Low energy appliances for your house

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Less Energy Usage

It is difficult to comprehend how much we need to reduce our electrical energy consumption especially as we are surrounded by so many high energy devices that we have come to think as essential (e.g. television, games machines, refrigerator, washing machine).

The average house in Victoria uses between 12 and 15 kWatt.hours of electricity per day.

If the average house has 2.4 occupants, this translates to 5-6.25 kWatt.hours per person per day.

If this is reduced by 15 (a sustainable level of consumption) then the energy consumption per day drops to 0.33-0.42 kWatt.hour per person per day (330-420 Watt.hours). As you will see, this is not a lot of energy, however by using energy efficient appliances and being less materialistic it is an achievable goal.

The reason why we need to reduce energy consumption by 15-fold is because our current Australian Carbon footprint is 15 tonnes/person/year and we need to reduce this to 1 tonne/person/year. This is an easy metric to apply to many things in daily life.

Low Energy Appliances

A list of low electrical energy appliances is presented for comparison and their daily energy requirements. The aim is to achieve a net daily energy consumption of 420 Watts per person.

  • mobile phone - 5 Watt.hours (5 Watts for 1 hour charge)
  • laptop - 92 Watt.hours (65 Watt charger for 85 minutes)
  • headlamp - 5 Watt.hours
  • hair dryer - 25 Watt.hours - (1500 Watts for 1 minute - I used the hairdryer to dry myself after a cold shower)
  • water pump - 5 Watt.hours - (20 Watts, 12V, 800L/hour, 5m lift pumping 50L of water requires 4 minutes) pumps water to header tank or directly to garden. Very useful for the garden [1]
  • small camping refrigerator - 288 Watt.hours - (12 Watts, 12V, 1 Amp, 24 hours, Engel 40L Fridge Freezer)

420 Watt.hours in total

Intermittent Low Energy Appliances

  • Some appliances are low energy and are only used intermittently or can be turned off when not in use.
    • Desk lamp - 6 Wh (3 Watts x 2 hours)
    • Home router - 9 Wh (3 Watts x 3 hours)
    • NBN router - 9 Wh (3 Watts x 3 hours)
    • Electric bike - 200 Wh (100 Watt charger for 2 hours) - charging battery every 4 days
    • Heat Recovery System (Stiebel Eltron VLR 70 S) - 184 Wh (2 x units, 23 Watts x 8 hours) - during very hot or cold periods

Optional and Intermittent Electrical Appliances

  • battery chargers - to charge rechargeable batteries
  • multimeter - to check the charge state of batteries
  • small rechargeable devices - electric tooth brush, shaver, portable vacuum cleaner, camera, portable games console
  • electric fan - for personal cooling
  • rechargeable power tools - for construction projects
  • small water heater - for hot drinks and for showering (you can also use gas to heat water and a thermos to keep it hot)
  • inverter - you can connect an inverter to a battery to convert DC to AC. This allows you to run some appliances that still need to run on 240V AC.

High Energy Appliances that cannot or should not be used

There are many appliances that we use today that will use up too much electricity to be justified in a lower energy and low resource future.

  • refrigerator - uses large amounts of electricity and is generally poorly insulated. Smaller options available (e.g. Engel)
  • air conditioners - use large amounts of energy (2 kW+).
  • evaporative cooler - uses 200 Watts of power and 12L of water per hour.
  • hot water heat pumps - use 800 Watts for 3-4 hours to heat water
  • electric oven - very high energy consumption. Use gas, a solar oven, or a limited amount of wood.
  • electric cook tops - very high energy consumption. Use gas or a solar oven.
  • vacuum cleaner - polished floors can be cleaned using broom and mop
  • television and sound systems - program and movies viewer using laptops and tablets
  • printer - replace with electronic documents or print elsewhere
  • kitchen appliances - there is often a manual substitute
  • clothes iron - may only be needed on rare occasions. There may be low energy 12V substitutes.
  • home alarm system - may not be required if you have good neighbours
  • games consoles - are considered a luxury
  • washing machine - energy efficient models exist, but can hand wash and wash less
  • clothes dryer - high energy. Use a washing line.
  • dish washer - high energy for heating water. Highly alkaline (high pH) detergent that has a high salt content. Cannot be used in the garden. Wash by hand using biodegradable detergents.
  • electric car - too energy and resource intensive
  • electric bike - may have some uses, hwoever a conventional bike will have a longer life and be less costly to run
  • electric scooter - will have a relatively short active life. Not a good investment.
  • rice cooker - use gas for cooking rather than electricity. Rice production has a high carbon footprint.
  • electric kettle - very high energy use. Up to 2000 Watts.
  • exhaust fans - not really necessary. Have short 1 minute showers and use tepid water. Open windows in bathrooms for ventilation. Use decentralised heat recovery ventilation systems as an alternative.

Emissions associated with Mobile Phones and the Internet

There are significant CO2e emissions associated with the use of technology.

  • A typical laptop will contribute 250 kg CO2e of embodied emissions.
  • A typical business user may create 135 kg CO2e from sending emails every year [2].
  • An iPhone with 120 GB storage capacity has 72 kg CO2e of embodied emissions [3].
  • Mobile data consumption of 45 GB each month will contribute 600 kg of CO2e per year due to the energy demand of data centres. Optus offer a yearly recharge for $300 (365 days, 300 GB mobile data). The carbon footprint would be expected to be 330 kg CO2e.

Solar Off-grid PV System with Battery Storage

A solar off-grid PV system with Battery storage was constructed to investigate low energy usage systems.

The components of the system are summarised:

  • LiFePO4 Battery Pack iTECH120 - 120 Amp.hour storage - $900
  • Victron SmartSolar 100 VOC, 20 Amp MPPT solar panel charge controller - $250
  • 1000 Watt 12V pure sinewave inverter (RedArc) - $1,100
  • Victron Energy Smart Battery Monitor and shunt - $300
  • Solar panel 65 Watt - could be upgraded to 200 Watt panel

This system is able to deliver 470 Watt.hours per day (120 Ah x 13V x 30% discharge) which will discharge the Battery Pack to 70% capacity. Limiting the amount of battery discharge will help to preserve battery life (up to 20 years - 8000+ discharge cycles).

Carbon Emissions associated with Battery Manufacture

  • According to the Union of Concerned Scientists, lithium-ion batteries produce about 68kg CO2e per kWh of battery capacity during manufacture [4].
  • The iTech120X 120Ah LiFePO4 Battery has a stated capacity of 120 Ah (12-13.5V) which equates to 1.44 kWh (120 Ah x 12 V).
  • The CO2e emissions are therefore 68 CO2e per kWh x 1.44 kWh = 98 kg, for a 10kg battery.
  • Even though emissions appear modest, there are still significant environmental impacts associated with mining, manufacture, end of life disposal and the risk of fire.

Battery Lifecycles

iTechWorld publish the battery life cycle for the ITech120X 120Ah LiFePO4 Battery. The greater the discharge of the battery, the shorter the battery life. In a resource constrained world we will need to maximise the useful life of all things.

  • 80% discharge - 2000+ life cycles (2000 / 365 = 5.4 years) - assuming that the battery is discharge and then recharged daily.
  • 50% discharge - 5000+ life cycles (5000 / 365 = 13.7 years)
  • 30% discharge - 8000+ life cycles (8000 / 365 = 21.9 years)

By comparison, a solar PV panel will still produce 80% of nameplate wattage even after 25 years (standard performance warranty for industry).

Inverter Technology

  • In our homes many of our appliances run on 240V AC mains power.
  • Solar PV systems produce DC electricity. The DC voltage is typically 12V, 24V or 48V.
  • In some cases the DC may be used directly if it is at the correct voltage.
  • However some appliances still need the DC to be converted to AV. To make this conversion an Inverter is used.
  • An Inverter will convert an input DC voltage into 240V AC so that it can be used by household appliances.
  • Inverters have a Wattage rating. The inverter will shutdown if the Wattage rating is exceeded (e.g. 1000 Watt rating).
  • Good quality inverter are expensive (e.g. $1000 for RedArc inverter) and will have an expected life of 8-10 years.
  • Because Inverters produce 240V AC appropriate safety precautions need to be taken to guard against electrocution.
  • Inverters also add to losses of energy within the system. The RedArc inverter has a loss of approximately 20Watts during operation (13.5V, 1.6A draw current).

12 Volt DC Appliances

  • Batteries used in solar PV systems store electrical energy from the sun. Before this stored DC energy can be used it needs to be at the correct voltage for the appliance being used.
  • Typically, most DC appliances need to be supplied with either 24V, 12V or 5V DC. Many camping and off-grid stores sell DC appliances rather than conventional AC appliances.
  • The DC voltage of a Lithium Iron Phosphate battery (LiFePO4) battery will vary between 12.5V and 14.5V depending on the charge state of the battery.
  • To convert a variable battery voltage to a stable 12V DC output supply a Voltage Stabiliser is used RedArc Voltage Stabiliser.

5 Volt DC Appliances

  • A variable battery voltage can be converted to higher or lower voltages using DC-DC Buck Converter.
  • You can power small computers (e.g. Raspberry Pi) and charge other small devices using these small DC-DC 5V converters.

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