Solar PV - is it worth it?

wexfordman2

kceire wrote: »

20kwh would be rare enough.
FIT is the best option, I agree but it ain’t happen so we got to work with what we have.

I actually dont know what my daily use is, can I work it’s out by checking the meter figures?
I would only dump about 3-4kwh to the immersion on a good day Andy that gives me a full tank of hot water (300L new, highly insulated cylinder).

Also not sure on complete costing for a 4.3 system but my 3kw system including the immersion divertor cost me €2900 supplied and fitted while I was renovating my house last year. I didn’t do it for the financial gain, although it simply nice to save a little, I done it for the environment if I’m honest and to do my little bit as corny as it sounds.

Thats a decent price, I got a rough price today of 6k (after 3,800 grant) for a 4kw system with battery, so your 3kw system at 2,900 with no grant, compared to a price today of 10k for a 4kw system and battery,

Stark contrast, think I might shop around a bit more

listermint

Is anyone bringing in rising energy costs into their calculations. Already signs of problems with Russia and then talk of transportation from the states.

Surely the fluctuations have to come into cost accounts versus what a consistent fairly measurable figure obtained from pv

Gumbo

wexfordman2 wrote: »

Thats a decent price, I got a rough price today of 6k (after 3,800 grant) for a 4kw system with battery, so your 3kw system at 2,900 with no grant, compared to a price today of 10k for a 4kw system and battery,

Stark contrast, think I might shop around a bit more

Just for clarity, you won’t get that price offered by any company, now or even back then. It was a company I was working closely with at the time and it was a favor for a favor if you get me. It wasn’t realistic of the RRP at that time either.

I was getting quotes of 4kish for similar system from other company’s,

unkel

2,900 for that system is roughly the price of the parts incl. Vat if you get really good parts prices (most installers in Ireland would add at least 20% to that)

Install was pretty much free

kceire paid 2,900 for what Joe Bloggs keen on prices would have easily paid over 4,000 for. And other people even a lot more than that.

Shefwedfan

kceire wrote: »

Just for clarity, you won’t get that price offered by any company, now or even back then. It was a company I was working closely with at the time and it was a favor for a favor if you get me. It wasn’t realistic of the RRP at that time either.

I was getting quotes of 4kish for similar system from other company’s,

I was just going to say that.....you just paid for parts and labour with no mark up. Not many companies going to last selling at that price :P:P

Grumpypants

Trying to keep up with the thread. Are we saying a 2k panel with 2k battery would be about 4k installed? But the grant would make it closer to 2 - 2.5k?

At that price it's becoming an option. We live on a wonky power line and lose power for 3-6 hours about 10 times a year. And had been considering a back up generator. But if the battery would keep the freezer on and let us heat a baby bottle it would fill that job.

We already have the hot water solar tubes. In the summer that gets the water to about 40. Winter is never over 20. So we use a good bit of oil topping it up. So there is a chance to save both electricity and oil.

unkel

Shefwedfan wrote: »

I was just going to say that.....you just paid for parts and labour

Not even labour

Rough figures of prices incl VAT

10 * 300wp = 2000
immersion diverter = 350
inverter = 300
mounting materials and cables = 250

Total 2900

jt_dublin

Guys,
Not sure if the Home Renovation Incentive scheme has been mentioned before. If not... You can claim the VAT element back on works of €5000 and above, once the work is carried out by a "tax compliant contractor". So if you are a taxpayer, you can get 13.5% back over 2 years on your income tax. At the moment this scheme is only open until the end of 2018 but maybe it will be extended.

Has anyone availed of this?

H.E. Pennypacker

jt_dublin wrote: »

Guys,
Not sure if the Home Renovation Incentive scheme has been mentioned before. If not... You can claim the VAT element back on works of €5000 and above, once the work is carried out by a "tax compliant contractor". So if you are a taxpayer, you can get 13.5% back over 2 years on your income tax. At the moment this scheme is only open until the end of 2018 but maybe it will be extended.

Has anyone availed of this?

There’s a catch - the qualifying expenditure is reduced by three times the value of the grant. PV on its own is unlikely to qualify as the qualifying expenditure must be over €4,405 excluding vat. If combined with other qualifying works there would be some benefit

jt_dublin

H.E. Pennypacker wrote: »

There’s a catch - the qualifying expenditure is reduced by three times the value of the grant. PV on its own is unlikely to qualify as the qualifying expenditure must be over €4,405 excluding vat. If combined with other qualifying works there would be some benefit

Ok, I didn't realise that... Thanks for the info.

Water John

JT its still a good shout for anyone doing other works as well, thanks.

unkel

unkel wrote: »

Almost 10k for a 4kwp system plus 4.8kWh battery doesn't seem a good price at all tbh (7k after subsidy).

4kWp @ €1.20 p/w installed


4.8kWh battery = €500
Gubbins in middle = €800

unkel wrote: »

Li-Ion batteries last a lot longer than people thought they would.

People aren't pushing then to design limits is all. Look at lifetime energy extraction not calendar hours.

ArrBee

So, I posted this question in the PV grant thread but it was suggested that I should post it elsewhere.
I figure this is probably the most suitable....



If, over the year I average around 20kw per day and we had guaranteed 5hrs bright sun every day, then a 4kw array + battery would cover the daily needs, right?
Not counting spikes in demand that the PV setup didn't have capacity for. So assuming a constant demand from the house.

I know I've overly simplified the question, and that the size of battery + amount of power used outside of daylight hrs are huge factors.
But purely hypothetically to help me get my head around things.


So if my thinking is right, what would be a reasonable assumption for electricity yield in this country?
Would it be fair to say that you could expect to average 60% yield per daylight hr?

Whats with the batteries lads? Are we all so tight-fisted we can't allow the power enter the network.

A domestic battery might pay for itself over it's lifetime.

Look at the data!

5kWh is a camper battery.
less than 10kWh is a waste of time for a house.

Gumbo

Sir Liamalot wrote: »

Whats with the batteries lads? Are we all so tight-fisted we can't allow the power enter the network.

A domestic battery might pay for itself over it's lifetime.

Look at the data!

5kWh is a camper battery.
less than 10kWh is a waste of time for a house.

What’s the average daily consumption in kWh in Ireland?

10kWh p/d

Small batteries give diminishing returns.
Large battery, lower average discharge = exponential increase in lifetime energy.

Inverters are 80% efficient (real world figure) {EDIT: twice...double conversion for AC coupling}
Chargers are 80% efficient (real world figure)
Batteries are 80% to 95℅ efficient (real world figure).

Batteries are 150 years old, there have been no major improvements outside of maintenance schedule and energy density. This is not new tech.

Shefwedfan

Sir Liamalot wrote: »

10kWh p/d

Small batteries give diminishing returns.
Large battery, lower average discharge = exponential increase in lifetime energy.

Inverters are 80% efficient (real world figure)
Chargers are 80% efficient (real world figure)
Batteries are 80% to 95℅ efficient (real world figure).

Batteries are 150 years old, there have been no major improvements outside of maintenance schedule and energy density. This is not new tech.

So cheaper to pump back into netwrok?

Shefwedfan

Shefwedfan wrote: »

So cheaper to pump back into netwrok?

Cheaper to use it direct drive.
Greener to give it away, let the government sort out mechanical storage (unlikely).

No economy in wall art.

Alkers

Sir Liamalot wrote: »

Whats with the batteries lads?

Probably the €1k grant when getting an installation so you may as well include the smallest complying battery and include it to your installation for minimal cost?

niallers1

Sir Liamalot wrote: »

Whats with the batteries lads? Are we all so tight-fisted we can't allow the power enter the network

Yes

unkel

niallers1 wrote: »

Yes

Not something to be proud of imho. And you might re-consider if you knew that it probably costs you more to divert electricity than to give it away for free to the grid.

niallers1

I was joking.

Simona1986

Simona1986 wrote: »

Probably the €1k grant when getting an installation so you may as well include the smallest complying battery and include it to your installation for minimal cost?

€1k grant won't get you much in li-ion land.
I can do better cheaper without the grant.

unkel

Sir Liamalot wrote: »

€1k grant won't get you much in li-ion land.
I can do better cheaper without the grant.

2.4kWh li-ion battery is about €950 (ex VAT)

How much to install it though?

unkel

unkel wrote: »

2.4kWh li-ion battery is about €950 (ex VAT)

How much to install it though?

£300 including VAT for same in lead acid.
Open source ubiquitous hardware.

ArrBee

Sir Liamalot wrote: »

Whats with the batteries lads? Are we all so tight-fisted we can't allow the power enter the network.

A domestic battery might pay for itself over it's lifetime.

Look at the data!

5kWh is a camper battery.
less than 10kWh is a waste of time for a house.

Isn't a 5kwh battery going to supply 1kw for 5hrs?
Surely thats the purpose of it?

Like to use 5kwh less of grid power during non daylight hours....
or have I got it arseways?

Surely the idea of PV in the 1st instance is to take less from the grid and feeding into the grid for free only to buy electricity at a fluctuating market price goes against the idea?

Nope, the battery's internal resistance means the faster you discharge the less you get.
A 5kWh battery has 5kWh inside indeed.
Now is the manufacturer using over-zealous charge voltages like every portable device in production to get that figure reducing the overall battery life expectancy to one-sixth what it could be?

My phone has a li-ion cell rated 5.4Ah
It's end of charge voltage is 4.35V. This is detrimental to it's health.
At 80% charge it is 4.2V the standard end of charge voltage (and still 150mV too high).

So my phone has a 4.3Ah battery but the manufacturer plays with numbers and I have an over-clocked battery that has an operating envelope of 5.4Ah and a cycle life of 450 instead of 3000.

Back to the wall art quandry.
Beware Man Maths to follow.

Say you have a solar array with a 9 year payback. Say you only use a third on demand.
So 6 years of that payback depends on the battery system efficiency.
Let's accept the battery only pays for itself before it expires.

So of the 6 year storage payback
80% efficient Solar to Mains Bus to AC Couple
First conversion is free you were never going to get a 100% efficient inverter.

So you want to charge your battery with an 80% efficient charger. 7.5years payback.
But the battery is only 90% efficient. 8.3 year payback.
You want to use the energy in the battery? 80% efficient inverter. 10.4 year payback.

Plus original 3 year supply on demand time 13.4 year payback. Congratulations your battery added 50% expense to the lifetime of the system. But wait wasn't the system more expensive to install with the art complications.

So glad my taxes helped you. :rolleyes:

Datasheets are full of contrived optimised lab circumstances you'll never see in the real world. Look at your system power in versus power out then you'll understand.

gunnerfitzy

Would appreciate any thoughts on my battery conundrum:

Looking at getting approx 3kw solar array - I will get max 10 panels on my roof which is bang on south facing. Annual usage is approx 4200kWh. No electric showers. Energy efficient applicances, bulbs etc.

One installer is quoting approx €2k for 2.5kwh battery pack.

Grant without battery will be €1400. Grant with battery will be €3100. Difference of €1700. Based on this I can get a 2.5kwh battery for net price of €300 - no brainier me thinks. Total guesstimates here but if the battery was to save me €100 per year in usage costs then 3 years would have investment paid off. If the battery lasted 10 years then I would be up €700 from years 4 to 10.

The debate I am having with myself is whether or not to up the total battery capacity and get 5kwh battery system. This would require an additional investment of €2000 with a total investment of €2300. If I saved €200 a year in usage costs then I wouldn’t even recover my investment if the battery was to last 10 years.

I realise I am looking at this almost solely in monetary terms but in regards to the operation and mechanics of the battery, inverter, solar etc along with my usage are there other considerations I should be taking into account?

quentingargan

gunnerfitzy wrote: »

Would appreciate any thoughts on my battery conundrum:

Looking at getting approx 3kw solar array - I will get max 10 panels on my roof which is bang on south facing. Annual usage is approx 4200kWh. No electric showers. Energy efficient applicances, bulbs etc.

One installer is quoting approx €2k for 2.5kwh battery pack.

Grant without battery will be €1400. Grant with battery will be €3100. Difference of €1700. Based on this I can get a 2.5kwh battery for net price of €300 - no brainier me thinks. Total guesstimates here but if the battery was to save me €100 per year in usage costs then 3 years would have investment paid off. If the battery lasted 10 years then I would be up €700 from years 4 to 10.

The debate I am having with myself is whether or not to up the total battery capacity and get 5kwh battery system. This would require an additional investment of €2000 with a total investment of €2300. If I saved €200 a year in usage costs then I wouldn’t even recover my investment if the battery was to last 10 years.

I realise I am looking at this almost solely in monetary terms but in regards to the operation and mechanics of the battery, inverter, solar etc along with my usage are there other considerations I should be taking into account?

€2k per battery is quite high. I can see the first battery costing that as it needs a hybrid inverter, but second and subsequent batteries should be a lot less than that. Also, you have to find out what the USABLE power is. Most Li-Ion batteries can only be discharged to about 10% (50% for lead acid).

It all depends on usage. your payback will reduce if you don't use the full 5kwhrs each night, and in winter your system may not produce 5 kwhrs some days. On the plus side, remember that you will also be cycling your battery during the day. If your PV is producing 2kw and you switch on the washing machine at 3kw, the other 1kw will come from your battery instead of the grid. That may happen quite a bit at weekends and if the house is occupied during the day.

niallers1

Electricity costs tend to increase too so your sums are based in today's electricity price. If electricity costs go up payback would be sooner. .