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Home > Info > Building design, construction and renovations > How we took our power bill from $900 in winter to $20 in summer.

How we took our power bill from $900 in winter to $20 in summer.

Cloud based information of my Smartnow meter

Background
In 2002 we built our house in the mild ocean moderated climate of Hobsonville, Auckland, with preformed concrete walls complete with built in insulation and concrete floor construction to all levels, topped off with a flat poured concrete roof waterproofed with flamed on industrial bitumen.


We installed two large low tech solar hot water flat plate collectors plumbed into a 415 litre hot water tank with the usual 3 kW element plus 12kW of booster elements as we planned to use the HWC as the heat source for the under floor hot water heating systems. At the time, electricity was about 10 cents a kilowatt (now 27cents circa early 2013) so we didn’t mind if the bill doubled over winter to have a warm house.


We did consider double glazing until the quotes came back, so settled instead for laminated glass to all windows and doors. We fitted halogen down lights and energy saving light sensors to all transit areas, hallways and walk in cupboards etc. The house wasn’t oriented at all for solar gain but more for privacy. A late decision was made to add a open wood burning fire, but it was too late to install plumbing for a wet back!


The Problem
While we had built a house that was "greener" than many at the time, reliance on electricity as the key energy source became an issue as over the next ten years the cost of power almost tripled in direct response to the governments introduction of a “competitive electricity market”. It got to the point in May 2012 that when I turned on the 12kw of booster elements in the hot water cylinder for winter I was already dreading the power bill that was to come! When my bill climbed to $900 in mid winter, I knew I needed to take action fast!!


The Solution
I went through a three step process to lower the electrical consumption of the house.
Phase One: Installed LED lights to replace ALL those hungry halogens. Typically a 5 watt LED replaces a 50 watt halogen. This had a less effect than I hoped but certainly made me feel better when the kids left the lights on!


Note: be sure to source LED’s with Cree SMDs as they are the best and brightest – specify warm white as two colour temperatures are available, the other being cool white which is like being in a fridge! Buying the same model from one supplier reduces colour differences and may increase your buying power for discounts. Even the warehouse is carrying a reasonable range these days!


Phase Two: I wanted to cut the cost of the energy for the domestic hot water and under floor heating. I considered a gas boiler but we didn’t have gas mains in the street and my neighbour whom had a gas boiler, had to change his large gas bottles very ten days. After more research I came across specialist hot water heat pumps (HWHP) that extracted energy from the ambient air and supplied hot water. They claimed a 3 to 1 energy conversation, so I could use electricity but drop my heating cost for that application by 66%! I looked at large unist for the under floor and hot water application and smaller units for domestic hot water only. In the end I went with a unit that output 3.7 kilowatt for a draw of 950 watts. This marvellous invention dropped my power costs by 50% in winter! Happily it was able to provide some energy for the under floor heating except the coldest month when the standing loss was higher than the output. In one month my bill went from $900 to $450 which gave me a saving of 10% of the capital cost in a month! (July vs. August)
We went with a domestic HWHP from http://www.econergy.co.nz/ , see my testimonial here http://www.econergy.co.nz/testimonials.html They were easy to deal with and offered finance!


Note: On average, 30% of a normal electric bill is for hot water heating if you have traditional hot water cylinder with an electrical element. A HWHP are designed to plumb into existing HWC’s.


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