Electric & Gas Hydronic Boilers

AHHAC supplies and installs both electric hydronic boilers and gas hydronic boilers for Sydney and Australia-wide hydronic systems. A hydronic boiler heats water that's circulated through your home to radiators, underfloor in-floor heat pipework or fan coils — and (on system / combi units) typically supplies domestic hot water for taps and showers. Modern condensing gas units run at 90–98% net efficiency; electric hydronic boilers run at 99–100% conversion efficiency with zero combustion on site.

Our full premium hydronic boiler range covers electric in-floor heat boilers (Heatrae Sadia Amptec, Thermoflow, Stiebel Eltron, Slim Jim), and gas hydronic boilers from Viessmann, Sime, Bosch, Vaillant, Worcester, Rinnai, Rheem, Baxi and Immergas — sized from 6 kW (small electric apartment systems and slab heating) up to 200+ kW cascade systems (hotels, schools, multi-unit residential, commercial fit-outs).

Electric hydronic boilers for in-floor heat — when they make sense

An electric hydronic boiler is the quietest, simplest hydronic heat source you can install. No combustion, no flue, no gas connection — just a wall-hung electric unit (8–24 kW typical) that heats water for the hydronic loop. Perfect for Sydney apartments and townhouses without gas connections, granny flats, off-grid sites, and homes pursuing all-electric / Net Zero builds. The electric boiler runs at near-100% conversion efficiency — every kWh of electricity becomes a kWh of heat.

The trade-off is running cost. At Australian residential electricity tariffs an electric hydronic boiler is roughly 2–3× the running cost of a heat pump hydronic system. So AHHAC's recommendation is: electric boiler for tight-space apartments where a heat pump can't fit, OR for new builds with serious rooftop solar PV (the array effectively pays the running cost). For everywhere else, a heat pump hydronic system is the smarter spend.

We supply and install: Heatrae Sadia Amptec (UK, single-phase 4.5–14.4 kW, 3-phase up to 24 kW), Thermoflow EWA range, Stiebel Eltron RDW (3-phase 12–36 kW for larger sites), and the Slim Jim electric hydronic boiler range. All carry digital flow-temperature controllers, weather compensation inputs, and OpenTherm modulating controls.

Why condensing boilers are the standard today

Traditional non-condensing boilers ran at 75–80% efficiency — they wasted up to a quarter of the gas they burned. Modern condensing boilers recover the latent heat in the flue gases by cooling the flue water below dew point, turning that lost energy back into useful heat. The result is 92–98% net seasonal efficiency on most modern Australian installs.

The catch: condensing only works when the return water temperature is below ~55 °C. That's a poor match for old high-temperature radiator systems, but it's perfect for underfloor heating (35–45 °C), modern oversized radiators, and any hydronic system that's been designed for low-temperature operation. We size every system at design stage to maximise condensing operation.

System boiler vs combi boiler — which to specify

A system boiler heats your central heating circuit and feeds a separate hot water cylinder (typically 150–300 L). It gives you stored hot water that multiple outlets can draw from simultaneously without flow drop — ideal for family homes, anywhere with multiple bathrooms, or where you want a recirculating loop.

A combi (combination) boiler does both jobs from one unit, heating water on demand for taps and showers without a cylinder. Saves cupboard space and works well for apartments, townhouses and smaller homes with one bathroom — but flow rate caps how many outlets can run at once, and very long shower runs can dip in temperature.

For larger Australian homes with 2+ bathrooms, AHHAC almost always specifies a system boiler with a thermal store or DHW cylinder — the comfort difference is significant. For compact dwellings, a combi is the cleaner solution.

Floor-standing & cascade systems for commercial

Above ~70 kW heat demand we move from wall-hung to floor-standing units, or cascade two-to-six wall-hung modules in series. Cascading is the modern preference — it means each individual module runs in its most efficient band, and the system has built-in redundancy (one module out for service doesn't drop the whole site). We design cascade systems for hotels, schools, aged-care facilities and multi-unit residential builds.

Smart controls & weather compensation

A modern boiler with a thermostat that just clicks on/off wastes 10–15% of the gas it burns. Weather compensation reads outside temperature and modulates the flow temperature to match heat loss — milder days run cooler flow, much colder days run hotter — keeping the boiler in its sweet spot. AHHAC fits weather-compensated controls on every install where the boiler supports it (Viessmann Vitotronic, Bosch EMS, Vaillant ecoTEC, Rinnai SmartStart).

For per-room programming we add a multi-zone controller (we like MAXA's thermostat range), and for smart-home integration we expose the boiler over OpenTherm or Wi-Fi so the system pairs with Google Home, Apple HomeKit and Alexa.

Service, warranty and running costs

Modern boilers carry 2–5 year manufacturer warranty as standard — extendable to 7–10 years with annual servicing through an authorised installer. AHHAC handles registration and offers annual service contracts that maintain warranty validity. Typical service interval is 12 months; expected boiler life is 10–18 years (longer for the better European brands when annually serviced).

Sime recommend twice-yearly maintenance on the Brava Slim 30 BFR to maintain warranty cover — AHHAC includes both visits in our annual service contract. Running cost on natural gas in Australia (2026 averages): a 200 m² home running hydronic heating + DHW typically uses 18,000–28,000 MJ per year — roughly $700–$1,250 in gas at current tariffs. Switching from electric storage hot water to a gas combi typically pays back in 4–6 years on hot water alone.

Featured product: Sime Brava Slim 30 BFR

The Sime Brava Slim 30 BFR is an Italian-engineered low-temperature wall-hung gas boiler distributed in Australia by Reece. It's a heating-only unit (no DHW production) — designed to drive hydronic radiators, underfloor and skirting heating with a separate hot water cylinder. Two variants: 30 BFRi for internal installation (Reece code 8112540) and 30 BFRe specifically engineered for outdoor installation (Reece code 8112541, IP X5D rated for atmospheric exposure).

Headline specs: nominal heat output 28.1 kW, modulating down to 13.1 kW on natural gas or 9.2 kW on universal LPG. Maximum useful efficiency 93.7%, minimum 87.3%. NOx Class 5 (< 70 mg/kWh) — ultra-low-emission certified. Heating temperature adjustable 20–80 °C. Maximum operating pressure 3.0 bar (300 kPa) with 9 L total / 5 L useful expansion vessel and a 3-bar safety relief valve.

Compliant with AS/NZS 5601 (Gas Installations), AS/NZS 3500 (Water Services) and AS/NZS 3000 (Electrical Installations). SAI Global certified under licence SAI-400197 to AS/NZS 4552 Gas Safety. Control includes microprocessor electronic board with OpenTherm-compatible remote control input, climatic curve operation with external sensor (boiler temperature varies based on outside temperature for significant energy savings), anti-freeze function, anti-blocking pump cycle every 24 hours, and a 15-minute chimney-sweep mode for combustion measurement.

Key benefits

• Electric hydronic boiler and gas hydronic boiler — Sydney & nationwide
• Electric in-floor heat boilers — 6–36 kW, 99% conversion efficiency
• Gas condensing boilers — 92–98% seasonal efficiency
• Wall-hung, floor-standing and cascade options
• 18 kW residential to 200+ kW commercial
• Combi (no tank) or System (with DHW cylinder) configurations
• OpenTherm modulation matched to demand
• Weather-compensated control as standard
• BMS-compatible models for hotels, schools, hospitals
• Smart-home pairing via Wi-Fi gateway
• Up to 10-year extended warranty with annual servicing
• MAXA thermostats for per-room scheduling
• STC and gas-rebate eligibility on most upgrades
• Replacement of old systems typically 1–2 days