Earth Notes: KEHS talk: Our Solar PV System One Year On (2025)

[00:00]

[Alan] So we've now had our solar system installed - solar as in PV - on our roof.

[00:08]

We've got some actual numbers, which we didn't have a year ago.

[00:12]

And why did we do this? Well, we wanted to again reduce bills.

[00:19]

We could reduce our CO2 emissions and reduce our gas bill as well, both for water of course.

[00:29]

We thought it was worth a look. This is after we had that journey.

[00:33]

We went through that exercise of looking at all the things we could do on the house

[00:38]

and decided that solar PV was an easy win.

[00:41]

It was relatively inexpensive. It wasn't too disruptive to the house.

[00:46]

Bearing in mind that since we've bought the house we've put some engineering flooring down.

[00:51]

We've got carpets. It's decorated. Not saying it's perfection.

[00:55]

But if we were to do major works now we would be undoing all the good things we've already done.

[01:02]

I should add, prompted by Dan's talk, I said it was four hours to put solar panels in.

[01:08]

Yes it was, but the scaffolding had already been put up outside the house.

[01:12]

It wasn't four hours in total. But that was done as a separate activity.

[01:17]

So we thought "It's worth a look". We did exactly what Dan said.

[01:22]

We got about six quotes from relatively local-to-us installers in Kingston.

[01:30]

We used a mixture of word-of-mouth recommendation and I actually went to Which?

[01:38]

It happens I subscribe to Which?. I'm not so certain about some of its reviews.

[01:44]

But they've got a list of trusted traders.

[01:47]

We'd had some, I shouldn't be saying this, but we had one or two nasty experiences with Checkatrade

[01:54]

rated or qualified traders. So we weren't very happy with one or two of those.

[02:03]

We got our fingers burnt, not quite literally. Anyway, so yeah, a combination of both.

[02:11]

We got some quotes. Many of these companies will not visit your house. They'll give you a quote,

[02:16]

but they won't necessarily turn up at your property. They'll do it from using Google Earth and other facts

[02:24]

and just give you a number based on roof size. So be aware of that.

[02:30]

Our goal was with a budget. We actually did this unlike some installers, sorry, some installations.

[02:37]

Sorry I'm jumping around, but I've been triggered by a few of the comments.

[02:41]

We set ourselves a budget. We said "We're going to spend no more than this amount of money."

[02:46]

"What can we get?"  Where some people may do it the other way around.

[02:49]

I feel Dan's done it where he's wanted the best system he could have for his property.

[02:56]

Whereas we actually capped it up front. We said "We've only got this amount of money."

[03:01]

And then we went to these installers and said, "What sort of system can we get today with this sum?"

[03:09]

"How do we trade off the battery, number of other panels, how much energy will we get from that?"

[03:17]

And that's how we did this. As I already mentioned, we wanted a battery.

[03:22]

We thought that was going to be important, particularly for the winter months.

[03:25]

And we capture reduced energy costs electricity at night during the winter and fill our battery up.

[03:36]

Our battery's possibly a bit under-sized.

[03:39]

We also added electric water heating as a last minute feature, including a solar diverter.

[03:46]

We can talk about that in a moment. All these things I've been talking about with others.

[03:51]

Others have talked about ??? roof, slates, directions, structures.

[03:56]

We've now got a brilliant roof in so far as the amount of available south-facing roof space on our roof isn't great.

[04:04]

So we looked at this 20 years ago and everyone said, well, they're not worth doing.

[04:08]

But in the interim 20 years, panels have got much more efficient. They're much, much cheaper.

[04:16]

So it's a slightly different position today.

[04:21]

We've gone through the battery storing inside, outside. There's actually a specific regulation.

[04:28]

It's not a regulation, so it's not mandatory, as I would call it.

[04:33]

But there is a document that's referred here that actually gives guidance on where batteries are in home use of energy storage,

[04:44]

where they should go. So this is not complete.

[04:48]

So that's what we've got. That's what we've effectively got.

[04:52]

We've got 12 panels, 5 kilowatt peak capacity.

[04:57]

We've got a 9 kilowatt-hour battery and charger.

[05:04]

And actually, that's the point Damon mentioned.

[05:07]

You've got to be a bit careful - when we had our system put in place,

[05:11]

I said, say we want to run our washing machine and we want to run the kettle at the same time,

[05:17]

because there is a limit to what your inverter will enable.

[05:23]

And we went slightly upsized. We've got a 5 kilowatt capable device.

[05:31]

So we can provide, as we understand it, 5 kilowatts into the house from our battery.

[05:39]

If you don't look at that, you might find you can't do what I've just described.

[05:44]

You can't power two large appliances at the same time.

[05:48]

[Damon] You should be clear out there. That doesn't mean the lights will go out.

[05:51]

[Damon] It simply means you import a little bit from the grid.

[05:53]

[Alan] Yeah, it means you've got less of your own stored energy being used,

[05:57]

and more, as Damon rightly points out, more energy coming through your conventional electricity meter.

[06:04]

We've got this myenergi eddi power diverter, which feeds an old-fashioned cylinder in our case.

[06:13]

We haven't replaced our cylinder. We haven't replaced the immersion heater.

[06:18]

We can talk a tiny bit about that too.

[06:21]

But this is what the panels look like. That's a group of three panels on the front, south-facing.

[06:27]

And we've got another single panel on this face of the roof here.

[06:32]

And then we've got eight panels on the other face of our roof, total of 12.

[06:39]

Two separate pictures. Well, that's our rather busy consumer unit arranged with smart meter.

[06:47]

That's the smart meter. That's the fuse (isolator) for the solar components.

[06:58]

And in our garage by the door by the fire extinguisher in fact, we've got our battery pack,

[07:04]

which is a Fox made by company Fox. And then we've got the charger-inverter.

[07:10]

One unusual thing, relatively unusual, we've got per panel an inverter.

[07:17]

Typically, some PV systems have an inverter that takes what they call a string of panels,

[07:27]

and maybe an inverter will have two strings of six panels.

[07:32]

Because we've got our panels split across three roofs, we've actually got individual inverters on every panel.

[07:40]

That's the best you can have in today's technology.

[07:43]

It means that any shading or problem with an individual panel doesn't affect the other panel.

[07:51]

You can also look at the performance of the individual panels.

[07:56]

So it's quite good. You pay a little bit more for that.

[07:58]

You might ask how much more - I don't know precisely - but maybe a 10% hit, let's say, on price,

[08:05]

to have that individual panel inverter technology. But I think it's worth having.

[08:11]

Our battery is probably a bit undersized from what we've sort of gleaned during the year.

[08:17]

So it's rather small I'm afraid. In fact, I think if I just move on to the next, there's total here.

[08:25]

Some of you may be concerned about actual numbers in terms of saving, and there's a column on the right giving you some ideas.

[08:32]

But we've got to be very careful. In our one year of ownership, we've generated 4.3 megawatt-hours of electricity.

[08:41]

Now, we're probably running. We don't know precisely. Maybe I should know, but I don't know.

[08:48]

We're probably now down to about 5 megawatt [hours]. Those who heard my earlier talk.

[08:53]

We're probably using about 5 megawatt-hours of electricity a year if we didn't have solar.

[08:59]

But in spite of having solar, we've only used 2.8 megawatt-hours of the solar components.

[09:09]

We've actually got surplus that we were not able to use during the year.

[09:14]

So that extra 1.5 megawatt-hours, which is in the second line, that got exported back to our energy supplier Octopus.

[09:23]

Now, you don't get very much for that today. You only get about 15 pence per [kilowatt-hour]...

[09:29]

They're not, you know, maybe seems to be interested per se in that going back.

[09:34]

We would have been better off using it ourselves if we could.

[09:38]

But we were either not in the house when the sun was out and we were generating,

[09:44]

or we've not got a big enough battery such that we could capture some of that, or millions of variations, some of these.

[09:53]

We don't have an electric hob. So when we've got a frying pan on, we're not using that energy that we might have otherwise used.

[10:03]

So the other thing is our hot water regime, that use of our existing cylinder, old fashioned immersion heater,

[10:14]

we are not getting much energy into that by observation of the app that we've got for managing that.

[10:21]

What I'm saying is, if you want to heat your hot water using solar,

[10:26]

you probably need to install a new brand new super duper cylinder with optimised, you know,

[10:33]

element placement and so on. Even then, you're not going to make huge savings, but it would be more so.

[10:39]

So we've clearly saved some money. If you could use all of it, you could maybe save £1100 in actual bill terms.

[10:49]

But we didn't save £1100 because we didn't use all of it.

[10:53]

We could compute the amount of actually saved from the export.

[10:57]

But we've clearly saved money and used a large chunk of that solar energy that we've produced.

[11:03]

We've produced more than we thought we would, considering our slightly crazy roof shape.

[11:11]

So we think it's been quite good.

[11:15]

[APPLAUSE]