Two months ago I moved into a new house and I feared the worse. The last house I lived in didn’t look that efficient: It was effectively a tent made out of wood.
Somehow though, probably thanks to its gas fired hot water, and despite my daughter’s hair dryer, the electricity bill never seemed that big. There was no air con –there’s not much point in a tent – and consumption rarely moved above 10kWh in a single day, even with four inhabitants.
This new house is a different challenge. There is only two of us now, but it’s off grid gas and off-grid sewage, which means that it is pretty much all electric. And there is a swimming pool. So every time we use water, a pump switches on, the pool has to be kept clean, the hot water system is like a very big kettle, and there is even air-con, and electric heaters – neither of which we have used yet.
My fear was that the daily usage of the household would be somewhere between 20kWh and 30kWh. With the two of us, it’s not so bad, and we can usually scrape in at around 15kWh. But with guests, many showers, and the oven in regular use, it’s been damn hard to keep it under 30kWh – and that is without the air-con or the electric heaters.
So, what to do? How much solar should I put on the east-west facing roofs (pretty clear but for a line of trees that would brink sunset to any panels an hour early).
And when I do put in solar PV – that’s inevitable – should I start planning ahead for the day when I might add an electric vehicle, or add battery storage. Or both.
And if I am thinking about battery storage – what do I want to get out of it? Do I want to use it as a revenue raiser, or to offset more bills. Do I just want to install excess solar power on a matter of principal, or do I want it as back-up (it’s on a semi-rural line that faces regular blackouts – the previous owner had a generator installed just for that purpose.
Should I use solar PV to heat the water, or add a solar hot water system – flat plate or evacuated tube? Is a heat pump an option?
Should I change the pool pumps? Actually they are pretty efficient and run about 0.3kWh, but is there some way of using them less?
And what should I do – if anything – about the heating options. The electric heaters are in bizarre places – the study and a corridor – and the reverse cycle air con is in the main bedrrom and the open living area. Is there some way of making the insulation better?
I’m not really worried about air-con. The house is sitting high on a ridge and it gets plenty of breeze, and there are fans in most rooms if it gets too still and sticky.
It occurred to me that I am facing the same questions that confront many in the community – so many options, so many different brands, so many technologies – particularly in battery storage – that are difficult to grasp.
The first thing I did though – and one of the reasons why I am across the daily usage – is to install a monitoring device. I got one from Solar Analytics which gives me a monthly, weekly, daily, and intra day readings – right down to 5 second intervals.
This has given me remarkable insight into the variable or our demand. For most of the day, not much happens. The pool pump comes on, and raises demand a bit, and ditto in the evening with the lights (mostly LEDs).
The jump in the kettle is a bit of a shock, but nothing compared to the hot water, which comes on around 1.40am and will gobble up 7kWh pretty quickly, or in this case above, more than 10kWh in just a few hours.
But it gives me a few ideas about my demand profile, and what my options might be for solar, and eventually battery storage, and how I might change my consumption patters. More on that at another time.
Giles Parkinson is founder and editor of One Step Off The Grid, and also edits and founded Renew Economy and The Driven. He has been a journalist for 35 years and is a former business and deputy editor of the Australian Financial Review.
This post was published on May 4, 2016 9:39 am
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A most useful approach Giles - a step by step guide. I look forward to the next instalments - and the answers to the many questions raised. In the end it may become a manual for home owners (I hope).
Knowledge is power - only after I got my solar installed did I really appreciate where the juice was flowing.
Word of advice on the pool pump: figure out what its Qmax is (how many litres per hour) and then run it according to the size of your pool.
My pump is rated to 0.875kW (875W) and it has a Qmax or around 19,000L. My pool is 31,000L so in off-season I only run it enough to theoretically cycle the water once i.e. 90 minutes. In summer I'll run it more often to take account for more activity, but then the sun is shining when that happens :)
I am also living in an older house with only me and my wife. I am currently averaging about 20kWh with my wife home all day. What to change is an ongoing thought problem. Below is my personal opinion.
The monitor is a great start. Get a home energy audit to see if there are any glaring issues. Energy efficiency pays, but it sometimes takes a long time. Insulation is not sexy but is reasonably priced and works forever. Here in Nevada the wind does not provide much cooling. Every watt I expend in the house needs to be taken out again via the AC system, so energy efficiency matters.
For a small investment, LED light bulbs will pay back eventually, but they might take a long time. An induction cooktop is about 2x as efficient as the standard electric hob. Depending on the age, the hot water heater should be replaced with a hot water heat exchanger, for a 3x to 4x improvement in efficiency, or a point-of-use system if the usage is low enough. The same logic applies to the refrigerator, washer and dryer, the AC unit, and perhaps even the pool pump. New units can be much more efficient than ten or twenty years old units.
Solar is now cheap, and should be a quick decision. How much to get is something that you need to determine. If you are attached to the grid, and can afford it, get a system that will supply your daily load in the middle of the winter. While you may be giving some of your electrons away right now, or getting a horrible FIT, but you may get that electric car eventually. Planning and installation is a large part of the cost if you do not do it yourself, and will be less if only done once.
Once you have solar, run the high demand items when the sun is shining. You may even 'need' to run the air conditioning. Storage can wait, as it seems that the prices are still dropping rather quickly. If you want storage now, only get enough to kill the peak demand if you have a time-of-use tariff. Eventually you may get enough so your solar panels can get you through an entire day. Currently getting more than that does not make sense unless you are fully off-grid.
Great, practical stuff, Giles. Are you a member of the ATA? They are the publisher of ReNew, a quarterly magazine packed full of energy efficiency and renewable energy information. Members have access to the complete back issues, which are searchable on line. For example, I recall a discussion a few years ago about making water supply pumps as efficient as possible.
I like your description of the house as being like a tent. Such houses are far too common!
Our architect gave us some good advice when we did a big renovation - live in the house for a year and by then you'll know what rooms need heating in winter and what rooms need cooling in summer.
what is the biggest power hungry device in the household? You mentioned it at the end the hot water cylinder - use it to your advantage with our ismart hot water controller - out last an intelligent hot water controller, where you can heat the hot water when you need it and use it as a liquid battery - go to http://www.ismarthotwatercontroller.com.au
Buy a smaller ,but smarter and warmer home and install a solar hot water system and a 5 kw solar power system. Use a new A/C for cooling and heating . My solarhart hot water system is about 22 yrs old and has 2 x hot water valves replaced (friend ) and 2 x washes. Its on a old house (26 degrees North facing roof) on stumps , next to my 21 yr old Aust. Red Cedar Tree , which blocks winter sun until it drops its leaves . Heating water is the Big power user (40% bill ).
Step 1. Call in a CEC accredited Stand Alone Power Systems Designer to work with you, evaluating your evaluated load profile, roof tilt and orientation, peak sun hours, and shading, to design a suitable solution. Most will also be Grid Connected Design accredited as well.
Step 2. Determine the largest single phase Inverter that your electricity distributor will permit a residential house to connect to their distribution lines. In QLD, Energex allows up to a 5kW inverter.
Step 3. Following the Clean Energy Council guidelines, determine the maximum size array that can be connected to the above inverter. For a 5kw nominal output inverter, this is 6.5kW of panels. For a 4.7kW inverter, this is 6.251kW of panels. Oversizing your grid connected array beyond this is not illegal, but against the Clean Energy Council guidelines, which all accredited Designers and installers must follow. It will void the entitlement to the small scale renewable energy certificates, worth around $5000 for a 6.5kW solar array, and reduce the efficiency of your system, by having idle panels as the inverter will max out and not use their output in peak sunlight hours.
You have many options as you shared in the article. If money is not too scare, then an evacuated tube solar hot water system would be an excellent investment. It would reduce your electrical load considerably. Much more than flat panel solar hot water, and electric heat pump options.
You could also install an Off-Grid Solar Array alongside your grid connected one, if you have the roof space.