Randall's home energy descent plan!

An interview with Village Power member Randall Pearce by Robin Gale-Baker.

Robin: Randall, I know that over the last 10 years, you've been very active and successful in reducing your home energy consumption. Can you expand on the reasons that drove you to embark on your home energy descent plan?

Randall: In 2013, I decided to work out our household carbon footprint with the intention of driving it down a lot. I was concerned about carbon emissions and wanted to measure how much we were generating and to try to reduce our contribution. We switched to sourcing only 100% green electricity for any imports. I also wanted to reduce our high energy bills, but still wanted the house to be comfortable to live in and wanted to improve and maintain the value of the house, for whoever was going to live in it down the track.

Robin: Can you tell me about the construction of your home and how many people live in it?

Randall: These days only my wife and I live there. We are both retired so we are home a lot during the day. The house is a large split-level house of fairly basic construction with 5 bedrooms and two bathrooms. It was originally built in 1951, but has been progressively extended towards the back in the 1960s, 70s and 90s. It's built on stumps, with timber floors, and a timber frame with concrete and stucco exterior cladding. The windows were all thin single glazed, with some windows having old metal frames. The original front section has a tiled gable roof, but all the extensions have flat metal deck roofing. The extensions are timber-framed with textured cement sheet external cladding.

Robin: What did you begin by monitoring?

Randall: As a work mentor once taught me, ‘If you can't measure it, you can't improve it’. So I began by preparing a spreadsheet of household monthly energy consumption and costs.

I set a benchtop Nylex clock thermometer on the kitchen bench to display both indoor and outdoor temperatures. This is a great way of observing how much heat the house loses overnight. It used to lose 8 degrees on a cold night, with the heating off. After 10 years of my efforts, this has now reduced to only 3 degrees. Also, in summer it tells us when to open and close windows for maximum cooling effect.

Next, I found where all the external air draughts were coming from. This led to a long list of simple opportunities for sealing them up, to reduce energy wastage. Major air leaks were through external roof air vents from each bathroom, and through the kitchen exhaust fan. Eventually, I had these sealed up using Eco-tastic exhaust vents, with dual flap vents which spring shut when the fans turn off.

Robin: What happened from there?

Randall: Over the first 5 years we installed gas-boosted solar hot water heating, a 3 Kw solar PV system, a high-efficiency fridge, converted all lights to LED globes and replaced 2 large windows with double glazed units. All of this reduced energy consumption about 20%.

Robin: What was the next step?

Randall: We’d had a silent and comfortable hydronic heating system with gas as the heat source. This was heating the whole house, and gas bills had risen to nearly $2,000 a year.

Going into the winter of 2020, the 35 kW gas boiler failed and was going to cost $3,500 to replace it. Fortunately, we had just installed a 7kW Daikin reverse cycle heat pump air conditioner for cooling, but I was skeptical that this would be enough to keep us warm. Since its efficiency is around 400%, it turned out to be fine, with the addition of two 1 kW thermostat-controlled electric convective heaters to hold low temperatures in the bedrooms, and by not heating the bathrooms and unused bedrooms. I was impressed to find that we had saved $1,000 a year by only using electricity instead of gas to heat the whole house.

Water leaks then led us to replace most of the metal deck roof, so we had this fully re-insulated at the same time. At this time I discovered that many of the micro-inverters on the 7-year-old solar array had failed, and so its maximum output had dropped to 1 kW. Solar Gain installed a very satisfactory new 10 kW solar system, fitted with DC optimisers on each panel, due to substantial tree shading around us. I had a small current transformer installed with it, so we could monitor household power usage in real time.

We finally had the two old 1950s front bedrooms completely renovated by re-plastering, re-insulating walls and ceilings, and installed new double-glazed windows. All our windows now have either honeycomb blinds or heavy drapes with pelmets above them to prevent convective heat losses.

I took advantage of the Covid lockdowns to spend days insulating underneath the entire house floors by myself, using bags of R2.5 Ecowool insulation picked up from Bunnings. This has noticeably raised the winter floor temperatures underfoot and has further reduced the energy used for house heating.

Robin: What has been the result?

Randall: After that first 8-year period our net house energy bills dropped from $2,562 to $560, so we were saving $2,000 per year in energy costs. This has helped to offset the capital cost of the upgrades, but it has also improved to value of our house as an asset.

Robin: Tell me more about reducing your carbon emissions to zero.

Randall: We had reduced gas energy usage to just $100 a year, but still had a gas bill of about $450 per year, due to the daily connection charge.

We were also still emitting 4-5 tonnes of CO2 a year from gas boosting of the solar heated hot water, and via a rusty old gas cooktop. Our son had very badly burned his back from a gas cooktop, and we nearly blew up the kitchen a couple of times, due to gas leaks. There had also been gas leaks from our, and our neighbours’ external gas meters.

So, we finally installed a Reclaim heat pump hot water system and electric induction cooktop, and had the gas connection “abolished” all together. We now have a safe house and have eliminated household carbon emissions altogether. Net energy cost savings have been about $100 a year from that change, since the extra cooking loads in the evening have added to our electricity imports.

In future, I’m hoping to be able to use energy which we have exported during the daytime to a community battery to cover this out-of-hours electricity consumption.

Robin: What were your carbon emissions 10 years ago?

Randall: Our household emissions had been a huge 57 tonnes. This is very significant compared with our small car, which does 8,000 km per year, and releases about 1 tonne of CO2 emissions. That is why I haven't focused on changing the car at this stage.

Robin: What would your advice be to those wanting to follow in your footsteps?

Randall: Get a genuine good quality PV system, as large as possible, with a good phone app which can run all the time. If you can see solar electricity production, household consumption and exports in real time, you can control when you use appliances throughout the day to make best use of your generated solar energy, particularly during the darker rainy days of winter.

Also, always buy appliances which allow you to keep your instantaneous power use to a minimum. Our aircon heater/cooler can be set to use just 1 kW on its quiet setting, and the hot water heat pump only uses 1 kW for 2 hours in the middle of the day, when we have spare capacity.