Electric heating

Most electric heaters are relatively cheap to buy, but they are difficult and expensive way to heat a home. Living rooms heated by electric heaters tend to be colder than where other types of heaters (except for open fires) are used, according to a BRANZ study. [1]

For your home's primary heating system, it is worth investing in a more efficient and effective option, such as a modern wood or wood-pellet burners, an ENERGY STAR® qualified heat pump or high star-rated flued gas heaters.

When are electric heaters an option?

Electric heaters can be suitable for:

  • for smaller rooms that only get used occasionally, for short periods of time
  • using instead of portable LPG heaters or open fires - electric heaters much safer and cheaper to run

Are some electric heaters more efficient than others?

With the exception of heat pumps, all electric heaters are equally efficient. They convert all the electricity they consume into useful heat - no more and no less - so don't believe claims that any one type is more efficient than the other.

Some electric heaters are being promoted as "eco" or cheap to run. Often they just have a very low heating capacity which is insufficient to heat a room to comfortable and healthy temperatures. So while they may cost less to run, they also produce very little heat.

How much do they cost to run?

The running cost of an electric heater is determined by:

  • its capacity, expressed in Watts (W) or kilowatts (kW) (1000 W = 1 kW). Note that the capacity you need is determined by the heating needs of the room. A heater with too little capacity will not be able to heat the room up to comfortable and healthy temperatures.
  • your electricity tariff (typically around 24 cents per kWh[2] for uncontrolled electricity supply, usually less for night-rate supply to night-store heaters)
  • how long you use them for. on (note that thermostatically controlled heaters will turn themselves on and off automatically to maintain the set temperature, i.e. the time they are actually consuming electricity will be less than the time you have switched them on, provided they have sufficient capacity and that the thermostat is actually working properly).

To work out how much an electric heater costs to run for an hour in cents, take the capacity of the heater in kilowatts (1 kW = 1,000 Watts) and multiply by 24[2] (or your actual tariff). So for example, a 2 kW (= 2000 W) heater costs around 48 cents per hour to run.

Choosing an electric heater

What size heater do you need?

The size of heater that you need is determined by a number of factors. Use the free Consumer heater sizing calculator to get an idea how much heat a room needs to keep it at healthy temperatures.

The heating capacity of electric plug-in heaters is typically no more than 2.4 kW. This means in larger and/or poorly insulated rooms you may need to run more than one heater to reach comfortable and healthy temperatures. Only use one heater per power outlet as one heater will fully load an outlet.

Different types of heaters for different heating needs

Different kinds of electric heaters - such as radiant, fan, convection and night store heaters - distribute their heat differently to suit different circumstances.

Choosing the right type of heater for the application is important so you actually get to feel the heat you're paying for as much as possible.

Radiant heaters

The familiar bar heater with glowing elements and a reflector is a radiant heater. These mainly heat objects and people rather than the air in a room. They are commonly available as either free-standing, wall or high-wall mounted models.
They can be useful:

  • in large rooms where you only need the heat in one area, or
  • where you want to feel instant heat without waiting until the air in the room has warmed up, e.g. in large bathrooms (only use high wall mounted models here), while standing at the kitchen sink or for that quick early morning breakfast in a cold house.

Radiant heaters can be a fire risk if in close proximity to flammable materials and are dangerous to children. High-wall mounted models can be installed out of reach from children and away from flammable materials.

There are more modern versions of the radiant heater, often called a panel, marble or stonestore heater, where the elements are behind, or inside a panel or other mass made of metal, brick, stone or something more expensive like marble. These heaters give a more even, lower temperature heat, but still cost the same to run for a set amount of heat. They are not any more efficient than any other type of electric heater, don't believe any marketing that says they are.

Fan heaters

Fan heaters, sometimes also called ceramic heaters, can be noisy but are good for distributing heated air around the room rather than letting it form a layer of hot air below the ceiling.

They are good for:

  • boosting a convection heater while heating up a room by providing additional heating capacity and helping with better distributing heated air, so the room feels warm quicker.
  • quick warmth in smaller rooms which require heating for very short periods of time, for instance in the kitchen or bathroom in the morning
  • keeping children safe - high-wall mounted models can be installed out of reach from children for their and your home's safety,.

Convection heaters

A convection heater mainly heats the air rather than surfaces. These include column heaters (oil and 'oil-free') and convection heaters with a heating element inside a casing which has grilles at the top and bottom to allow air to flow through.

These are a good choice for medium-sized rooms that require heating for longer periods of time, such as living rooms and bedrooms. They steadily warm the air by convection - the hot air rising and then slowly circulating around the room - and provide background warmth.

Some have a built-in fan to better mix the air while warming up a room to achieve a more even room temperature quicker.

Their surface temperatures are relatively low, which makes them safer than radiant heaters.

Note that they can easily be tipped over by children unless fixed in place - the weight and sharp fins of oil column heaters can be particularly dangerous to your little ones.

Night store heaters

Night store heaters use mass like bricks to store heat from cheaper off-peak electricity at night and slowly release it during the day. They can be more economical than common electric heaters for houses that are occupied during the day, and where a cheaper night rate tariff for electricity is available.
However, if your house is empty during the day, these are not a good heating option for you as a lot of the heat will be released when it is not needed.

Electric underfloor heating

Electric underfloor heating is similar to an electric blanket that goes on top of your floor. It goes between any floor covering like carpet or thin timber flooring and the floor itself.

Any covering that goes on top of the electric underfloor heating makes it harder for the heat to get into the room.

It is very important that the floor is well insulated underneath, otherwise a lot of the heat you pay for will be lost downwards.

Although electric underfloor heating can heat large areas well, it can be expensive to run.

Features to look for

Thermostats help maintaining an even temperature and conserving electricity. Some electric heaters have a temperature dial, but most don't and require a lot more trial and error until the desired thermostat setting is found.

The room temperature needs to be quite even to feel comfortable which requires a reasonably accurate heater thermostat. Most of us won't feel very comfortable if the heater allows the temperature in the room to fluctuate by several degrees Celsius. Unfortunately the accuracy of built-in heater thermostats varies greatly as often the heater itself interferes with the temperature sensor of the thermostat. The temperature sensor should be located as far away as possible from the heated parts of the heater, e.g. at the bottom of the heater where the unheated room air is drawn in. Also check whether the heater specifications provide any claimed thermostat accuracy.

Alternatively you can get an electrician to install a separate, hard-wired room thermostat to control the heater. These are usually wall-mounted and, if installed correctly, will better sense the actual room temperature.

Timers allow you to turn a heater on to warm up the kitchen half an hour before you get up, or to turn a heater off after you have gone to bed.

Fans help a room warm up faster by distributing the air more evenly rather than letting heat build-up near the ceiling.

Thermal cutout: Some heaters have a built-in thermal cutout which turn the heater off if it overheats - this is an important safety feature to look for.

Tilt switch: Some portable heaters have a built-in tilt switch which turns the heater off if the heater overturns - another important safety feature to look for.

Use your electric heaters wisely

  • Only heat the areas you're using, and only while you're using them.
  • Keep the heat in by shutting doors and curtains.
  • Set the thermostat for healthy indoor temperatures. World Health Organisation guidelines recommend at least 18˚C in any rooms you're using (or at least 20˚C if you have vulnerable people in the home, like children, the elderly or the ill), and at least 16˚C in bedrooms overnight.

More information

You can find test reports on electric heater models at Consumer Online.

Notes:

[1] BRANZ Ltd: Report on the Year Ten Analysis for the Household Energy End-Use Project (HEEP), 2006

[2] Ministry of Economic Development, 2008, Schedule of Domestic Electricity Prices: Updated to 15 November 2008, 2008, (online).

From the Resource Centre

Related documents and additional information: