ST Saving Hot Water And Energy Info S...
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Mar
27
Sally Blackwell
ST Saving Hot Water And Energy Info Sheet
6
“Sustainability Trust info sheet – How to save hot water and energy”

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ST_Saving Hot Water and Energy Info Sheet.pdf
File Size 0.3 MiB
Date March 27, 2013
Downloads 195
Organisation / Publisher Sustainability Trust
Tags tip sheet, energy conservation, energy efficiency, hot water, energy
Category Checklist and Tipsheets
File Added By Sally Blackwell
File Type pdf
Hub Assured No


  1. This seems quite a complex sheet in terms of the language for the average punter. It also misses a few obvious things (lots of older hot water cylinders don’t have easily accessible thermostats – and most people won’t have the instruction manual, also tempering valves aren’t mentioned and some simple tips on installing insulation around hot water pipes could be useful). In terms of the installing other devices – I’m not familiar with either heat traps or drain water heat recovery, but unless they are phenomenally cheap, surely wrapping the cylinder would be the first best option after sorting out the shower head. Also timers can be a double edged sword – turning off the cylinder overnight might not save any energy, as depending on the efficiency heating it up from cold might use more energy than running it all the time.

    • With less than 100% insulated cylinders, I think there is always a saving from turning the cylinder off in terms of the KWhrs used to heat it up again, versus keeping the same cylinder warm for longer. If you doubt this, try a thought experiment where you keep it on for a week say, using no water, compared with turning it off and heating it up again.

      But where this could make a difference is if a client has time of use rates, or is on ripple control. Time of use rates- you would need to think about when the cylinder is actively heating the water- you could save quite a bit of expense by turning the cylinder on at cheap times. Ripple control- you turn it off, and you may not get hot water again for a while!

  2. There’s a few problems with this info:
    The building code looks to reduce Legionella risk. You should not tell people to turn down cylinder temps below 60°C (around kill temp for Legionella) unless they have considered Legionella issues.
    EnergGuide is north American label here it is Star Ratings Label
    Aerators should be specified in litres per min not gpm (is 1 gpm ie 3.5 litres pm high? )
    Shower flows are key and perhaps should look to tell people how to measure this when to action it. IE if it takes more than 15sec to fill 2 L ice cream container then ok?

    • Yes, I also thought about the Legionella issue. The NZ advice always used to be don’t set the cylinder lower than 60 deg Celcius, in the UK from memory, I think it is 55 deg Celcius.

  3. Thanks Andrew. This is really useful.

    I just want to make one point in general about this process. The idea of getting practitioners to review content in the BPL is so we can develop really good quality info for other practitioners to use that is literally “peer reviewed”.

    At this stage the only people (apart from Beacon) who have put their content up is Sustainability Trust. So I want to congratulate Sustainability Trust for developing these sheets and sharing them with other practitioners. Lets take this feedback and help them turn the sheets into something even better. This is something I’d like to talk about at the workshop coming up and happy to talk to Phil or anyone at ST about this too.

    And thanks again Lois and Andrew,

  4. Continuous flow water heaters may be set to lower temperatures than the standard setting for NZ, which is higher than the Australian default setting. According to feedback from customers, doing that saved them money on water heating in winter.

    With regards to storage hot water cylinders, as I do not have a means of measuring the temperature of the hot water pipe where it comes out of the HWC, I try to at least measure the temperature at the tap. Sometimes I find that the temperature at the tap is above 60 deg, which is an indication that even though the thermostat may appear to be set to 60 deg, the thermostat is not working properly (and there is no tempering valve -like in older houses- or the tempering valve has not been adjusted to take the temperature down to 55deg).
    A note on gas HWCs would be useful, with reference to the issues of insulation and thermostat settings, so that customers don’t think that it is the same advice as for electric HWC.
    The list of Energystar rated dishwashers available at energywise.govt.nz lists boths energy and water use.
    If water pressure is high, a water efficient shower head AND a flow restrictor to the shower or to the whole house may be required as well.
    There are lots of 3-4 bedroom houses with just one or two occupants. The HWC will be of the size needed for a family so the HWC (and the entire house indeed) will be oversized, therefore causing higher energy consumption per occupant.

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