A green revolution — Part 3
The solar panels
We made the switch to an electric car and we changed our gas central heating for an energy efficient air-source heat pump. The final instalment of this “adventure” (at least in terms of technology changes) is the solar panels.
Along with the heat pump, we ordered a 3kW solar panel array, to be fitted by the same people, the lovely team at EcoWatt. 3kW is as big an array as you can get before you have to start paying TVA (VAT) on the panels in France, which makes them about €100 more expensive each, so most people start with 3kW. Although there is an argument for going further, as the VAT on the panels is not all that much when you consider having to pay the fitters to come back a second time if you decide to fit more, but each case will have its own economic pros and cons — it’ll depend on your household.
Placement
Of course the first thing you need is a decent, south-facing surface of some sort, as free from shade as possible. In our case we have a large roof pitch facing virtually south south west, so while this isn’t ideal — there’s a large oak that shades the evening sun in winter and a block of masonry (my office) that shades the morning sun a little first thing — it’s plenty good enough to get decent production. It’s worth noting of course that it doesn’t have to be a roof. If you’re fortunate to have a large open space near your house, such as an acre of lawn, you could run your panels along the north edge on the ground, which clearly makes them far easier to fit and maintain. But in most cases, the roof will be the only sensible place to put them.
Anyway, EcoWatt’s fitting team came over in April and had a good look, climbed up on the roof, took a load of photos and concluded this large pitch, being well-constructed and part of the original house, would be the best place to put the panels. With that decided, we could go ahead and apply for the necessary planning permission.
Fitting
Unfortunately, due to the pandemic, we had to wait far longer than usual for the planning permission, on account of the government offices in Nîmes getting shut down for a couple of months. We missed the most productive parts of the summer months for 2020, but never mind — it was nobody’s fault. So in August the fitters were finally able to come over and fit our 3kW array, composed of 10 individual panels generating 300W each at peak output (in laboratory conditions — more on that later).
These days each unit comes with its own solar inverter, which is good — this used to be a centralised piece of kit, rather expensive, and if it broke then all your solar production was lost until it was fixed. With modern panels, you lose the inverter on one panel the other nine are still producing, you can call out an engineer to replace the broken inverter and meanwhile you’re still at 90% generation capacity.
It also simplifies fitting, essentially all your fitters need to do is fix the panels to the roof, wire them together, feed the cable back to your main electricity fuse box and wire them in.
Optional extra — monitoring your production
We opted for a monitoring system. This wasn’t cheap, and it really isn’t necessary, but because we had no friends with PV arrays already and we didn’t really have a clue how much energy things in our household use, it has proven invaluable for understanding and managing our consumption. We were sold a system called Elios4you, manufactured by an Italian IoT company called 4-noks. It works very well and you can do things like adding “smart plugs” that switch themselves on and off according to current production, can be remotely controlled from the app, and so on.
However, I have since learned there are open source and standards systems for the same thing, so you might consider those instead of a closed-source corporate solution like the 4-noks one. Ultimately, I guess you’re at the mercy of your fitter as it comes down to what they’re prepared to fit, unless you know how to do this stuff yourself! But I’d certainly encourage folk to take a good look at Open Energy Monitor and talk to their fitter about it before deciding on a product.
And just to repeat, you absolutely do not need a monitoring system at all. You can just choose not to look and carry on with your life, which is especially true if you have a fixed-rate electricity contract. If you’re using virtual battery technology, as I wrote about last time, then you won’t “waste” any of your production anyway, so what does it matter?
Changing contract
One of the interesting things about getting solar panels and working from home is you realise HP/HC electricity as it’s known in France, “Economy 7” in the UK — essentially cheap electricity at night in return for expensive electricity during the day — is simply not worth having. It is suddenly desirable to use electricity during the day and you find the savings of running certain activities at night are no longer worth the higher rate you pay while topping up your solar production during the day.
Each household will have to do their own study and do the maths, for people that go out all day to work in an office this may not be true, but for us we’re clear winners if we pay a flat, lower, average rate for our electricity. It also means we don’t find ourselves running out and unplugging the car if solar production falls below 1.5kW and silly stuff like that. It means reprogramming all your devices that assume electricity is cheaper at night to run during the day, but that’s easily done and it’s a one-time pain.
Actual production
I look back at my previous article stating we will have “almost no electricity bill for the next ten years” and laugh at my naivety! As, probably, did anyone who already has a PV array. Your panels will never produce the 300W they produce in a lab, in reality a little over 250W is more or less the most you’ll get per panel, even in the height of summer.
I was predicting on a sunny winter’s day we would produce about 15kW, but the reality is half that. Worse, I also estimated the heat pump would use about 40kW on a cold day. This would probably be true if we set the thermostat where we used to have it for the gas boiler — we couldn’t heat more than we did, it would’ve cost a fortune. However, with the heat pump being so much more efficient and my wife liking a warm house, the heating is turned up considerably compared with how it was! Ultimately the heat pump uses more like 60kW, maybe even a little more, when temperatures are hovering around zero. They lose efficiency when the air temperature is colder and our house is a full 2 degrees centigrade warmer than it was before, all the time.
Clearly I’m still going to get a big electricity bill in winter!
That said, I will have virtually no electricity bill in the summer. As I said above, I’m going to have to change electricity contract and juggle with the heat pump settings so it does its storage heating in the middle of the day rather than at night, and other tweaks like this around the house — everything defaults to the idea electricity is cheaper at night, but that is no longer true when you have a PV array. But once all that’s in place, we’ll only use about 3kW from the grid at night for most of the summer, which is about 50p a day!
And with the virtual battery technology I mentioned last time, I can probably save about 250kWh when I’m away on my summer holidays (although not the 300kWh I stated, not bad either) which is still a few weeks of free heating in the autumn.
In terms of raw numbers, the electricity generated by our array over the last 6 months is worth about €200, though of course this is through the worst period of the year for solar power generation. We can probably generate a maximum of around 20kW a day a week either side of the summer solstice, so I’d say we’ll probably do a little better than €600 across the year. I can firm that up when I have a years-worth of data, of course, but we’ll have to wait 6 months for that.
We can extrapolate from that the solar panels — especially if you borrowed to buy them — will probably break even over 10 years rather than being any net gain. Which is fine, I’m confident we won’t lose money and every bit of carbon-neutral energy helps, so it was definitely worth it. And one mustn’t forget solar panels will continue to produce a decent amount of energy for you for a long time after the initial 10 year period I’m referring to in the calculations, so over their life you truly can expect them to save you over €10,000, if you consider the long game.
In short, don’t be too optimistic about your likely production, you’ll probably be disappointed, but that doesn’t mean it isn’t still worthwhile.
I promised more detail on operating the heat pump, so I’ll write that in the coming weeks and post it as a follow-up to “Part 2”.
