Solar PV (7.5kW) + Battery (15kWh) Costs

Mr_Clark1000

Hi All,

So, haven't posted on here for a while. We managed to whittle down our debts through spending control, pay rises and re-mortgaging, managed to get on a very good deal at the time just before interest rates went up which allowed us to get rid of our Credit Card debts (never using those again!).

So we found ourselves with about £14,000 to either do the following with:
1 - Clear our remaining fixed loans, which we pay around £200 a month for, have about 4.5 years left for that.
2 - Spend money on improving house

Whilst the original plan was just clear out all our debts and keep within our means, with the massively rising cost of energy, we have re evaluated our options.

We use quite a lot of energy at home, with an electric car and family of 4, often hosting gatherings for family as well, so we use around 7,200 kWh for the house and around 2,300 kWh on car. That's obviously quite a bit so the incoming price rises are pretty bad.

I have some experience of solar having installed a small array on our garage roof years ago, so I am keen.

Looking at the sums, if we were to leverage a battery system with solar, and charge car / fill batteries on Octopus Go tariff, we could probably get away with running the house fully off the 15kWh battery during the day and have the car fully charged on that rate as well. This makes it incredibly attractive, even ignoring the fact that from around April - October, we could most likely run the house via solar alone.

So far I have one quote and it works out to £15,865. Lead time is quite long and looking at November install. It seems all installers are rammed now (wonder why).

Breakdown is as follows:

- 19 * JA solar 395watt Panels, 7.5kW Peak, including mounting rails, DC cabling, scaffolding, Installation, comissioning.

- Solis RHI-6K-48ES-5G Hybrid Inverter

- FOX ESS LV5200 5.12kWh Battery Sub-Total for this base system is £11k Additionals we want: - Additional 10kWh of battery (2*FOX ESS Units, £1500 each): £3000 - Automatic Changeover Switch to run essential circuits off grid (we get frequent power cuts here so would be beneficial): £600 - New Distro Board (current one is 20+ years old): £750 - Anti-Bird guards around all solar panels: £400 So grand total is £15,800 for install, registration, off grid mode, 7.5kW of solar and 15kWh of battery. Really, it would be good to hear what peoples thoughts are on the above.  I've done sums all day and it seems that payback is looking at 5 - 8 years depending on how silly these prices get. Seems like a worthwhile investment in our house and energy future? Thanks for any info or thoughts!

Solarchaser

I would say this, generally solar is viewed as a good deal with 1w = £1
As solar installers have become busier that number has increased in most (but not all) cases to more like 1w = £1.20
So 7kw £8.4k

Batteries are harder to do as their cost has increased also, but maybe 2.5kwh = £1k

So for 15kwh maybe £6k

So in short I'd say that's a pretty good deal.

Payback is hard to be accurate,  as it very much depends on you. 

In summer you will buy very little. 
Add in a zappi car charger and you will benefit from free car charging when it's sunny too.

In winter with 15kwh of batteries you will still buy quite a bit at higher rate as your usage of electricity is higher than 15kwh, in winter, but you will also be highly likely to use all the battery every day.

Worth checking the dod on the batteries and also the round trip efficiency of the inverter, generally 80% for both is a good standard if you can't find figures.


If you want to really drill down you would have to look at your month by month bills vs historical data of solar irradiation,  that will give you figures of what you will get for free (solar charging) vs what you will have ro pay for (cheap rate charging).

Anyway, very short answer, I think that looks a decent deal especially with all of your extras. 

QrizB

Mr_Clark1000 said:

Breakdown is as follows:

- 19 * JA solar 395watt Panels, 7.5kW Peak, including mounting rails, DC cabling, scaffolding, Installation, comissioning.

- Solis RHI-6K-48ES-5G Hybrid Inverter

- FOX ESS LV5200 5.12kWh Battery Sub-Total for this base system is £11k Additionals we want: - Additional 10kWh of battery (2*FOX ESS Units, £1500 each): £3000 - Automatic Changeover Switch to run essential circuits off grid (we get frequent power cuts here so would be beneficial): £600 - New Distro Board (current one is 20+ years old): £750 - Anti-Bird guards around all solar panels: £400 So grand total is £15,800 for install, registration, off grid mode, 7.5kW of solar and 15kWh of battery.

That seems a pretty good price, helped by the exceptionally keen pricing of those Fox batteries (£300/kWh isn't a price point we see very often, especially this year).

I don't know if you're anywhere near @Harry1986 but his best quote has a similar bottom line to yours but for a somewhat smaller system. He might be interested to compare with this.

ccbrowning

That's cheaper than any quote I've gotten, and mine only included 9.5kW of battery and less PV.

ABrass

Yep, that's a good price, I got a quote for £14k for 8kW and 13kwh inc bird netting and backup power connection. No new Consumer Unit though.

Screwdriva

I struggled with this one. On one hand, I'm a big fan of paying off loans to avoid all interest payments. On the other, energy is so expensive right now that it would make sense to minimize its inflationary effect on your household. 

I just can't get behind such a large battery bank. If you were to delete it, and leverage the incredibly attractive Octopus Outgoing Agile SEG tariff to export your solar, effectively making the grid your "battery", you'd save alot of £ upfront, which you could put to better use. Yes, you wouldn't have the mental satisfaction of knowing that you're using your own energy at night but the net result will likely be the same, if not better, for the foreseeable. 

Here's a snapshot of the export tariff paid where I live. Just something to think about unless the power cuts are a deal breaker.

70sbudgie

I'm starting to wonder if you work for Octopus @Screwdriva !

Screwdriva

70sbudgie said:

I'm starting to wonder if you work for Octopus @Screwdriva !

I've been told I co-own a rooftop solar installation company and now that I'm an Octopus employee. All in a week of suggestions. What next, I'm Kwasi Kwarteng?

70sbudgie

Well, you constantly going on about Octopus agile was one of the prompts that led me to finally sort out my switch to outgoing agile. Which is causing me much excitement this week.

So I, for one, can't complain!

Screwdriva

70sbudgie said:

Well, you constantly going on about Octopus agile was one of the prompts that led me to finally sort out my switch to outgoing agile. Which is causing me much excitement this week.

So I, for one, can't complain!

I just took a look and can see why. Glad my banging on about this helped

- Kwasi

Mr_Clark1000

Thanks for all the replies guys, good to know I have a pretty competitive quote. Only concern now is getting it booked in and stock availability.