We had these seven solar panels installed in early July on the part of our roof that is south-facing. The panels and their battery are working well and we spend quite a lot of time looking at an app that tells us how much solar electricity we are generating and the state of play of the battery which stores excess solar energy.
Here’s what it looked like early-ish yesterday morning:
The panels weren’t producing any power (it was still almost dark!) but we weren’t using any from the grid either. Since 7pm the evening before, when solar generation ceased, with a low sun in a cloudy sky, the house ran on solar electricity generated the previous day and stored in and then released from the battery which was still 37% full (that’s 63% empty for pessimists). A dribble of solar started again around 7am which slowed the rate of battery depletion which bottomed out at 20% around 8:30am and then battery began to fill again as solar generation exceeded our power use, even though it was a cloudy, slightly drizzly, morning.
Around 1pm (midday GMT and therefore potentially peak sun for the day) things looked like this:
The battery is charging and is half full (and half empty).
By 7pm the battery has reached 100% (at c5pm) and the solar generation is dropping and so it’s a mixture of solar and discharging the supply from the battery which is powering the house:
Yesterday, and most days recently, even cloudy ones, our home electricity use is 58% the solar being generated in real time and 41% the solar stored in the battery, leaving less than 1% coming from the grid. And we have used 94% of the solar generated on the roof and exported 5% to the National Grid (at the moment for free!) – on clear sunny days the export figure is much higher.
Of course, those solar panels and the battery and the scaffolding and the team of guys to fit them all cost money – >£9000 in fact but that included the cost of removing broken very old solar water-heating panels which had to be removed some time and our roof is not that easy to get at so the scaffolding costs might be higher than other houses. Also, there was the opportunity to get some work done on roof slates and tiles while the scaffolding was up so there was an element of two birds with one expensive stone.
Payback time will be something like five years but much less if we eventually get an electric car, and there may be a slight uplift in the sale price of the house if the solar panels have a proven track record of delivering free energy.
There is also a feeling of smugness that one is doing something green – and that is priceless, of course.
Further updates will follow – particularly if snags emerge!
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Your August 25 Newsblast claims circa £40 per month saving in electricity. As it is July that your panels were installed you have been getting the best solar generation possible. Assuming that saving continues over the year then the annual saving is £480. Not to be sniffed at but:
for a capital outlay of £9000 the return on capital is unlikely for circa 18 years, not the 5 year payback you claim in your article.
How did you do your sums?
Martin – thanks. I’m glad you are thinking about the sums.
First – this last bill, I’m pretty sure, includes some time (not very much, but some) when the panels weren’t installed so the £40 is a minimum.
Second – we were away for quite a lot of July (compared with last July and a normal July) so the savings were lower than they otherwise would have been. The real savings are what we would have spent this year under normal circumstances I guess.
Third – I haven’t looked up the price of electricity last July and now so it’s an interesting illustrative figure rather than an absolute nailed down figure (and I didn’t say that the payback period was based on it but I would have raised an eyebrow myself, just as you did, if I had been reading this).
Fourth – when choosing a tariff without solar panels you have to balance the cost of electricity that you use with the daily standing charge that you have to pay anyway. As you can see, the less electricity you pay for from the grid, the higher proportion of your total bill is the standing charge, so it would make sense to switch to a different supplier with a lower standing charge (and increase your saving). I think it would be fair to include that in the savings as it is not possible to be realised without the switch to solar.
Fifth – similarly, by judicious timing of electricity use one should be able to push more of one’s use of energy to ‘free now you’ve paid for the panels’ electricity and off-peak prices (depending on who you sign up with) so that even in winter you can make further savings compared with previous winters.
Sixth – our electricity use in summer is low anyway – you can only save what you use but later in the year, maybe September?, electricity use will be higher and the solar may make a smaller percentage difference to electricity bills but a higher actual difference. Seems likely, but we’ll have to wait and see. Obviously, 100% saving of a £40 bill is less than a 70% saving of a £80 bill (figures for illustrative and explanatory purposes only).
Seventh – we aren’t earning any money from excess solar yet. That will make a difference too. Today is a cloudy day but now, after 6pm, our battery is full (99%) and the incoming solar is meeting half of the current electricity use of the house. Today, 43% of our solar generation has gone into the grid and I haven’t been paid for it. There’s no need to thank me for this donation.
Eighth – the overall price includes a hefty sum (but I couldn’t do it myself!) for removing the duff old panels we had. You’ll have to excuse me not telling you all the financial ins and outs of what we paid but anyone who wasn’t an early adopter about 25? years ago wouldn’t have that element of the bill to pay and it’s not really a cost of solar panels (except it is a cost of a bad decision back in the day).
Ninth – the cost of scaffolding was quoted separately from the cost of removing the old panels and is a sizeable chunk. Now, there are three things we needed to do at some stage (and were planning to do) which involved scaffolding: remove the old panels, install new panels and get some work done on replacing slates, pointing tiles and bricks etc. If we had done those three things separately we would have paid three times so is it reasonable to discount the cost of the solar installation because it directly produced savings elsewhere? I think so, but I didn’t actually do so.
Having solar panels changes the way you look at your electricity use. Just as some people with high (day) and low (night) tariffs adjust when they turn on the dishwasher etc having solar makes one think in a similar way with a third option. It is possible (though I don’t have a clue how at the moment) to top up the battery with low-tariff grid electricity and then sell back to the grid at high-tariff rates in the day. That’s quite cool. But already we would be likely to have showers at times when we wouldn’t be using grid electricity and when we wouldn’t take the top off the battery level. In time, almost certainly within five years, we’ll have to replace our car. Even now, when our daughter comes to stay with her electric car then it will be cheaper for us now than before, to plug it in to our socket! If you produce your own electricity then the cost of running an electric car comes down even more – though the capital outlay is large compared with any car I’ve ever bought – but that is potentially for the future.
Most of this is revenue, lets turn to capital. If the £9k had remained in the bank then it would have earned interest but it might not have remained in the bank it might have been spent on all sorts of things from grandchildren to an electric car to better bottles of wine. How does one cost that? And when we move from this house, unless it is 15 years hence (which I doubt for several reasons) the house will have solar panels installed with a guarantee on them. How does one cost that?
And it’s not all about money though it does cost money. Lower fossil fuel use is a public good – my grandchildren will benefit from it more than I and more than their parents. How does ne cost that?
But, if you Martin, or anyone else has got this far, not much of the above went into the comment on a five-year payback time. That figure is commonly used by the industry and I don’t know whether it is right but the limited ground-truthing I’ve done with others and thinking through some of the elements mentioned above, suggest it must be about right. Our energy use is relatively low so it may take a longer period to pay back (if that’s all you are interested in – which I’m not). Also, if electricity prices plummet then it will take longer but if they mount than it will take less time.
We’re only six weeks in, so there is a lot to learn, and I’ll share some of it on blogs and through my monthly newsblast.
Thanks Mark
The financial payback is, as you suggest, just one factor. The environmental impact is probably more important.
A bit late to comment, but we had solar panels this year too – 12 and a battery. Couldn’t be more pleased with them and since April we have been almost self-sufficient. The only reason I say “almost” is because the battery output can’t power the power shower alone, so needs some from the grid or direct solar – which costs only a few pence a day.
It would be better to have had a battery which works in a power cut, so we could be completely independent when necessary. But the only such battery offered was a Tesla – so we declined. I guess we could add a non-Tesla battery sometime and increase our storage, but not sure if we could mix types like this.
All in all, the panels have far exceeded our expectations, and the battery hasn’t gone below 35%. Will be interesting to see how it goes in winter.
Enjoy the app – I do!
Forgot the bit about the gadget that heats the water in the immersion tank! Once the battery is full, the solar power then switches to heating the water. If we need hot water before this, we can simply press the switch and it uses battery power to heat it up. “Free” hot water since April!
Also, all this bought through the council group buying scheme.
I highly recommend such a system!