Collage of radiant heating systems
Radiant heating systems

Use your solar power for electric underfloor heating and radiators. This BLOG explores your options including:

  • Electric resistance systems:
    • Radiators and convectors
    • Infrared radiators
  • Hydronic heating systems:
    • Underfloor systems
    • Radiator panels

For heating and cooling systems, air-to-air (air conditioners) or air-to-water heat pumps using fan-coil convectors are best.

Costs:

  • 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 comfort:

  • 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
  • Lower your panel temperatures to:
    • Reduce running costs
    • Make it easier for a hydronic heat pump, hence lower running costs
  • Electric systems are safe:
    • There are no pilot flames
    • There are no gas leaks to worry about

Mix and match:

Consider a mix of hydronic radiant systems with electric element systems to lower installation costs with reasonable running costs.

Electric undertile mats are cost effective for bathrooms whereas heat pump systems are better for large living spaces. 

For a two storey house, consider hydronic radiant systems at least for the ground floor. The rising heat will reduce the heating required upstairs.

Therefore, if your bedrooms are located on the first floor, electric radiator panels could be considered for each room.

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 provide a more luxuriant radiant warmth. There are two types:

  • Hydronic systems
  • Electric resistance mats

Both systems provide:

  • Even heating across the floor surface
  • 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 are a very efficient form of heating. They can be used with your solar power during the day to store thermal energy in your floor for re-radiation in the evening.

However, they are more expensive to install. So consider the installation cost as adding capital value to your home.

Hydronic underfloor systems are:

      • Designed for large spaces
      • Ideal for high cathedral ceilings or ceiling voids
      • Able to heat and cool with some hydronic heat pump systems

Underfloor hydronic systems can be installed:

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

In-slab compared to in-screed systems:

      • In-slab takes longer to heat up
      • In-slab systems are less expensive to install than in-screed systems
      • In-slab systems can store more thermal energy during the day
      • In-screed systems can be used as your finished, polished floor

Undertile heating mats

Undertile heating mats use electric resistance to generate heat. All appliances that use electric resistance are expensive to operate, including:

  • 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

Hydronic radiator panels transfer heat by both radiation and convection. Warm air rises through the middle of the radiator panels to heat your rooms.

Hydronic radiators are a good choice with suspended floors. The hydronic pipes can be run under your sub floor.

Good insulation and air tightness will improve effectiveness by reducing room heat loss.

Hydrosol image of hydronic radiator panel
Hydronic Radiator Panel

Types

  • 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

Features of radiator panels:

  • They provide heating only, cannot cool
  • Radiator panels provide heat via radiation and convection
  • Hydronic high-temperature heat pumps can be used with radiator panels. They can heat water up to 75-degrees.
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 Heaters

Electric resistance heaters are cheaper to install than heat pump systems but more expensive to run.

They are better suited to small areas such as bathrooms and bedrooms

There three types of electric resistance heaters:

  • Electric wall radiators
  • Electric wall convectors
  • Undertile mats

Also, you could consider infrared panels for radiant heating.

Consider electric-resistance heaters if you have a tight budget. They work better if your house is air-tight and well insulated because they heat the room air.

Consider infrared panels if your house is leaky and poorly insulated because they heat only the objects in your room, not the air. Note that the heat will stop as soon as they are turned off.

More information:

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

Underfloor:

  • 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.

Radiator Panels:

It is better to design hydronic radiator panel systems for 60-degree water to improve their COP performance.  However, high-temperature systems are available 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 systems are less efficient than underfloor 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 also have a COP of 1. However, they only need to operate when people are in a room because they heat instantly. Therefore, they can be turned off when people leave the room.
  • This makes them ideal also for outdoor applications such as alfresco areas.
  • They are suited to rooms with short, quick heating requirement such as bathrooms.

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.

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