The en­ergy ef­fi­cient home

Adding up the run­ning costs of a house over the av­er­age term of a mort­gage makes in­vest­ing in en­ergy ef­fi­ciency the prover­bial no-brainer.

Element - - Contents -

What is your home cost­ing you?

Ear­lier this month, on the wharf out­side the Viaduct Events Cen­tre, Sam­sung threw open the doors of its Home Smart Home (pic­tured above) – a re-con­fig­urable bach de­signed by ar­chi­tec­tural whizz-kids Jas­max, and stuffed with ap­pli­ances that use just a frac­tion of the elec­tric­ity and wa­ter that your ap­pli­ances at home man­age to plough though.

Elec­tric­ity, gas and wa­ter bills are no longer just a mi­nor bump in the monthly fi­nan­cial road. For most they now have to be se­ri­ously bud­geted for.

It begs the ques­tion: when we buy a home, why don’t we mea­sure its run­ning costs?

The av­er­age home in New Zealand uses around 25kWh of elec­tric­ity each day, equat­ing to just un­der $2500 worth of power each year. Mul­ti­ply that by 25 years, the term of the av­er­age mort­gage: $62,500, and con­sider that this cost doesn’t take into ac­count the in­evitable and de­press­ing an­nual price rises.

En­ergy ef­fi­ciency

First things first. En­ergy ef­fi­ciency is key. In a re­cent re­port from the World Fu­ture Coun­cil on how San Francisco can reach 100% re­new­able en­ergy, a full 50% of the means to achieve it came down to en­ergy ef­fi­ciency. And so it is with your home.

The ‘Zero En­ergy Home’ in Point Che­va­lier, Auck­land re­quires no gas or elec­tric­ity for heat­ing, re­ly­ing solely on a con­crete pad which ab­sorbs heat when the sun is shin­ing, and slowly re­leas­ing it again in the evening when it is re­quired. This, com­bined with good in­su­la­tion and smart ven­ti­la­tion, means that a heat source sim­ply isn’t re­quired.

While in­stalling a con­crete pad may not be pos­si­ble un­less you’re build­ing or ren­o­vat­ing, in­su­la­tion can be in­stalled, and draught-proof­ing can be car­ried out.

Dou­ble glaz­ing can also be retro­fit­ted, the ad­van­tages of which in­clude be­ing warmer in win­ter and cooler in sum­mer, re­duc­ing con­den­sa­tion and cut­ting noise.

In­su­la­tion and heat­ing

Be­fore boost­ing your heat­ing sys­tem, carry out en­ergy ef­fi­ciency mea­sures and you’ll find you might need a unit with a smaller heat­ing ca­pac­ity. When you con­sider that (elec­tri­cal) space heat­ing makes up almost a third of the av­er­age power bill, it’s worth get­ting the smaller model. In de­scend­ing or­der, choose pas­sive so­lar op­tions, wood or pel­let burn­ers, heat pumps or flued gas heaters. Avoid panel heaters, oil-filled col­umn heaters and es­pe­cially un­flued gas heaters.


It’s go­ing to cost you the guts of $7000 – $10,000 to do it right, but so­lar photo voltaic (PV) pan­els are go­ing to cut a swath through your power bill. Wait un­til you’ve made your home en­ergy ef­fi­cient and re-mea­sure your power use be­fore choos­ing what size ar­ray you need. Get a slightly larger in­verter than your pan­els need, be­cause in fu­ture you may want to add more pan­els to charge your elec­tric ve­hi­cle. Pro­vided you choose the right-sized ar­ray for your needs, PV should pay it­self off within eight years.

Wa­ter heat­ing

Another third of your en­ergy is used for heat­ing your hot wa­ter. For­tu­nately the days of the tra­di­tional hot wa­ter cylin­der are draw­ing to a close, as they are be­ing bul­lied out of ex­is­tence by their rad­i­cally more ef­fi­cient suc­ces­sors.

Top of the list are heat pump wa­ter heaters, which will im­me­di­ately slash your wa­ter heat­ing bill by up to two thirds and can be in­stalled for as lit­tle as $2500.

So­lar hot wa­ter, ef­fec­tive and ef­fi­cient while the sun is shin­ing, is nonethe­less ex­pen­sive to in­stall so has a rel­a­tively long pay-off time.

Gas hot wa­ter, whether through stor­age sys­tems, or ‘on de­mand’ sys­tems, come next for ef­fi­ciency, but rely on fos­sil fu­els.


Elec­tron­ics take up around 18 per cent of power us­age. If you have so­lar power, charge all your mo­bile de­vices dur­ing the day. Turn off ap­pli­ances at night, as left on standby they are just wasted money. Ap­pli­ances with the Blue En­ergy Star mark are among the top ten per cent for ef­fi­ciency.

Re­frig­er­a­tion takes around 11% of the elec­tric­ity used in your home. Over the 15-year life of a fridge, an ef­fi­cient model will more than pay for it­self.


Ever burnt your hand on a bulb? That’s wasted en­ergy, con­verted into heat rather than light. It’s also why light­ing makes up eight per cent of your en­ergy use.

Chang­ing your bulbs to LED mod­els will save 80% of that en­ergy and last for years. Over the life of the bulb, it will save around $110 dol­lars, dwarf­ing the ini­tial in­vest­ment.

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