Craig on electric hot water cylinders
Published 23 May 2015
The majority of hot water systems in New Zealand are electric.
Heating water makes up 30-40% of a total electricity bill per month through summer and winter so it’s very important to make sure your system is set up correctly and working as efficiently as possible to avoid wasting money and energy.
Grading: If your cylinder is 2004 or newer look for an A-grade label or MEPS compliment, this means your cylinder meets a minimum energy performance standard and is already pre-insulated to keep the warmth in. If your cylinder does not have one of these labels then consider fitting a cylinder wrap to decrease heat losses. If your cylinder is installed in an attic or underfloor cavity it’s often a good idea to wrap them anyway as these are colder environments.
Thermostat: Hot water cylinders need to be heated to at least 60 degrees Celsius or 140 degrees Fahrenheit once a day to stop bacteria building up on the bottom of the cylinder. We recommend setting your cylinder at a minimum of 60 degrees Celsius. If your cylinder is set hotter than this it could be costing more and will have higher heat losses (the hotter the cylinder the more heat it loses through its surface). Most cylinders can have their thermostats adjusted by removing the small panel on the front. This should always be done with the power switched off and, ideally, by a qualified plumber or electrician. Some cylinders will also have ‘tempering valves’ to cool the hot water down as it exits the cylinder (to avoid scolding at the tap). These can be adjusted after changing the temperature at the cylinder to the correct 60 degrees.
Insulation: Wrapping a cylinder will typically save $50 a year so cylinder wraps will take between 1-2 years to pay themselves off. The biggest drawback is access to the cylinder as they need to be fully wrapped around the cylinder. If a cylinder is placed hard up against a wall then wrapping is difficult or impossible. Making sure your hot water outlet pipe is insulated is very important and cost-effective. The first metre of pipe is the most important and putting pipe lagging around it will typically save $10 a month - pipe lagging costs around $10 and is an extremely simple yet effective way to save on energy costs.
Pressure: Cylinders will either be low/mixed pressure or mains pressure and should be labelled but, if not, judgement can be made based on shower pressure. A low flow cylinder will typically result in an efficient shower flow of around nine litres per minute whereas a mains pressure system will have a flow rate of anywhere between 12 and 24 litres per minute (sometimes more!). A solution is fitting a low flow showerhead which will use only nine litres per minute – this will save money and water. In fact, with a water pressure of 24 litres per minute, a low flow showerhead will save around $200 per person per year based on a 5-minute daily shower. These showerheads are available through the WCC home energy saver program at a subsidised rate. Book a free energy saver assessment here.
Going Away? If you’re going away on holiday consider turning off your hot water cylinder and remember to switch it back on when you get back.