Is My Hot Water System Causing High Electricity Bills?

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Hot water systems are often blamed for high electricity bills.  As passionate plumbers in Gymea, we want to defend the hot water systems in Cronulla and present other reasons why your power bill is high.  This data is from energy audits of homes and businesses around NSW:

  • Ducted air conditioning
  • Electric water heaters
  • Other electric heaters
  • Water pumps
  • Refrigeration
  • Lighting
  • Solar panels (with issues)

How can you reduce energy use?

Air Conditioning

Ducted air conditioning tops the list for households and workplaces, representing approximately 50% of an electricity bill with their high input power ratings.  A domestic system consumes about 5kW so e.g. over 5 hours/day, 180 days/year, at $0.25 per kWh = $1,125 per annum.  Every 1˚C adjustment on the thermostat (heating or cooling) equals 5-10% savings.

Insulate your building, use shading and fix drafts to use less air conditioning. 

Water Heaters

Hot water systems can represent 30% of a household’s energy bill, whether it be a tank or an instantaneous system.

To reduce this, do the following:

  • Immediately attend to dripping taps or tank leaks
  • Install efficient fixtures and showerheads
  • Stop taking very long showers
  • Turn off all instant hot water boilers after hours
  • Reduce the set-point temperature
  • Insulate pipework/tank.
  • Turn off office hot water devices after hours.

Other Heaters

Plug-in electric heaters consume vast amounts of power.  A single 2 kW electric heater, running 8 hours/day will add $360 to one quarterly power bill.

Underfloor electric and heated towel rails deliver high bills if running all day.  Some in-slab heating can be left on without you noticing!

Clothes dryers can use 5kWh of electricity per load.

Ovens in a commercial kitchen can use up to 40kW each and if frequently used at home the impact on the electricity bill will be substantial.

Action to take:

  • Use timers on underfloor heating / heated towel rails. 
  • If you use a clothes dryer frequently invest in a ‘heat pump’ dryer.

Water Pumps

Households with pools have the highest electricity bills, mainly due to the pool filter pump.  Over-spec filter pumps are usually installed with the pump running for a “recommended” 8 hours a day, which is mostly not necessary.

Irrigation pumps also add hugely to energy bills.  Note: the pump’s motor speed is important in relation to energy bills.  

We advise that you check if you can:

  • Reduce the pool pumps operating time
  • Use a smaller pump for a longer time for irrigation.


Refrigerators are actually energy efficient.  It’s the quantity of them that puts a dent in an energy bill.  Big electricity bills often have two or more refrigerators contributing to the bill. 

For cafes, restaurants and clubs, refrigeration can be their single biggest energy user.

Actions to take:

  • Consolidate the number of devices in use.  
  • Anything that is not perishable should go into a fridge that is on a timer.
  • At home use a set-point of 4˚C in the fridge and -15˚C for the freezer.
  • Maximise cool room insulation, maintain the door seal and use a PVC door curtain.


Lighting has the most energy-saving opportunities available. 

Actions to take:

  • Upgrade all lights and fitting to energy-efficient LED.
  • Install LED lights with motion sensors.
  • Don’t over-spec lighting.  Light levels can be lower in corridors and storage areas.

Solar Panels

If you don’t understand how solar panels work you could cause high electricity bills.  These could be the cause:

  • Lack of knowledge
  • Maintenance issue.
  • A billing or metering problem.

Some people assume solar power means that the use of their ducted aircon has no impact on the energy bill.  This is solely dependent on the weather, time of year, time of day, size of air conditioner, and size of the PV array.  Additionally, a maintenance issue might be missed due to your lack of knowledge.

Action to take:

  • Install a solar energy monitor.
  • Check that a ‘feed-in tariff’ is appearing on your power bills.
  • Check your inverter once every few months.

Contact us today if you need assistance from a plumber in Gymea, Kirrawee, Sutherland Shire or Sydney with adjusting your water heating system to a more energy-efficient system.





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