grand/not-so-grand designs of the sustainable kind
Author: must be thrifty
Buying a house on a single-person income is never easy, but must be thrifty did it anyway in 2009, when interest rates were at a record low. Now that interest rates are going up and house prices are going down, she's bracing herself for some serious scrooging...
Whoever invented ducted floor heating is evil because now I have to look at these patch-ups every day:
Yep, we got the carpenter to nicely fill up all of the ducted heating holes in preparation for underfloor insulation. Unfortunately, due to differences in the age (and, sometimes, the species) of the wood, the patched-up bits do not match the existing floor, even after using the same Livos stain.
While we had solar panels, we shifted our electrical load to daytime use as much as possible. The dishwasher, hot water service, and washing machine all had timers or delay functions so we were able to run them during the middle of the day, making the most of the sun while it was out. For 100 days while we waited for our battery install, we consumed 771.73kWh, 390.48kWh of which was from the grid and 381.25kWh was from our solar panels. In other words, our solar panels supplied just under half of our energy needs.
And how does our current daily grid power consumption compare to 2015 figures for August to October?
Hardy ha ha, another geeky graph:
In 2015, we used gas for our our hot water service, stovetop cooking, and heating. Since our 2015 and 2016 daily grid power imports are very similar, the solar power we consume on site is roughly equivalent to our heat pump, induction cooktop and split-systems’ energy needs.
But the million-dollar question is: how have the Enphase batteries affected the numbers?We installed Enphase batteries on 13 November 2016; our power usage has dropped considerably since. In the first half of November, we imported an average of 2.22kWh per day from the grid. In the second-half, post-batteries, this number dropped to 0.8kWh per day. And in December, as summer shines down on our roof, we are now drawing an average of 0.644kWh per day.
We will always be drawing a small amount of power from the grid, as the batteries aren’t designed to take all of the immediate load like an uninterruptible power supply (i.e. offgrid systems), but 0.644kWh is pretty darn good.
So, pretty exciting stuff.
And finally, here’s a lovely table from our Powershop account which is our year in review:
Enphase batteries are AC-based (rather than DC) and hence integrate really well with our AC microinverter system. It has many pluses, such as compact sizing, modularity and, according to Renew Economy, ‘a depth of discharge greater than 95 per cent, an ambient operating temperature range of -20°C – 45°C and a warranty of up to 10 years or 7300 cycles.’ After 7300 cycles, Cheap Geek expects them to still be operating at 80% capacity.
Install took just over 5 hours (1 hour per battery) and the batteries were charged by the end of the day. We now have somewhere between 5.7 kW and 6 kW to draw from during sunless periods. It’s too early for us to tell whether the batteries will remove our need for coal-powered grid electricity completely, so watch this space…
Now that we have surplus free clean electricity from our solar panels, it makes sense to power our garden tools with batteries instead of petrol. Cheap Geek took advantage of the Masters fire sale and bought an electric lawnmower and line trimmer. He’s used both a few times now. The mower was used on regularly cut buffalo grass while the trimmer was used on a neighbour’s neglected garden as well as our somewhat neater yard. Here are his thoughts:
The electric lawn mower is quieter and lighter than its petrol equivalent*. It also doesn’t have a pull cord and therefore does not require muscle to start; if you can make a fist with your hand, you can turn it on. Cleaning is easier too: no need to worry about petrol leaking or accidentally burning yourself against a hot engine.
The height adjuster on the electric mower is not as fine as the old petrol mower, but it is good enough for domestic use on buffalo grass.
The electric line trimmer is also quiet to use. The noise mainly comes from the sound of the trimmer line hitting the grass. It is, however, heavier than petrol models due to the weight of the battery. This particular model comes with a shoulder strap, which can take some of the load off the arms when necessary.
AND ANOTHER THING
The batteries provided ample juice for our block (and some of the neighbour’s garden as well), and you can buy bigger batteries where needed. When the batteries run out, the tool just stops; there is no noticeable decline in power before this happens. Recharging takes about 1 to 1.5 hours, and should be done while the sun is shining.
Our old petrol garden tools are still in good working order. My dad gave these to us when we first moved into the Mustbethrifty House; they were old models that he had repaired/serviced. Dad will be taking these back and sending them onto family who don’t have solar panels. I’m not sure what to do with the jerrycan though.
Ripping out the gas meter was logistically unfun. It took many phone calls, emails, and Facebook complaints before my gas provider figured out that I didn’t want to disconnect from the electricity grid (I don’t even have an electricity account with them) and that I just wanted a Victorian Gas Abolishment Form. My gas provider also tried to tell me that meter removal would cost upwards of $500, when, in reality, it cost under $60. I’m not sure why it was so difficult for customer service to action my request. Maybe gas meter removal is still too rare an occurrence? Maybe other folks who switch to all-electric keep their gas meter and continue to pay their service-to-property charges?
Anyway, the gas is gone and good riddance.
Meanwhile, winter has come; we’re cranking up the main split-system in the living areas for a couple of hours on most nights, and sticking to these areas. In the morning, our bedroom split-system turns on briefly to help us get out of bed. It’s really, really cold in the bathroom, now that there’s no ducted heating coming out of the vents. (Note to self: must get onto draft-proofing and double glazing this room.) Cheap Geek has timed the hot water to turn on during the middle of the day, in anticipation of free solar-generated electricity. And I’m getting used to cooking on the induction stovetop.
During this period of all-electric (no gas consumption), we used an average of 9.84 kilowatt-hours per day (20/5/16-5/8/16), compared to last year’s average of 5.63 kilowatt-hours per day (20/5/15-5/8/15) when we were using gas for heating/cooling, stovetop cooking, and hot water.
While waiting for the solar panel install, we had some roof maintenance done. The work is guaranteed for ten years, which hopefully means no solar panels will need to be removed during this period. Cheap Geek and my dad also took away the unused satellite dish that was bolted to the chimney; it would have been extremely hard to remove the dish with solar panels underfoot!
Thirty-two solar panels (Q.PRO-G4 265) were installed over three days. Due to our roof orientation and overshadowing in summer, Cheap Geek opted for microinverters instead of the traditional centralised inverter. There was the option of having a central inverter with power optimisers; these work better at extreme temperatures (i.e. warmer climes) and are the more cost effective option in commercial/larger arrays. However, we live in Melbourne and have a domestic system. Cheap Geek also preferred the safety of AC current running across the roof.
The panels started generating electricity on 6/8/16. So far, they’re pumping out anything between 4.19 to 27.3 kilowatt-hours. We haven’t got batteries yet so we are still drawing power from the grid between dusk and dawn, an average of 5.04 kilowatt-hours which is almost a 50% reduction in grid-electricity consumption. It also brings our grid-electricity consumption below what we were using in 2015, which means that our solar array is offsetting all of our energy needs for heating/cooling, stovetop cooking, and hot water.