heat Pump System Grant (3 Feb 2026)
The cylinder is included as part of your overall heat pump installation cost. The SEAI grant covers the total installed system cost — heat pump, cylinder, controls, pipework and labour — up to:
① Heat Pump Equipment Grant€6,500
② Central Heating Upgrade (inc. cylinder)€2,000
③ Renewable Heat Bonus (fossil fuel switch)€4,000
Maximum total grant€12,500
Apply at seai.ie — receive Letter of Offer before installation begins. BER assessment required (€200 SEAI grant). Homes built before 2007 need Technical Assessment (€200). Installer must be SEAI-registered.
Key highlights
📐
490mm diameter — fits tight spaces
The most common reason a Slimline is specified: the airing cupboard in Irish semi-detached homes built in the 1980s–2000s is often not wide enough for a standard cylinder. The Slimline solves this without sacrificing HP performance
🌡️
2.9 m² HP coil — still heat pump optimised
Despite the smaller footprint, Joule maintains a large-area heat pump primary coil — the most important single specification for heat pump performance
🇮🇪
25-year Irish warranty
Same Waterford manufacturing and warranty as the full-size Cyclone Std
Installation note: Vented cylinders require a cold water storage tank (usually in the loft) feeding by gravity. If your home doesn't have a loft tank, discuss with your plumber whether a vented or unvented cylinder is more appropriate for your installation.
✅ What we like
Narrower diameter (490mm vs 545mm) — fits tight retrofits and apartments
Still 2.9 m² HP coil — full heat pump optimisation in a smaller package
Irish-made in Waterford — 25-year warranty
200L capacity — sufficient for a 3–4 bedroom family home
Two immersion heaters for backup and legionella protection
⚠️ Worth knowing
Slightly smaller coil than full-size Cyclone (2.9 m² vs 3.1 m²)
1.35 kWh/24h standing heat loss — slightly higher than standard due to less insulation surface ratio
Slightly higher price per litre than full-size due to smaller production volume
🌡️ Compatible heat pump brands
The Cyclone Slimline HP 200L is compatible with all major air-to-water heat pump brands. See the Heat Pump Directory for full specifications, pricing and SEAI grant details on all 19 heat pumps available in Ireland.
The Joule Cyclone Slimline HP 200L cylinder itself costs approximately ~€620. Installation (remove existing cylinder, connect to heat pump primary circuit, commission immersion backup) adds approximately €400–€700. Total installed cost: typically ~€1,170. This is usually included in the overall heat pump installation quote from your SEAI-registered installer — ask for the cylinder to be itemised on the quote so you can compare against other brands.
In most cases, no — your existing cylinder should be replaced as part of the heat pump installation. Standard cylinders have small primary coils (1.5–2.0 m²) designed for boiler temperatures of 70–80°C. Heat pumps deliver water at 45–55°C and need a much larger coil (typically 2.8–3.4 m²) to transfer adequate heat at the lower temperature. The Joule Cyclone Slimline HP 200L has a 2.9 m² primary coil — specifically sized for heat pump low-temperature operation. Using a standard cylinder with a heat pump results in slow reheat, inefficient operation, and higher running costs.
Yes — the cylinder cost is included within the SEAI Heat Pump System Grant (up to €12,500 for houses switching from fossil fuel heating, from 3 February 2026). The grant is applied to the total installed system cost including heat pump, cylinder, controls, pipework and labour — not as a separate per-component payment. Cylinders are not individually grant-funded as standalone items. A BER assessment is required before the grant can be drawn down, and all work must be carried out by a SEAI-registered contractor. The Joule Cyclone Slimline HP 200L's ~€620 cylinder cost contributes toward the Central Heating Upgrade element of the grant (up to €2,000).
A heat pump cylinder is typically set to 55–60°C to balance legionella risk with heat pump efficiency. Legionella bacteria cannot survive above 60°C. Most heat pump systems include a weekly legionella protection cycle where the immersion heater in the Joule Cyclone Slimline HP 200L raises the full cylinder to 60–70°C. Day-to-day, the heat pump heats the cylinder to the setpoint temperature (often 50–55°C) — a heat pump's COP drops significantly above 55°C. The Joule Cyclone Slimline HP 200L's max primary temperature of 80°C accommodates both routine heat pump operation and legionella protection cycles. Your installer will configure the legionella cycle as part of commissioning.
The Joule Cyclone Slimline HP 200L at 200L is suited to a typical 3–4 bedroom family home. A heat pump heats the cylinder slowly over 2–4 hours (compared to a boiler's rapid reheat) — so the system is usually programmed to heat the cylinder once or twice daily, storing enough hot water for the day's demand. General guideline: allow 40–50 litres per person per day. For a 4-person household with a heat pump: 160–200L minimum. Homes with high shower use or a bath should consider 200–250L.
Copper is the most widely used material for hot water cylinders in Ireland and works perfectly well in most locations. The Joule Cyclone Slimline HP 200L's copper inner is fully compatible with heat pump operation at 45–60°C. Copper becomes less ideal in two situations: hard water areas (Dublin, Kildare, Meath — calcium deposits accelerate internal corrosion over 15–20 years) and coastal properties within 5–10km of the sea (salt air degrades exposed copper fittings). For soft water areas and inland properties, copper is the most cost-effective choice. For hard water or coastal areas, consider the Kingspan Albion Ultrasteel (duplex stainless) or Telford Tempest (stainless 304) instead.
Joule manufacturing in Ireland means parts, warranty support and replacement components are held locally — not shipped from overseas depots with 2–4 week lead times. For a heat pump system that is your primary heating source, a warranty claim requiring a new cylinder should not leave your home without hot water for weeks. Irish-manufactured cylinders also mean shorter supply chains, typically lower logistics-related carbon, and supporting Irish employment. The 25-year warranty on the Joule Cyclone Slimline HP 200L is backed by a local manufacturer — not a foreign subsidiary — giving greater confidence in long-term warranty support.
Heat transfer through a coil depends on temperature difference (ΔT), flow rate, and coil surface area. In a boiler system, ΔT is large (boiler at 75°C, cylinder at 55°C → ΔT = 20°C) — even a small coil transfers heat quickly. In a heat pump system, ΔT is small (HP at 50°C, cylinder at 45°C → ΔT = 5°C). With a small ΔT, you need a much larger coil surface area to transfer the same heat. The Joule Cyclone Slimline HP 200L's 2.9 m² primary coil compensates for the low temperature differential, allowing the heat pump to operate at lower, more efficient flow temperatures without sacrificing reheat time. Standard boiler cylinders typically have only 1.5–2.0 m² coils — using one with a heat pump results in slow reheat and the heat pump working harder and less efficiently.
Measure the internal width of your airing cupboard — you need a minimum of 560mm (490mm cylinder + 35mm each side clearance for plumbing connections and insulation) for the Slimline. For the standard Cyclone, allow 620mm minimum width. Height is rarely the constraint in Irish homes — both cylinders are 1,470–1,590mm tall, and most Irish airing cupboards are full ceiling height. If in doubt, a plumber can measure and confirm before you order.
For a family of 3–4 people with a heat pump, 200L is typically sufficient. A heat pump heats the cylinder slowly over several hours (compared to a boiler's rapid reheat) — so the system is usually programmed to heat the cylinder once or twice daily, storing enough hot water for the day's demand. For families of 5+ or homes with particularly high hot water demand, a 250–300L cylinder is recommended. Your heat pump installer will size the cylinder as part of the overall system design.
Get it installed
Find SEAI-registered heat pump installers for the Joule Cyclone Slimline HP 200L
Your installer will supply and install both the heat pump and the Joule cylinder as a complete SEAI-eligible system. Tell us what combination you need — we match you with up to 3 SEAI-registered installers in your area. Free and no obligation.
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Open your depot to partner fleets — managed EV charging
Truck and van depots can now open their charging infrastructure to visiting partners and contract fleets. Set your energy rate — charge from your heat pump and solar at Pure Energy rates, blend with grid on Smart Energy, or run at full grid speed on Boost Energy. Filter bookings by vehicle category — Car, Van, Truck, Campervan.
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Open your depot to visiting partners with managed booking — track every session
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Live energy usage, cost per session and cumulative depot totals — all in one dashboard
The Joule Cyclone Slimline HP 200L is designed to work with the following heat pumps, solar diverters and smart energy products from our Irish directories.
Solar diverters — use surplus solar for free hot water
This cylinder has an immersion heater — which means it can receive free hot water from surplus solar. A solar diverter intercepts solar surplus before it exports to the grid and redirects it straight to your immersion, typically providing 60–80% of annual hot water from the sun. Payback is usually under 18 months.
A 4kWp solar system generates approximately 3,600 kWh/year in Ireland. With a solar diverter redirecting surplus to this cylinder's immersion heater, you can cover 60–80% of annual hot water energy for free — on top of the heat pump doing the heavy lifting.
EV charger + home battery — run everything on solar
Your heat pump and this cylinder provide low-carbon heating and hot water. Add solar panels, a home battery and an EV charger and you can power your car, your heating and your hot water from the same roof — the combined SEAI grants available reach up to €14,600.
A hot water cylinder upgrade is often the first step in a wider home energy transformation. With a solar diverter filling your cylinder for free during the day, the next natural step is an EV — charged overnight on cheap night-rate electricity or from surplus solar. See all 205+ EVs in the EV Vehicle Directory.
💧 Solar hot water + EV: your whole home running on free energy
☀️ Solar diverter
Free hot water
surplus solar → cylinder
🚗 Smart EV charger
Free driving
surplus solar → your EV
💶 Combined saving
~€3,000/yr
hot water + fuel combined
A myenergi Eddi fills your cylinder with free solar. A myenergi Zappi in Eco+ mode fills your EV with whatever solar is left — both share generation data via the Hub so they never compete. View myenergi Eddi →
