Wattwatchers’ Program Manager and distributed energy technology specialist Tim McCoy takes time out from the daily grind to fine tune energy optimisation in his home. It turns out that his smart energy monitoring can help with his consumption of gas for central heating as well!
Like most Australian households, we have been watching the recent energy crisis unfold with great concern as to what our energy future bills might look like. We live in Melbourne where winter became much colder much earlier this year than we’ve ever experienced before, with a cold snap in late May. It’s generally much more common to have our coldest few weeks coincide beautifully (depending on your point of view) with the start of the school holidays in early July.
We live in a fairly typical brick veneer home built in the late 1970s to early 1980s which is moderately insulated, has traditional single-glazed windows and energy efficiency somewhere better than a tent, but well below a modern 6+ energy star home.
Also, like many older properties in Melbourne, our heating is a gas central-ducted system, with individual vents that can be closed manually… but generally aren’t. It was replaced about 5 years ago with a modern unit when the old 15+ year old system died suddenly, so at least it’s in good condition. Our cooling is from a separate central ducted evaporative system, so there are no reverse cycle air-conditioners in the property—but we are planning this for the near(ish) future. We like to live in sensible comfort. So, for the most part, we end up turning on the central heating system when the cold weather begins and it runs 24/7 based on a single central thermostat.
Inspired by the great ideas and discussion from the community at My Efficient Electric Home, we have been sealing up doors and an old fireplace while looking for other air gaps. But the real experiment this year has been seeing how low we can run the overnight temperature while being comfortable, and also trying to understand what sort of energy efficiency envelope we can maintain and improve.
Over the past few years, we have generally run the heating system at around 21–22°C all day in winter, and sometimes turned it down to 19–20°C overnight. This was very comfortable, but rather “I don’t want to talk about it” expensive to run! Since Covid turned the world upside down, we have a family working and studying from home, so continuously heating the fully occupied home feels slightly more justified.
This winter season, we have found through some simple changes that a new setpoint of 18°C during the day and 16°C overnight is still comfortable for everyone. Although we aren’t exactly sitting around in shorts and t-shirts.
But the question gets raised: how can we monitor our gas usage, with bills that only come every two months, much to our nervous anticipation in the winter months. It turns out that our Wattwatchers Auditor electricity monitoring device with the MyEnergy app does a great job of making our energy efficiency and gas consumption visible by looking for the electricity consumption spikes from the electric fan that pushes the warm air around when the ducted heating system is running.
Using the MyEnergy app, we have been able to work out that our overnight standby or base load varies from around 80W to 150W when only our always-on and standby appliances are running. The easiest way to do this is to look at the MyEnergy Live screen right before going to bed to see the standby consumption of the home when everything should be turned off.
The live update features of the MyEnergy app also helped us to identify that the central heating system uses around 1kW when running, so it’s really obvious when the system is cycling on and off.
By looking at the charts in the MyEnergy app early in the morning each day, we can get an understanding of how many times the heating has come on in the night from these spikes. In the MyEnergy app, when looking at a history chart for “today”, you will see only the consumption between midnight and the current time. So by looking at around 7am each day we can identify overnight consumption and ‘vampire’ loads much easier. But in this case, we are actually more interested in the big spikes from the central heating system when running.
Because it’s on a shared electrical circuit, our gas heating isn’t being directly monitored by our Wattwatchers device. So, we are just using the charts from the History Grid section of the app to see the spikes. Provided we didn’t put the dishwasher on before bed, the only thing that will drive substantial electricity use overnight will be the fan for the central gas heating system.
In this first example, on the 20th of May 2022, the overnight low was 9°C and our home cruised through the entire night without the heating coming on even once before 6am. It only came on at around 6.30am, before everyone started getting up for the day.
This seems to indicate that down to an outdoor temperature of about 9°C–10°C we can maintain our indoor temperature of 16°C passively for most of the night. That feels like a win!
By comparison, on the morning of the 4th of July 2022, when the overnight low was about 2°C, the heating came on 7 times between midnight and 6am. So, our home wasn’t performing very well when the outdoor temperature was particularly low. But at least the system wasn’t running continuously and was heating for 10–15 minutes and cycling off for about 30–45 minutes—less than it used to.
These results show the expected correlation between the outside temperature and how hard the heating has to work overnight. It’s clear that we can’t passively maintain the temperature of the house without substantial overnight heating when the outside temperature is below about 8°C. But we have been able to confidently make some changes to our temperature and comfort settings and see the results well before our next gas bill arrives.
We are also planning some bigger changes in the future, like installing reverse cycle air conditioning in either central or multiple split systems. But for now, our research continues into the best options for this major expense while we run the current gas system as best as we can.
The benefits of the Wattwatchers near real–time energy data are clear in this situation, as it’s important to be able to get feedback as quickly as possible when making some of these energy efficiency changes.
Traditional smart meter data would only make this data available in 30 minute blocks, which makes seeing the on and off times of the heating system much harder compared to the 5 minute Wattwatchers data resolution, which makes this very clear. To illustrate, see how, in the example below, the 30 minute consumption blocks start to blend together compared to being able to immediately identify the times when the heating ramps up and back down again in the 5 minute data.
Wattwatchers data is also being continuously updated, so the most recent 5 minute interval is available immediately in the MyEnergy app compared to a smart meter portal, which might be anything up to 24 hours behind depending on when we looked at the data.
I expect that all of this effort might reduce our gas consumption by 10–20% compared to last year, which should see our bills reduce slightly. Though this won’t be helped by the ever increasing gas rates and an early start to a harsh winter. This sort of testing and analysis also serves as a good baseline of understanding of energy patterns when the system is working well. Any sudden increase in electricity consumption, such as seeing the heating run for longer and longer periods of time overnight would indicate a problem we need to get fixed.
To get alerted to any unusual electricity consumption, our MyEnergy Energy Budget notifications are set up to send us a push notification based on 50% and 80% of a $100 per month target, and provided we don’t get the 80% notification more than a few days before the end of the month, we know everything is running normally.
All of this really adds up to help us manage our energy consumption and efficiency far better than using just smart meter data or bills alone.
What does your overnight consumption look like and what improvements can you make?