Help with solar pv

[Mike_scotland]

Me and my partner are building our own home and were considering installing solar panels, can someone tell me a 5kw system would that produce 5kw of energy an hour or is that a day or?

 

Were based in east of scotland so its sunny/light enough but unsure how it all works.

 

With the rising costs of electricity im considering a 5kw system and battery.

 

Thoughts?

 

Thanks in advance.

 

Mike

[ProDave]

No, 5kW is the maximum instantaneous power it would generate at mid day on a sunny day.  In summer it would typically generate in the region of 20kWh per day, and not much in mid winter.

 

You would probably get about 4000kWh per year.

[SteamyTea]

kW is power

kWh is energy

 

 

[Nickfromwales]

MCS says you will get around 25% max during the winter, so with a 5kWp you will really not be able to consider a battery as you'll be able to chafge it for free for only a few months of the year and it'll have around a 10-12 year useful life. 

Get your monies worth via 'free' hot water, which with a hot water cylinder and an immersion heater should be around 6+ months of the year.

 

[Mike_scotland]

4 hours ago, Nickfromwales said:

MCS says you will get around 25% max during the winter, so with a 5kWp you will really not be able to consider a battery as you'll be able to chafge it for free for only a few months of the year and it'll have around a 10-12 year useful life. 

Get your monies worth via 'free' hot water, which with a hot water cylinder and an immersion heater should be around 6+ months of the year.

 

Are you recommending the solar thermal?

[pdf27]

2 hours ago, Mike_scotland said:

Are you recommending the solar thermal?

Nope - various companies sell a widget which measures how much electricity you're exporting to the grid and feeds it into the immersion heater instead. They were developed back when we had a feed-in tariff and didn't meter exports - you were just deemed to be using 50% of what you generated, so anything extra used on site rather than exported was free.

 

How valuable this is nowadays depends a lot on who your electricity supplier is - most will only pay 0.1p/kWh for exported power, but Octopus are currently paying 5.5p/kWh fixed export rate and much higher on the variable rate (probably temporarily).

Since 5.5p/kWh is more than the cost of gas, then assuming you go for an MCS installation then it **may** be worth exporting to the grid rather than feeding to an immersion heater.

 

It's worth noting that an MCS installation adds cost and is only required if you wish to be paid for export. @ProDave can give you chapter and verse on this since he didn't go down the MCS route for his installation and as a result exports virtually nothing.

[Mike_scotland]

do you still get money if you pay into the grid? i thought that was cancelled?

[joth]

7 minutes ago, Mike_scotland said:

do you still get money if you pay into the grid? i thought that was cancelled?

 

Yes it's called the Smart Export Guarantee now, much lower rates, see league table below. 

You need an MCS certified install  to qualify for payments.

 

https://www.solarguide.co.uk/smart-export-guarantee-comparison#/

Edited September 27, 2021 by joth

[Mike_scotland]

thanks Joth.

the feeling im getting is solar panels are likely not worth it now especially in Scotland?

[ProDave]

4 minutes ago, Mike_scotland said:

thanks Joth.

the feeling im getting is solar panels are likely not worth it now especially in Scotland?

I would say not worth it if you pay full price for am MCS install.  But I installed mine myself and they will have paid for themself in saved electricity in less than 6 years.  You only need a competent electrician to install them.  for a new build I would say definitely worth it for lower bills and the few extra SAP points you get.

[Mike_scotland]

1 minute ago, ProDave said:

I would say not worth it if you pay full price for am MCS install.  But I installed mine myself and they will have paid for themself in saved electricity in less than 6 years.  You only need a competent electrician to install them.  for a new build I would say definitely worth it for lower bills and the few extra SAP points you get.

i think i was quoted 4k for a 4kw system is that mcs prices? or what should i be looking for if i get a good spark to fit them?

[ProDave]

1 minute ago, Mike_scotland said:

i think i was quoted 4k for a 4kw system is that mcs prices? or what should i be looking for if i get a good spark to fit them?

Mine cost £1500 for the parts.  A days labour to fit, add another £250

[AliG]

I have a 5kw system in Scotland.

 

It should cover its costs, a battery is still not a great deal.

 

If you can use half the electricity you generate and get paid 5p per kWh for the other half (or use it to heat water instead of gas), then you are looking at £500 a year in savings at 20p a kWh.

 

£4k ish installed is about right, so even at this price you would have a decent return, clearly much better if you can DIY a system.

[Mike_scotland]

5 minutes ago, AliG said:

I have a 5kw system in Scotland.

 

It should cover its costs, a battery is still not a great deal.

 

If you can use half the electricity you generate and get paid 5p per kWh for the other half (or use it to heat water instead of gas), then you are looking at £500 a year in savings at 20p a kWh.

 

£4k ish installed is about right, so even at this price you would have a decent return, clearly much better if you can DIY a system.

yeah thats what im thinking, so basically i was just trying to work out how much energy would be made during each day/month, i know that depends on cloud cover/weather but it would be interesting to know an average,

[joth]

8 minutes ago, Mike_scotland said:

yeah thats what im thinking, so basically i was just trying to work out how much energy would be made during each day/month, i know that depends on cloud cover/weather but it would be interesting to know an average,

Have you put your details into PVGIS?

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

 

 

[Mike_scotland]

6 minutes ago, joth said:

Have you put your details into PVGIS?

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

 

 

that looks a tad too hard for me to use mate lol. have you used it ?

[SteamyTea]

38 minutes ago, Mike_scotland said:

so basically i was just trying to work out how much energy would be made during each day/month

Something like this?

 

You can get it all from PVGIS

[A_L]

32 minutes ago, Mike_scotland said:

that looks a tad too hard for me to use mate lol. have you used it ?

 

Its easy, just select your location and follow your nose! For Forfar it gives about 890kWh/yr per kWp with about 4kWh/day per kWp in summer and about 0.7kWh per day per kWp in Jan/Dec

Edited September 27, 2021 by A_L
typo

[Mike_scotland]

2 minutes ago, A_L said:

 

Its easy, just select your location and follow your nose! For Forfar it gives about 890kWH/yr per kWp with about 4kWh/day per kWp in summer and about 0.7kWh per day per kWp in Jan/Dec

 

so for the installed peak power is that how many kw system i will have?

[A_L]

2 minutes ago, Mike_scotland said:

so for the installed peak power is that how many kw system i will have?

 

Yes.

[Mike_scotland]

im typing in Tealing were i am based with a 4kw system 14% loss i think its telling me roughly 3600kwh/year does that sound about right?

so if im getting 3600 kwh x 0.19p per kwh from the grid that would be £684 returns a year so it would take roughly 6 years to break even?

[SteamyTea]

3 minutes ago, Mike_scotland said:

im typing in Tealing were i am based with a 4kw system 14% loss i think its telling me roughly 3600kwh/year does that sound about right?

so if im getting 3600 kwh x 0.19p per kwh from the grid that would be £684 returns a year so it would take roughly 6 years to break even?

Sounds about right.

 

But remember that is energy, the kWh, not power, that will be a lot lower most of the time.

[Mike_scotland]

1 minute ago, SteamyTea said:

Sounds about right.

 

But remember that is energy, the kWh, not power, that will be a lot lower most of the time.

so you dont think i would get the 3600 kwh free to run electrical items in my house? as an example if my heating was electric and 3600kwh would it not be totally free?

[SteamyTea]

6 minutes ago, Mike_scotland said:

so you dont think i would get the 3600 kwh free to run electrical items in my house? as an example if my heating was electric and 3600kwh would it not be totally free?

You would have to match the load to the generation.

The trouble is the generation is constantly varying, your load, while it is on, is constant.

So sometimes, your generation may be producing 2 kW, and your load is only 1 kW, the difference leaks out though the wires to the grid.

If it is the other way around 1 kW generation and 2 kW load, then all the generation will go to the load, plus the extra 1 kW will be drawn from the grid.

This is why people use diverters.  They try and match the load to the grid.  But if your load is greater than the maximum generation at any time, then it will draw from the gird.

And in the summer, when your load is low, most of your generation will be exported.

 

Edited September 27, 2021 by SteamyTea

[Mike_scotland]

2 minutes ago, SteamyTea said:

You would have to match the load to the generation.

The trouble is the generation is constantly varying, your load, while it is on, is constant.

So sometimes, your generation may be producing 2 kW, and your load is only 1 kW, the difference leaks out though the wires to the grid.

If it is the other way around 1 kW generation and 2 kW load, then all the generation will go to the load, plus the extra 1 kW will be drawn from the grid.

This is why people use diverters.  They try and match the load to the grid.  But if your load is greater than the maximum generation at any time, then it will draw from the gird.

And in the summer, when your load is low, most of your generation will be exported.

 

 

 

awwwww i get you now, its such a hard decision, part of me wants to buy a battery and charge it at night with cheap elecy from octopus go (4p)