Lower hot water bills on the way

Home owners are set to save money through strengthened energy efficiency rules for new hot water systems, says Shane Jones.

From December 2008, all new domestic hot water systems in either new or refurbished homes will need to meet more stringent energy efficiency standards.

The new Building Code requirements are expected to save the average homeowner at least 13 percent in water heating costs, with minimal extra investment needed up front.

Most homeowners with average-sized homes will be able to comply by installing water efficient showerheads. These can halve the amount of hot water used, with no noticeable loss in the quality of the shower.

Other options for complying include modern technologies such as solar water heating; instantaneous gas hot water and shower drain heat recovery units (a device that recovers heat from hot water going down the drain).

No single option will be compulsory. Homeowners will be able to choose from a variety of options, ranging from the basic (bringing good savings) to the advanced (bringing excellent savings). With each option chosen, the savings add up, and the payback periods on the extra initial investment needed are short.

Building and Construction Minister Shane Jones said, “Even with basic measures, people stand to save hundreds of dollars a year in water heating costs. Reducing carbon emissions from water heating, which consumes about a third of our domestic energy use, will also be good for the environment.”

To make compliance easier, the Department of Building and Housing will publish a simple computer programme that homeowners and designers will be able to use to work out if their system complies with the new requirements. The programme will be available on the internet.

As part of the same package, other changes to the Building Code will also require new heating, ventilation and air-conditioning systems in commercial buildings to be energy efficient, potentially saving commercial building owners and tenants thousands in unnecessary energy bills.

Notes for editors

The fictitious case-studies below are aimed at illustrating how simple energy-saving measures can reduce power bills (and water bills where water is metered).

Case study 1:

John and Mary are rebuilding a 100 m2 cottage in Wellington. This involves changing the existing low-pressure water system to high pressure. Without energy efficiency measures, this would change the shower flow rate from 3 L/min to 15 L/minute, resulting in a huge increase in the cost of hot water – by about $600 per year. However, with the new Building Code requirement to use a basic energy saving measure (a water efficient showerhead delivering 7.5 L/min), their total hot water bill would be $530, saving $350 per year. The cost of the water efficient showerhead is $120, giving a payback period of four months.

Case study 2:

Hone and Tracey are building a new 200 m2 home in Whangarei, with four bedrooms. The builder suggests a gas storage water heater, but it turns out this would be an inefficient system, with an estimated annual running cost of $880. The new Building Code requirements mean that, in their circumstances, such a system does not meet the benchmark. However, Hone and Tracey decide to investigate instantaneous gas, and find that this option would reduce the running cost to $620 per year. Their new choice complies easily with the proposed Building Code requirements. The instantaneous water heater is actually cheaper to install than the one suggested by their builder, thereby making their building project cheaper as well as delivering ongoing savings. The payback period is nil.

Case study 3:

The Smith family want to bring a large homestead near Dunedin up to present day standards. Using a conventional electric storage system would not meet the new Building Code requirements, and would cost $1,500 per year to run. The Joneses look at the other options. They decide to fit a shower drain heat recovery system for $700 that will save them nearly $400 per year. They also add a solid fuel hot water booster (wetback) to their new wood burner at an extra cost of $300, thereby saving $200 per year. They prefer these two options to a heat pump water heater, which would save an equivalent amount (just over $600 per year), but has a higher initial cost. When both their choices are installed (at a total extra cost of $1,000), the resulting cost of a year’s water heating for their homestead will be $900 per year, giving a payback period of less than two years.