Worth installing PV on entirely West facing roof

[Huckleberrys]

Hello.  Title says it'll really. I am doing a barm conversion and only have the west facing roof to play with. I can fit 4Kw of panels on there...is it worth it?

[Conor]

Model it through PV GIS https://joint-research-centre.ec.europa.eu/pvgis-photovoltaic-geographical-information-system_en

[Huckleberrys]

I did last night actually and got about 3500 Kwh per year which I thought was OK...that's where this forum comes in and my knowledge ends...is that worth it? It will be on a holiday let so I don't imagine the yearly usage would be that much so may benefit from a battery and an EV charger for myself! 

[Russdl]

DIY or MCS fit?

 

4 minutes ago, Huckleberrys said:

It will be on a holiday let so I don't imagine the yearly usage would be that much

That probably answers your question. It won’t be worth it. 

[Huckleberrys]

It would be DIY fitted. 

 

Although initially a holiday let I would probably move in there one day.

[Conor]

24 minutes ago, Huckleberrys said:

I did last night actually and got about 3500 Kwh per year which I thought was OK...that's where this forum comes in and my knowledge ends...is that worth it? It will be on a holiday let so I don't imagine the yearly usage would be that much so may benefit from a battery and an EV charger for myself! 

That's good. Mine gets 4.5mWh per year for a similar system with about 50% south facing. So far this year since april we've save £380 on imports, so yours could well be worth it. Will mostly depend on if you can make use of it, and if you have an EV and a Zappi charger, should be good.

[joth]

Before going DIY bear in mind Octopus Outgoing is now offering 15p/kWh for exports and who knows this could increasing again over the lifetime of the panels, and you'll only get that payment if you go MCS install.

 

The old rule of thumb is 50% of annual generation is exported which would be £260 of payments per year. Obviously some on here manage to self use far more than 50% and if you get a battery the calculus shifts again.

 

In terms of the original question, 3500kWh per year from 4kW of panel is a good yield, we only get about that on our SW roof due to tree shading. 

 

Edited September 22, 2022 by joth

[JohnMo]

If it for a holiday let, why put such a big array on the roof.  Put 1kW or so on the roof, then most would be self consumed, with no effort and not worry about export.

[Dillsue]

As a holiday let is it part of your property and on the same supply as your house, or on a separate supply?

 

Our original 4kw system was modelled at 3400kwh/year and has done 3500-3700kwh/year since 2015

[Huckleberrys]

It's a completely separate supply. I already have 4kw on an East West roof on my supply!

[Dillsue]

19 minutes ago, Huckleberrys said:

It's a completely separate supply. I already have 4kw on an East West roof on my supply!

Whether its worth it is entirely up to you then. Depends on how much, if any, ROI you want, when your gonna move in, how easy to charge your EV etc etc

[JohnMo]

Put it on that roof, but route the power to your house?

[Ferdinand]

I think TBH this depends on your definition of "worth it".

 

Are you motivated by ROI payback, or by using less energy / reducing emissions, or by have a local power resource that limits your dependency on the grid whilst still hvaing it available as a top up?

 

Depending on your answer to that question, lots of answers are possible.

[RichardL]

Go for it - I'm 4kW array on a WSW roof -  it means we only generate decent amounts around lunchtime but right into the evening.

In June-Aug when you get the long evenings to 8-9pm its generating and offsetting house load all the time.
 

Peak I have seen is around 3.6kW from the 4kW array - usually its more like 2.5 with clean sun.

That charged the battery to 90% yesterday and even now is offsetting the house daily base load of around 500W
Not enough to divert to the immersion heater since last month though.

Don't expect any miracles re getting the max theoretical output from the panels.

Think of it more like an investment in the building - roof/windows etc -

(My opinion only) All this 'pays for itself' stuff is a little odd -  gas and oil boilers never pay for themselves - indeed they consume even more money after install to run!

[Radian]

2 hours ago, RichardL said:

(My opinion only) All this 'pays for itself' stuff is a little odd -  gas and oil boilers never pay for themselves - indeed they consume even more money after install to run!

 

This is what I like about people sharing their opinions here. I'm always open to adoption 😃

Reminds me of when @SteamyTea mentioned how good value for money power actually was when compared to employing manual labour on minimum wage! (or words to that effect)

 

 

[SteamyTea]

34 minutes ago, Radian said:

 

This is what I like about people sharing their opinions here. I'm always open to adoption 😃

Reminds me of when @SteamyTea mentioned how good value for money power actually was when compared to employing manual labour on minimum wage! (or words to that effect)

 

 

Too right.

I am not going to push a car a mile for 50p.

A human needs around 2 kWh a day, that is a a fifth of a litre of diesel (ish, would not matter if it was a quarter). My local Tesco is charging £1.80 for a litre. So 2 kWh is 30p (and some clubcard points).

The best value for calories food that is easily available is lentils, my local Tesco sells a kg of them for £1.80.

They have around 4 kWh of energy in a kg bag (about the same energy content as timber or other biomasses).

So to get 2 kWh cost 90p, 3 times as much as pump diesel.

That is before processing costs i.e. boiling.

To cook half a bag will take take around 10 minutes boiling (for the split red ones).

On my induction hob that will be around 0.1 kWh of electricity, or 3p (ish).

Washing up about the same. So close to 4 times the price of pump diesel.

Now my favourite curry is, just by chance, a dhansac, a lentil based dish. For £8 I get about a half kilo of it.

OK, it has some ghee, very high energy content, and some meat, also high, and a lot of flavour. But I can get all the ingredients for less than a £1 (I can if I want also spend £10 on ingredients at the artisan shops, but it tastes the same and I have to wash the dirt off).

So as tonight is my night off, I am going to fill the car up, get a curry and tomorrow, fart the lentils out in a satisfying manner.

Ok, probably going to cost me 90 quid in all today, once I add in a drink and a packet of fags.

But at least I know what terrific value filling my car up (the major cost, I will drive it about 450 miles next week) is compared to the rest (except the fags, they are calories free).

Edited September 25, 2022 by SteamyTea

[Johnnyt]

We have 3 arrays over 2 strings totalling 10.02kWp

 

WSW array of 4.08kWp has generated thus far 3.396mWh (832Wh per kWp)

ENE array of 2.04kwp has generated 1.38mWh (676Wh per kWp)

SSE array of 3.9kWp has generated 3.3 mWh (846Wh per kWp)

 

They are all optimised with minimal shading.

 

In conclusion, west looks good.

[Adsibob]

On 25/09/2022 at 10:23, SteamyTea said:

They have around 4 kWh of energy in a kg bag (about the same energy content as timber or other biomasses).

Not raw they don’t. Well maybe to a bomb calorimeter they would, but I doubt you’d be able to digest them raw. What’s the net figure after allowing for your cooking energy consumption (per portion, in that I assume you don’t cook a 1kg bath all at once).

Edited September 26, 2022 by Adsibob

[SteamyTea]

9 hours ago, Adsibob said:

What’s the net figure after allowing for your cooking energy consumption (per portion, in that I assume you don’t cook a 1kg bath all at once).

 

On 25/09/2022 at 10:23, SteamyTea said:

So to get 2 kWh cost 90p, 3 times as much as pump diesel.

That is before processing costs i.e. boiling.

To cook half a bag will take take around 10 minutes boiling (for the split red ones).

On my induction hob that will be around 0.1 kWh of electricity, or 3p (ish).

Washing up about the same. So close to 4 times the price of pump diesel.

Now my favourite curry is, just by chance, a dhansac, a lentil based dish. For £8 I get about a half kilo of it.

OK, it has some ghee, very high energy content, and some meat, also high, and a lot of flavour. But I can get all the ingredients for less than a £1 (I can if I want also spend £10 on ingredients at the artisan shops, but it tastes the same and I have to wash the dirt off).

 

[Adsibob]

9 hours ago, SteamyTea said:

I can get all the ingredients for less than a £1 (I can if I want also spend £10 on ingredients at the artisan shops, but it tastes the same and I have to wash the dirt off).

Have you looked into the differences in health between grass fed meat and non-grass fed? Certainly with beef, there are significant health benefits of buying grass fed; something to do with the ratio of harmful fats to healthy fats. Also affects the ratio of fats in  butter and ghee. Irish butter is usually made from dairy milk that comes from grass fed cows are there is plenty of grease in Ireland. Not sure how you would go about finding the equivalent for ghee. Worth spending money on. Irish butter isn’t even that much more expensive. Grass fed beef does cost a lot more though.

[SteamyTea]

16 minutes ago, Adsibob said:

Have you looked into the differences in health between grass fed meat and non-grass fed

No specifically.

Read up on organic vegetables, they have no nutritional benefits at all.

 

Just to be controversial, if all meat was factory farmed in sheds, on preprocessed fodder, meats would be a lot cheaper. 

Then buyers could decide if they wanted to buy a product raised in that manner.

I assume they would not want it, so that would free up a lot of land resources for other uses.

Kind of veganism via the back door.

 

Normal milk has all the fat removed at the dairy, then put back in at 1, 2 or 4% by volume.

How they keep the quality so good.

Edited September 27, 2022 by SteamyTea

[Adsibob]

15 minutes ago, SteamyTea said:

Read up on organic vegetables, they have no nutritional benefits at all.

I thought the jury was still out on this.

 

15 minutes ago, SteamyTea said:

Just to be controversial, if all meat was factory farmed in sheds, on preprocessed fodder, meats would be a lot cheaper. 

Then buyers could decide if they wanted to buy a product raised in that manner.

I assume they would not want it, so that would free up a lot of land resources for other uses.

Controversial indeed. But a lot of meat is produced in that way and people still buy it. Ultimately, a lot of people can't afford to eat free range. The mad cow disease scandal was caused by farmers having to cut corners to be able to sell beef cheap enough to sell. A better solution in my view (also controversial) would be to ban all farming practises which are dangerous/risky. I've read a lot about diet (e.g. book by Tim Spector) and in my view he reliably shows that the healthiest diet is pescatarian, but with red meat thrown in once every 10-14 days or so. Something to do with it being very difficult/almost impossible for most people to absorb certain B vitamins from anything other than a bloody steak, but only needing that vitamin a couple of times a month.

Edited September 27, 2022 by Adsibob

[SteamyTea]

2 minutes ago, Adsibob said:

thought the jury was still out on this

No, been known for decades. It is one of those zombie statistics that refuses to die.

[Adsibob]

27 minutes ago, SteamyTea said:

No, been known for decades. It is one of those zombie statistics that refuses to die.

I thought it was more nuanced at least. For example, root vegetables that are organic are healthier, but they are the only ones where the differences are noticeable, because they are in constant contact with the soil. So chemical free soil impacts them more.

[SteamyTea]

1 hour ago, Adsibob said:

I thought it was more nuanced at least. For example, root vegetables that are organic are healthier, but they are the only ones where the differences are noticeable, because they are in constant contact with the soil. So chemical free soil impacts them more.

Getting rather off topic this is.

 

The main problem is comparing like for like