PV Solar - Battery or not?

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Maesus114

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I've got 2 quotes for Solar panels and the first quoted for 10 panels with an immersion diverter at a cost of €9,100 before grant (€7,300 after) generating 3.95kWp.
He said I wouldn't need a battery as they only hold 50cent worth of electricity anyway.

2nd quote was for 12 panels 4kWp at a cost of €11,800 before grant, €8,800 after. This quote included battery and immersion diverter. This Company felt the battery was more important than the immersion switch.

2nd quote seems better but is who is correct? Also how long does a battery last. Are they like phone batteries that need replacing every 2 years?
 
If your primary goal is to maximise your financial return on your solar installation then neither the battery or the immersion diverter tend to make financial sense. The batteries are still quite expensive and do have a limited life. The diverter is also fairly expensive and will be offsetting probably gas which is quite cheap compared to electricity.

However when I put mine in my priorities were more like: reducing how much fossil fuel I use (being more green), the pure gadgetry/techiness of the thing, a backup power supply if the mains is offline, and then saving money at the bottom of the list (mega nerd, what can I say). If your priorities are more like mine then I'd definitely recommend the battery, it's great to see it covering all your nighttime usage and being able to run broadband/laptop during a power outage is handy. I'd probably go for the diverter again as well, having hot water all summer 'free of charge' is quite neat.

FWIW on my battery the warranty states that it will have at least 70% capacity after 10 years. So yes they do lose capacity, but nothing like a smartphone.

You should try to get as many panels on your roof as you can with the installation. The panels aren't super expensive, it's the getting somebody up there to install rails etc. that adds up. So while they're up there have them put up as many as possible. You'll over produce on summer days, but in the depths of winter a 4kW system will only produce a tiny fraction of that so the more panels the better! FWIW I put up 14 panels a couple of years ago, I could have fitted 18 and if I was doing it again today I would.
 
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I would agree with above. Maximize the panels.
If you decide to put more panels later or add to the system you might have to upgrade your inverter also.

I went with 8 panels and the inverter. No battery.

I am now looking at putting more panels up. I wish I had fronted up the extra at the time.

I now have to upgrade the inverter and potentially add battery
 
Leo said:
If that's really what an installer said, find yourself a new installer.
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Yeah that's not great! The number of cents the battery can hold isn't the figure you're interested in, it's the throughput over a time period that matters. That €0.50 could charge/discharge ten times a day and your saving would be €5 that day.

For reference I have a 5kWh battery in-place for 2 years now and the throughput has been about 4.5MWh. So the battery has helped me use an extra €450 of my generated solar (4500/2 * €0.20/kWh). The battery cost something like €3k after the grant, so it would take 13 years to break even at this rate.
 
The batteries are likely to make a lot more sense when the newer meters with different amounts for different times of the day come in. Think charging during the day and discharging at peak time.
 
You haven't hit break even at 13 years at that rate. You're ignoring the time value of money and the fact that after 13 years your battery will have depreciated hugely in value, perhaps even to nothing and may need replacing. (Although in fairness, electricity prices are only going one way so that's likely to increase your annual savings a bit too.) You need to look at what return you'd get from an alternative investment of 3k, maybe into a pension fund. If you're a high rate taxpayer, a pension contribution of 5k costs you 3k after tax. That should return a compound annual growth of 4% which is pretty close to your early years savings from your battery. But that's compounded. After 13 years, your pension investment has grown to well over 8k and is generating growth of 333 per annum. Your 13 year old batteries certainly won't be doing that.

It's easy to get sucked into the virtue of the thing and subconsciously exaggerate the savings. I love the idea of solar and "free" electricity from the sun. Plus it appeals to the engineer in me. But this is askaboutMONEY so the bottom line needs to be right too.

Panels probably meet the bottom line test now, and have dropped hugely in price over the last decade. Batteries need a far better price/performance ratio to be a good investment.
 
Thanks for all the replies. Sounds like getting a battery is probably better overall for night time use. Down the line we might have an electric car so than can take the excess generated when the battery starts to lose power.
 
Maesus114 said:
Thanks for all the replies. Sounds like getting a battery is probably better overall for night time use. Down the line we might have an electric car so than can take the excess generated when the battery starts to lose power.
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If you are going down the route of an electric car get them to wire for the charger when doing this as it needs to be connected to the same system as panels, inverter as well as the fuse board. They will be doing all that anyway for panels and inverter.

As far as I’m aware you won’t get grant for car charger unless you actually own the car or have proof of purchase.

Also be aware that when charging hybrid or electric cars that takes quite a lot of the energy that is generated by the panels which will affect the water heating.

If not enough power generated by panels they charge off the mains.

Therefore as suggested above go down the route of more panels now if that’s your plan for later
 
Those quotes aren't particularly good, there are alot of installers inflating costs at the moment so it's definitely worth shopping around.
A good rule of thumb I've seen on boards is 1k euro per 1kw installed, plus 500 euro per 1kw battery (after grant).
I've recently had installed a larger system, 21 panels (7.2kw) with 11 optimisers (due to shading), a 5kw battery, 6kw inverter and a hot water diverter, total 9650 after grant, generally though prices seem to be rising as the demand increases for components.

One other thing to note is that generally the system completely turns off if there is a power outage (generation and battery supply) this is to avoid electrocuting someone working on the mains, some batteries allow you to connect an 'extension' lead where you can plug in essential items during an outage, just don't expect it to supply the household mains.
 
Zenith63 said:
For reference I have a 5kWh battery in-place for 2 years now and the throughput has been about 4.5MWh. So the battery has helped me use an extra €450 of my generated solar (4500/2 * €0.20/kWh). The battery cost something like €3k after the grant, so it would take 13 years to break even at this rate.
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Can you not also use your battery to save money during the winter? Charge up at night at €0.05/kWh and use it during the day at €0.20/kWh?

Saving €0.15/kWh * 5 KWh per day = .75 per day or about 70 euro over the 3 winter months. Reducing your payback period to less than 6 years.
 
AJAM said:
Saving €0.15/kWh * 5 KWh per day = .75 per day or about 70 euro over the 3 winter months. Reducing your payback period to less than 6 years.
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You're assuming 100% efficiency in the charge / discharge cycle and inverter there!
 
Maesus114 said:
I've got 2 quotes for Solar panels and the first quoted for 10 panels with an immersion diverter at a cost of €9,100 before grant (€7,300 after) generating 3.95kWp.
He said I wouldn't need a battery as they only hold 50cent worth of electricity anyway.

2nd quote was for 12 panels 4kWp at a cost of €11,800 before grant, €8,800 after. This quote included battery and immersion diverter. This Company felt the battery was more important than the immersion switch.

2nd quote seems better but is who is correct? Also how long does a battery last. Are they like phone batteries that need replacing every 2 years?
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To go back to the OP's post:

Both of those quotes are poor value for money compared to what is available from the market with some shopping around. As mentioned there is an excellent long thread on boards.ie dealing with this and you will see how wildly the price varies from provider to provider.

Some batteries do have gaurantees given in a number of years, but many of them are actually for battery cycles - typically 5000. So you need to find out exactly which model of battery is being incldued and figure this into the calculation. 5,000 cycles of a 2.5kWh battery is only gauranteed for 12,500 units or about €2,500 worth of electricity at day rate. If you are charging the battery via night-rate or using the battery at night time, the value of this electricity drops significantly.

In my opinion it is madness to pay for a battery system now with the imminent announcement due of the feed in tarrif, where you will be paid for some of the excess electricity generated by panels. The detail of this could render batteries to be completely uneconomical. It is also not a big job to add a battery to a system at a latter date (new inverter is required).

If you're approaching this from a purely financial perspective, the quickest system to provide a return on investment will be the cheapest small system you can find with no battery and no diverter.
 
What is the max PV capacity / output you can install on a private house? Is there a limit? Thanks.
 
Dododo said:
What is the max PV capacity / output you can install on a private house? Is there a limit? Thanks.
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Any more than 12sqm of panels will require planning permission, but there is some precedents where people were allowed more. If it's the feed-in tariffs that interest you, the capacity of the inbound connection will limit output. The standard domestic supply is 12kVA here.
 
Leo said:
Any more than 12sqm of panels will require planning permission, but there is some precedents where people were allowed more. If it's the feed-in tariffs that interest you, the capacity of the inbound connection will limit output. The standard domestic supply is 12kVA here.
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Some additional info here: https://energyd.ie/solar-panels-and-planning-permission-in-ireland/

But the recent Bord Plenanla decision (details in the link) may have changed the ground rules.
 
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Thanks for that. Basically I was just wondering what was the max kw(h)s of PV I could install.
 
Leo said:
If it's the feed-in tariffs that interest you, the capacity of the inbound connection will limit output. The standard domestic supply is 12kVA here.
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That's an interesting constraint. I have a 16kVA connection, which was installed a decade ago on the advice of my Heat Pump installer. I don't really know whether it was needed or not, but decided to play safe!
Does that mean that because I have a larger capacity connection, I would be able to upload more to the national grid, when the time comes?
If so, would my potential increased upload capacity be in the region of 25% more than the standard connection, or is that too simplistic?
 
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