Sustainable Living Ideas NZ

Heating Cost Comparison

Deciding on which heating option to use to heat your home is an important one. There are a wide range of heating options available, and choosing the most suitable heating option depends on a number of factors.

According to the World Health Organisation, the minimum temperature for living areas should be between 18 and 21 degrees celsius, and 16 degrees celsius for bedrooms.

In addition, it is advised to keep indoor temperature at least 7 degrees celsius warmer than the outside temperature on cold days to avoid condensation forming.

Heating options

Below is a list of the advantages, disadvantages and indicative costs of the most common home heating options available.

Heat pumps

Advantages

Heat pumps work by transferring free heat from outside the home into the room. They are effectively an air conditioner unit in reverse. As such, they can also can be used in reverse mode as an air conditioner during warm summer days. They are 200% to 500% efficient depending on the make and model. look for the Energy star rating or compare kW used vs kW produced.
They have low running costs.
They are a clean heating source.
They filter the air, so heat pumps are considered suitable for people with asthma and airborne allergies.

Disadvantages

Heat pumps are expensive to buy and install. It can take a number of years to recoup the initial costs.
Heat pump efficiency drops when outside temperatures drop below 2 degrees Celsius. Although some newer models have improved performance at lower outside temperatures.
A standard Hi Wall heat pump is sometimes not well suited for older villa style homes with high ceilings.
There can be a tendency to overuse heat pumps, leaving them on when it's not necessary, thereby negating the energy savings.

Cost

Purchase and installation cost - $2000 - $5000 per unit (room),depending on size
Maintenance - Filters need to be changed occasionally
Running cost (cents / kWhr) - 6.5 - 8.9c
Output - 3 - 7 kW
Cost per hour - 19.5 - 62.3c (depends on kW rating and power setting used)
Energy efficiency - 200 - 500% (depending on make and model)

Electric heaters

Advantages

Electric heaters are 100% efficient, meaning all the energy consumed is converted into heat
They are a clean form of home heating.
They provide heat immediately.
If you choose an electric heater with a thermostat control, the temperature can be controlled accurately, and the heater can be used more efficiently.
Electric heaters are cheap to buy and usually require no installation costs.
Many electric heaters come with a timer (or you can plug in a separate timer switch), which means rooms can be set to be pre-heated.

Disadvantages

Electric heaters can be more expensive to run than non-electric options, depending on the fluctuating price of electricity
Fan heaters are less energy efficient since some of the electricity consumed is used to power the fan.

Cost

Purchase and installation cost - $50 - $500
Maintenance - None
Running cost (cents / kWhr) - 17.5c
Output - 1 - 3 kW
Cost per hour - 17.5 - 52.5c (depends on kW rating and power setting used)
Energy efficiency - 100% (less for fan heaters)

Night store heaters

Advantages

Night store heaters work with Night and Day power plans to use electricity at night on the cheaper night rate to generate and store heat. The stored heat is then released during the day.
They are suitable for homes where the occupants are home during the day
They a clean form of heating
Heat is created using the cheaper night time energy prices

Disadvantages

They are only considered 80% efficient because some of the stored heat is lost before it is released.
There is a higher purchase and installation cost than regular plug-in electric heaters
They are not so suitable for people who are out during the day and home at night (most households) since there is little heat left for the evenings.

Cost

Purchase and installation cost - $1050 - 1150
Maintenance - None
Running cost (cents / kWhr) - 8.4c
Output - 1.7 - 6kW
Cost per hour - 14.28 - 50.4c (depends on kW rating)
Energy efficiency - 80%

Log Burners

Advantages

Log burners are suitable for heating large areas such as the living room, or open plan homes.
They are cheap to run
If you have access to a free fire wood supply, they can be very cost effective.
A wetback can be fitted to also heat your water
They are attractive and often provide a feature for the main living area.

Disadvantages

They are not particularly clean, and produce smoke which pollutes the air.
It is more difficult to control the amount of heat being output from a log burner. This means you may use more energy than you actually need.
Log burners do not produce instant heat. It takes some the before the room begins to heat up.
There is extra work and space required, chopping, stacking and storing firewood.

Cost

Purchase and installation cost - $1500 - 6000
Maintenance - Flue should be inspected every year. Average inspection cost $40 - 50
Running cost (cents / kWhr) - 5 - 8c
Output - 5 - 24kW
Cost per hour - 25c - $1.92 (depends on kW rating of the logburner)
Energy efficiency - 55 - 80%

Pellet Fires

Advantages

They burn cleaner than logburners, resulting in less polluted air
Pellet fires are more energy efficient than logburners
They are suitable for heating a large area effectively
You have a greater control of the temperature
They provide a feature for the room.
There is less preparation of fuel and cleaning required
A wetback can be fitted to some models to also heat the water in the home.

Disadvantages

They require storing of large pellet bags.
They still require electricity to run.
You need to clear the ashes regularly.
They can be noisy.

Cost

Purchase and installation cost - $2500 - 5000
Maintenance - Flue should be inspected every year. Average inspection cost $40 - 50
Running cost (cents / kWhr) - 7 - 9c
Output - 10kW
Cost per hour - 70 - 90c
Energy efficiency - 75 - 92%

Flued Gas

Advantages

They are clean burning.
The level of heat can be controlled easily.
Flued gas provides a high heat output and the heat is instant
Flued gas heaters don’t create dampness and health problems like portable gas heaters do.

Disadvantages

There is the added cost of buying or renting the gas bottle rental.
They are more expensive to install than electric heaters.

Cost

Purchase and installation cost - $2500 - 3000
Maintenance - Occasional inspection required, once every 3 years on average. Average inspection cost $100
Running cost (cents / kWhr) - 14 - 21c
Output - 3 - 8kW
Cost per hour - 42 - 168c (depends on output and gas costs)
Energy efficiency - 60 - 80%

Unflued Portable Gas Heaters

Unflued portable gas heaters are not recommend for the following reasons. In fact they are banned in some countries:

They produce a lot of heat from an open flame which is a fire risk.
They rely on combustion which reduces oxygen levels in the air and increases carbon dioxide levels.
As they get older, they can deteriorate, becoming less efficient and releasing carbon monoxide into the air, which is toxic and dangerous.
Using portable gas heaters in areas where people are sleeping is very dangerous. People who are asleep will not be able to respond if the carbon levels in the room reach a dangerous level, which could lead to asphyxiation.
They release approximately 1 litre of moisture into the air, per hour.

Lighting choices for conserving energy

Artificial lighting is a necessity in a modern home, unless you're happy to live by candlelight. Lighting requirements also increase during the winter as the days get shorter.

On average, lighting accounts for 10% of a household's energy consumption. You can improve on this by taking one or more of the following steps:

Design your home to take maximum advantage of natural light when it is available.
- Install roof lights or skylights in areas where it's not possible to include a window, such as internal hallways and corridors.
- Include large windows on north facing aspects (for Southern hemisphere) to take advantage of daylight hours. Keep in mind that double glazing should be used where possible to minimise heat loss through the window system.
Using lighter colours for interior surfaces reduces the need to use artificial lighting

Think about the design and placement of lighting and switches so you only turn on the lights you need, and it's easy to switch off lights that aren't required. Also ensure each lighting installation has it's own switch so you only switch on the lights you actually need.

Install energy saving light bulbs. These use approximately 1/7th what a standard light bulb does and they also last longer.

Consider installing delay timers, movement sensors and dimmers to reduce the amount of energy used from lighting. Delay timers can be set to switch off after a certain amount of time. These are perfect for rooms that are only used for a short period of time such as store rooms and toilets, however they can cause a safety issue if the timer is set too short. Movement sensors are great for entrance ways and can also provide a security element.

How to Increase Energy Efficiency

Energy efficiency is at the core of sustainable building practices. The ideal goal in many people's eyes is to achieve a house that can generate all the energy it needs for it's inhabitants. This is achieved by taking energy efficiency measures including a combination of generating energy through renewable means such as wind and solar, and also by reducing the amount of energy being used.

Whilst the idea of a home that is not dependent on the national grid for power sounds great, for most homes it's not realistic or cost effective. However a more realistic goal is to increase energy efficiency in the home and thereby reduce the amount of energy being consumed, and to supplement the national energy supply with solar panels, solar hot water and in some cases wind turbines.

So what steps can we take to reduce our energy consumption?

There are numerous ways to reduce energy use without having to make any changes or renovations to the house. These include using energy saving light bulbs, unplugging appliances with standby functions, taking shorter showers and turning off lights and other electrical appliances when not in use.

However, we need to look at the largest users of electricity in the home. These are space heating and hot water heating.

Hot water cylinders should be insulated, and the first 3 meters of piping should be lagged.

Where possible, the hot water cylinder should be positioned as close as possible to the kitchen. This is where short bursts of hot water are most often used.

Where possible, install insulation in the ceiling and under the floor. For existing homes, retro fitting insulation into the walls is often difficult and costly. However the most heat is lost through the roof, so you should focus your attention there.

During the design stage, plan your house to maximise window size on the northern aspects (for southern hemisphere) and minimise window size on southerly aspects.

Install double glazed windows with thermally broken frames to reduce heat loss through the window system. However you should still allow for controllable passive ventilation to remove moisture from the air. Remember it's easier and cheaper to heat fresh dry air. The balance between heating, ventilation and insulation is important, but all three need to be working together to ensure a healthy indoor environment.

Passive Background Ventilation

How does Background Ventilation Work?

Background ventilation uses the principle of pressure equalisation, where wind flow around a building creates a higher air pressure on the windy side and lower air pressure on the sheltered side. Due to this difference in air pressure, fresh air is pulled into the building on the windward side and stale air is expelled to the sheltered side. This ventilation requires no power source or fans.

How to control condensation

Condensation occurs when water vapour in the air is cooled to it’s dew point. This commonly occurs when the water vapour in the air comes into contact with a cold surface such as glass windows.

Excessive condensation can cause mildew to appear on curtains and furnishings and walls causing costly damage over time.

Condensation can be minimised or eliminated by adhering to the following principles:

Reduce the amount of moisture being generated in the home.

Ventilate the building to remove moisture laden air to the outside and replace with drier fresh air.

Increase the internal temperature during the winter months to a level 5-7 degrees (celsius) higher than outside. It is far easier and cost effective to heat dry air than damp air. Therefore, while it may seem counter-productive to open vents during cold weather, the benefits of proper ventilation often outweighs the mimnimal extra heating required.

Insulate exterior walls and ceiling to assist in reducing heat loss.