Collage of radiant heating systems
Radiant heating systems

Electric underfloor heating and radiators are becoming more popular with solar power. So this BLOG explores your options including:

  • Electric resistance systems
  • Hydronic heating systems
  • Underfloor systems
  • Radiator panels
  • Convectors

The key points are summarized below:


  • Hydronic systems are a lot more expensive to install but add greater capital value to your home
  • Electric resistance systems are much cheaper to install but a lot more expensive to run, therefore use:
    • With as much solar power as you can
    • As a short-term approach with a hydronic system later
    • For bedrooms with lower set temperatures
    • For bathrooms with short run times

Help reduce global warming:

  • Install solar panels for most of your power
  • Choose green energy for the additional power you need from the Grid
  • Save power:
    • Improve the thermal performance of your house
    • Wear a jumper and lower your thermostat temperatures in winter
    • Use fans and raise your thermostat temperatures in summer
    • Zone off unused spaces
    • Consider heat recovery ventilators

Improve your peace of mind:

  • Electric underfloor heating and radiators give you a cleaner, fresher house:
    • These systems do not stir up dust, airborne pollen and other allergens
    • Better for people with breathing issues such as asthma
  • Electric systems are safe:
    • There are no pilot flames
    • There are no gas leaks to worry about
  • Lower panel temperatures to 60 degrees:
    • Check this against your heat load
    • Will not scald, safer for small children
    • Better for furniture and window coverings
    • Easier for a heat pump, hence lower running costs

Compared with ducted systems:

  • Reduces building costs
  • Enables higher ceiling heights
  • Avoids the need for bulkheads

Your choices:

Read below for a summary of the systems that you can choose, or mix and match. Both electric resistance and hydronic systems can be installed as:

  • Underfloor radiant systems
  • Radiator panels
  • Convectors
Hydrosol image of underfloor hydronic circuits laid prior to the concrete screed layer with heat pump for heating and reverse cycle cooling.
Underfloor Hydronic Circuits
Image of under-tile electric resistance heating mat
Under-tile electric resistance heating mat

Underfloor Radiant Systems:

Underfloor systems are more radiant than radiator panels. There are two types:

Both systems provide:

  • Luxuriant and even radiant heating
  • Room zoning to reduce power demand

Consider with a new building, renovation or extension. You can retrofit to an existing building but it will be more expensive.

Hydronic underfloor systems

Hydronic underfloor systems provide the most luxuriant form of heating. However, they are expensive to install but very economical to run. This makes underfloor systems highly desirable.

Consider the installation cost as adding to the capital value of your home.

Use your solar power during the day to store thermal energy for release at night.

Hydronic systems use water, which is an excellent medium to store and transfer heat through small insulated water lines with minimal heat loss.

Hydronic underfloor systems are:

      • Designed for large spaces
      • Ideal for high cathedral ceilings or ceiling voids
      • Able to heat and cool with a hydronic heat pump
      • Expensive to install but cheap to run

Underfloor hydronic systems can be installed:

      • In a new concrete slab
      • In a screed layer over top of a concrete slab
      • Over a suspended floor using a thin layer of self-levelling screed in support panels

In-slab underfloor hydronic systems:

      • Take longer to heat up than in-screed systems
      • Are less expensive to install than in-screed systems
      • Use the thermal mass of your concrete slab like a battery storing solar thermal energy for release at night

Undertile heating mats

Undertile heating mats use electric resistance to generate heat. All appliances that use electric resistance are expensive to operate. This includes your electric:

  • Oven
  • Cooktop
  • Kettle
  • Hair dryer
  • Etc

However, if they are used for a short time, their power demand is acceptable.

Electric undertile mats should be used similarly, for a short time. This makes them suited to bathrooms or bedrooms with timers to limit their runtime.

Undertile heating mats are much cheaper to install than hydronic systems, but they are 4 to 5 times more expensive to run.

However, hydronic undertile heating in bathrooms is much more expensive to install. Therefore, it only makes sense if you are installing hydronic systems elsewhere in your house.

Hydronic Radiators & Convectors

Hydronic radiator panels transfer heat by radiation and convection to the room air. 

Hydronic convectors, as the name implies, transfer heat by convection only.

Hydronic radiators and convectors are a good choice with suspended floors and space underneath to run the hydronic pipes.

Key Points:

  • Hydronic radiator panels transfer heat by radiation and natural air convection rising through the hot central fin-coils.
  • Hydronic convectors use an integrated fan to draw air through the fin-coils which increases their effectiveness for transferring heat.
  • Good insulation and air tightness will improve the effectiveness of convected heat transfer by reducing room heat loss.s
Hydrosol image of hydronic radiator panel
Hydronic Radiator Panel
Hydrosol image of Galletti ART-U Hydronic Fan Coil, white, for heating and cooling
Hydronic wall mounted fan coil convector


  • There are a wide variety of radiators available including:
    • Standard ribbed panels
    • Flat linear panels that blend better to your walls
    • Architectural and vertical panels to fit specific décor and tight spaces
    • Towel rails in both Landscape and Portrait orientation

Features of radiator panels:

  • They provide heating only, they cannot cool with a heat pump in reverse-cycle.
  • Despite their name, radiator panels actually transfer more heat via convection than radiation.
  • Heat pump radiator systems can be designed for 60-degree water or up to 75-degrees.


There are a wide variety of convectors available including:

  • Low-wall mounted
  • Under-ceiling mounted
  • Concealed in ceilings, walls or cabinetry

Features of convectors:

  • They provide cooling as well with a heat pump in reverse-cycle.
  • In cooling mode, chilled water is circulated through the fin-coils and condensation is drained to the outside.
  • They use low fan speed in heating mode to avoid overly drying out the air.
  • Higher fan speeds can be used in cooling mode to increase the cooling effectiveness and reduce humidity levels.
Image of Stiebel Eltron electric resistance wall-panel heater
Electric resistance wall-panel heater
Image of Herschel ceiling-mounted infrared panel heaters in a bedroom
Ceiling-mounted infrared panel heaters

Electric Resistance Panels

There two types of electric resistance panels available:

Consider electric-resistance panels if you have a tight budget or looking for temporary solution:

  • Cheaper to install than hydronic systems but more expensive to run
  • Suited to small areas such as bathrooms and bedrooms


  • Electric panels if your house is air-tight and well insulated
  • Infrared panels if your house is leaky and poorly insulated but the heat will stop as soon as they are turned off

Operating Cost Comparison

The operating costs of electric underfloor heating and radiators vary significantly. The following uses the Coefficient of Performance (COP) to compare them:

  • COP is the ratio between the heat output over the power demand (kW).
  • Hydronic heat pump performance varies with outside air temperature, humidity and inside set temperature, so the following is an average guide for the winter climate of Melbourne.
  • Efficiency will be better with good home insulation and air tightness.

Hydronic Systems


  • Hydronic underfloor systems use the lowest water flow temperature, which is easiest for a heat pump.
  • Therefore, they have a typical COP range between 4 to 5, hence the most efficient system.


  • Hydronic fan-coil convector systems are effective with water below 60 degrees.
  • The integrated fan boosts the rate of heat transfer.
  • Therefore, they are the next most efficient system with a typical COP range between 3.5 to 4.5.

Radiator Panels:

It is better to design hydronic radiator panel systems for 60-degree water to improve their COP performance.  However, high-temperature heat pumps are available with 75-degree water if required.

  • Hydronic radiator panels use hotter water than underfloor systems, which requires more work from a heat pump.
  • Therefore, their COP typically ranges between 3 and 4.
  • Hydronic radiator panels less efficient than underfloor and fan-coil convector systems.

Electric Resistance Systems

Electric resistance heaters have a COP of 1 making them much less efficient than hydronic systems.

They are well suited to very cold or alpine climates where the COP of hydronic systems is lower, making the efficiency difference less.

Infrared Radiators:

  • Infrared radiators provide heat from radiation only. There is no convection, hence no heat loss from the air.
  • This makes them ideal for outside applications including decks, restaurants and cafes.
  • They are suited to rooms with short, quick heating requirement such as bathrooms.
  • The heat stops instantly as soon as the radiator is turned off.

Under Tile Heating Mats:

  • Under tile heating mats provide heat via re-radiation from the heated floor surface.
  • Darker colours re-radiate heat better than lighter colours.
  • The floor is heated by conduction from warm electric elements underneath.
  • Electric under tile heating mats cost less to operate than electric resistance radiator panels.

Solar Power

Electric underfloor heating and radiators are most beneficial when paired with solar panels. With sufficient solar panels, the higher cost of running electric resistance systems is not so costly.

However, hydronic systems will give you more available solar power for other appliances and/or an electric vehicle.