💡 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 →
Solar thermal + heat pump in one cylinder — free hot water from both sources
The Joule Cyclone Solar HP is the correct cylinder when you are installing both an air-to-water heat pump and solar thermal collectors. The lower secondary coil (2.0 m²) connects solar thermal panels and preheats the lower volume of the cylinder using free solar energy. The upper primary coil (3.2 m²) connects the heat pump, which tops up the remaining temperature to the setpoint. On a good Irish solar day, the solar thermal coil provides 60–70% of the day's hot water — the heat pump covers the remainder at high efficiency. At 300L, the larger capacity accommodates both energy sources without conflict. SEAI Solar Water Heating grants may apply to the solar thermal component.
300L3.2m² HP coil25-yr warrantyCopperVented🇮🇪 Made in Ireland☀️ Solar thermal coil includedSEAI: part of HP grant
⚙️ Specifications
Capacity
300 litres
Primary (HP) coil area
3.2 m²
Secondary (solar) coil area
2 m²
Cylinder type
Vented (gravity-fed cold tank)
Inner material
Copper
Insulation thickness
80 mm
Standing heat loss
1.82 kWh/24h
Max primary temp
80°C
Immersion heaters
2 × 3 kW
Dimensions (H × Ø)
1740 × 595 mm
Weight (empty)
66 kg
Warranty
25 years
Made in Ireland
✅ Yes — Irish manufactured
💰 Pricing & SEAI grant
Cylinder supply price
~€980
Plus installation labour ~€400–€700 · Total installed ~€1,530
💰 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
☀️
Solar + heat pump — maximum free hot water
In Ireland, solar thermal collectors generate significant free heat from March to October. Combined with a heat pump, you can achieve near-zero energy cost for hot water from spring through autumn. The dual coil separates the two heat sources so they work in harmony without either blocking the other
💰
Two SEAI grants may apply
The solar thermal coil component may qualify for the SEAI Solar Water Heating Grant (up to €1,200 for evacuated tube collectors). The heat pump system grant covers the HP component. Check current eligibility at seai.ie — always apply before work begins
🇮🇪
Joule Waterford — 25 years, Irish manufacture
Joule manufactures the Solar HP range in Waterford to the same 25-year warranty standard as the rest of the Cyclone range
🏠 Suitable for
Solar thermal + heat pump combinationNew buildLarge familiesMaximum renewable hot water
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
Dual coil — solar thermal preheats, heat pump tops up. Maximum free hot water
SEAI Solar Water Heating Grant (up to €1,200) may apply to solar thermal coil
3.2 m² HP primary coil — fully sized for heat pump temperatures
300L capacity — appropriate for households combining both technologies
Irish-made in Waterford — 25-year warranty
80mm insulation — important for larger capacity cylinders with higher standing loss
⚠️ Worth knowing
300L is large — ensure adequate floor space and structural support before ordering
Requires solar thermal panel installation in addition to heat pump — higher total system cost
More complex installation — two primary circuits to connect and commission
1.82 kWh/24h standing heat loss — higher than smaller cylinders due to increased surface area
🌡️ Compatible heat pump brands
The Cyclone Solar HP 300L 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 secondary coil on this cylinder is designed for solar thermal (flat plate or evacuated tube) collectors. The SEAI Solar Water Heating Grant (up to €1,200 for evacuated tube systems) may also apply to the solar thermal component. Always verify current eligibility at seai.ie.
❓ Questions about the Cyclone Solar HP 300L
The Joule Cyclone Solar HP 300L cylinder itself costs approximately ~€980. Installation (remove existing cylinder, connect to heat pump primary circuit, commission immersion backup) adds approximately €400–€700. Total installed cost: typically ~€1,530. 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 Solar HP 300L has a 3.2 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 Solar HP 300L's ~€980 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 Solar HP 300L 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 Solar HP 300L'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 Solar HP 300L at 300L is a large-capacity cylinder suited to families of 4+ or homes combining both heat pump and solar thermal. 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 Solar HP 300L'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.
No — the Joule Cyclone Solar HP 300L's upper primary coil can operate solely with a heat pump; the lower solar secondary coil (2 m²) is optional. You can install the cylinder now with just the heat pump and add solar thermal collectors later — the secondary coil is ready and waiting. When you do add solar thermal: the lower coil preheats the bottom of the cylinder using free solar energy; the heat pump tops up to your setpoint. On a good Irish solar day from April to September, solar thermal covers 60–70% of daily hot water — the heat pump handles the rest. The additional capital cost of solar thermal panels (€2,000–3,500 installed) needs to be weighed against savings for your household size.
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 Solar HP 300L 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 Solar HP 300L's 3.2 m² primary coil — one of the largest available — 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.
Not necessarily — most Irish homes with air source heat pumps use the heat pump for both space heating and hot water without solar thermal. Air source heat pumps produce domestic hot water efficiently year-round, even in winter. Solar thermal provides additional free hot water from solar energy — it makes most economic sense if you have high hot water demand (large family, frequent showers) or if you are optimising to minimise any residual electricity cost. The additional capital cost of solar thermal panels (~€2,000–3,500 installed) and the more complex dual-coil system needs to be balanced against the savings. Discuss with your installer whether the payback makes sense for your specific household.
Yes — if your existing cylinder is a dual-coil solar HP cylinder (like the Joule Cyclone Solar HP), you can add solar thermal collectors later by connecting them to the secondary coil. If your existing cylinder is a single-coil heat pump cylinder, you would need to replace the cylinder to add solar thermal. When installing a new heat pump, specifying a dual-coil cylinder from the outset is a low-cost way to future-proof for solar thermal — the price difference between a single and dual coil cylinder is typically only €150–200.
Get it installed
Find SEAI-registered heat pump installers for the Joule Cyclone Solar HP 300L
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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Up to 3 SEAI-registered installers in your area will contact you within 1 business day with system recommendations and pricing — including the Joule Cyclone Solar HP 300L cylinder.
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De Energy Hub
More power to youTM.
🏡 Built for holiday lets, Airbnb hosts & short-term rental
Guest EV charging — automated, no host involvement required
Holiday home and short-term let owners with a heat pump and EV charger can offer guest charging on Pure Energy — fully automated. Set up once, generate a QR code, and let guests book, check in and check out without any host involvement. Include complimentary charging as a listing USP or set a per-session charge.
☀️ Pure Energy🔄 Smart Energy🚀 Boost Energy
📱
Zero host involvement
Guests book, check in and check out via the app — you receive notifications without lifting a finger
🌿
Pure Energy as a USP
Market your property as offering 100% renewable-powered EV charging — increasingly sought after on Airbnb
🎟️
Free or paid — your choice
Set charging free with a promo code, or earn per session — toggle any time from the host dashboard
The Joule Cyclone Solar HP 300L 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 both a heat pump primary coil and a solar thermal secondary coil. If you have solar PV panels rather than solar thermal collectors, a solar diverter redirects surplus solar electricity directly to the immersion heater in this cylinder — giving you free hot water from your solar panels without any plumbing changes.
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 →
