Solar Panels UK - is it worth it?

[GarethWhyte]

Hello,

I'm wondering if you guys can help, I've read most of this post and to be frank its at the limit of my understanding.

A colleague has given me some advice around Solar but I would like to pick your brains and get the groups help if I may. The current situation is:

• Just come of a very cheap rate 10p per KW Hour and now on Octopus Go paying 37.35 (I think!) during the day and 12p between 00:30 - 04:30
• We are an electric only house in a new build property 4 Bedroom Detached (Built December 2021) with an Air Source Heat pump.
• Just my wife and I using the washing machine once a week and not allowed the dishwasher on or tumble drier.
• Using approximately 8500 KW per year including charging for my Model 3
• Work from home 2/3 days a week

My colleagues advise is to go relatively low on panels perhaps 4.5/5 KW but go high on batteries 12kw or so. The plan would be to run the house of the panels during the day and anything over current use go into the batteries and charge the car during the 'off peak' rate. Ideally I would like to be as close to self sufficient as possible and don't see a major benefit in selling back.

I would welcome peoples thoughts about what sort of system/batterys would work and if it's practical. My ideal budget would be £12,000/£15,000.

If anyone knows of any great companies please feel free to recommend.

Thanks for reading a long post and for any help received.

Gareth

 

[RedMod3]

Hello,

I'm wondering if you guys can help, I've read most of this post and to be frank its at the limit of my understanding.

A colleague has given me some advice around Solar but I would like to pick your brains and get the groups help if I may. The current situation is:

• Just come of a very cheap rate 10p per KW Hour and now on Octopus Go paying 37.35 (I think!) during the day and 12p between 00:30 - 04:30
• We are an electric only house in a new build property 4 Bedroom Detached (Built December 2021) with an Air Source Heat pump.
• Just my wife and I using the washing machine once a week and not allowed the dishwasher on or tumble drier.
• Using approximately 8500 KW per year including charging for my Model 3
• Work from home 2/3 days a week

My colleagues advise is to go relatively low on panels perhaps 4.5/5 KW but go high on batteries 12kw or so. The plan would be to run the house of the panels during the day and anything over current use go into the batteries and charge the car during the 'off peak' rate. Ideally I would like to be as close to self sufficient as possible and don't see a major benefit in selling back.

I would welcome peoples thoughts about what sort of system/batterys would work and if it's practical. My ideal budget would be £12,000/£15,000.

If anyone knows of any great companies please feel free to recommend.

Thanks for reading a long post and for any help received.

Gareth

We are all electric with air-sourced heat pumps. I think you have to model your energy consumption against numbers of batteries and the solar kWh per month, and see what suits your particular case. We are high energy users and will have 9kW net solar and 3 Tesla PWs eventually; they match with our particular circumstances. We are all different. I am on Octopus GO and will renew in March.

 

[RedMod3]

Oh and for those who didn’t believe my earlier post on power cuts, I’m sure they’ll be coming. But those with PWs should be ok, I know I will be.

 

[spon88]

Hello,

I'm wondering if you guys can help, I've read most of this post and to be frank its at the limit of my understanding.

A colleague has given me some advice around Solar but I would like to pick your brains and get the groups help if I may. The current situation is:

• Just come of a very cheap rate 10p per KW Hour and now on Octopus Go paying 37.35 (I think!) during the day and 12p between 00:30 - 04:30
• We are an electric only house in a new build property 4 Bedroom Detached (Built December 2021) with an Air Source Heat pump.
• Just my wife and I using the washing machine once a week and not allowed the dishwasher on or tumble drier.
• Using approximately 8500 KW per year including charging for my Model 3
• Work from home 2/3 days a week

My colleagues advise is to go relatively low on panels perhaps 4.5/5 KW but go high on batteries 12kw or so. The plan would be to run the house of the panels during the day and anything over current use go into the batteries and charge the car during the 'off peak' rate. Ideally I would like to be as close to self sufficient as possible and don't see a major benefit in selling back.

I would welcome peoples thoughts about what sort of system/batterys would work and if it's practical. My ideal budget would be £12,000/£15,000.

If anyone knows of any great companies please feel free to recommend.

Thanks for reading a long post and for any help received.

Gareth

A key question is which way does your roof point and do you have any shading? South facing will produce most but East/West is viable and give you around 85% of South facing overall.

To give a marker, we have 5.1 kwp on our east and west facing roofs - 10.2 kwp total gave us 11kwh today, sunny spells and quite bright. I expect that to easily triple in summer.

In general it's recommended to put as many panels on your roof as possible.

We have 19 kWh of storage which we charge from solar and Octopus Go Faster (now defunct). With ASHP you will need plenty of storage, 12kwh is likely not enough - but a good start.

We paid 16.5k for our system before the mad rush, but now I would expect well over 20k. I'd tend to prioritise panels given that you only want scaffold up once. You can always extend your battery capacity later as budget allows.

You may be in for a wait as the industry is mad at the moment. Also lots of cowboys going back into it. Good luck with it and post your specs back so we can take a look.

 

[ACarneiro]

Oh and for those who didn’t believe my earlier post on power cuts, I’m sure they’ll be coming. But those with PWs should be ok, I know I will be.

View attachment 901142

Just trying to squeeze the last few little bits of panic out of the masses, eh?

 

[DaveNN]

Hello,

I'm wondering if you guys can help, I've read most of this post and to be frank its at the limit of my understanding.

A colleague has given me some advice around Solar but I would like to pick your brains and get the groups help if I may. The current situation is:

• Just come of a very cheap rate 10p per KW Hour and now on Octopus Go paying 37.35 (I think!) during the day and 12p between 00:30 - 04:30
• We are an electric only house in a new build property 4 Bedroom Detached (Built December 2021) with an Air Source Heat pump.
• Just my wife and I using the washing machine once a week and not allowed the dishwasher on or tumble drier.
• Using approximately 8500 KW per year including charging for my Model 3
• Work from home 2/3 days a week

My colleagues advise is to go relatively low on panels perhaps 4.5/5 KW but go high on batteries 12kw or so. The plan would be to run the house of the panels during the day and anything over current use go into the batteries and charge the car during the 'off peak' rate. Ideally I would like to be as close to self sufficient as possible and don't see a major benefit in selling back.

I would welcome peoples thoughts about what sort of system/batterys would work and if it's practical. My ideal budget would be £12,000/£15,000.

If anyone knows of any great companies please feel free to recommend.

Thanks for reading a long post and for any help received.

Gareth

I'm just about to install 4.05kw of PV ( due south roof), after running with 3 x 3000 pylontech batteries ( giving about 9kwhr with the dod set at 90%) with a Sofar inverter.
Total hardware cost, Inc a new consumer unit about £8.5k.
Additional labour + mcs etc about £1k.
I agree with your mate on sizing....it's a trade off.
We charge the batteries overnight at 10ppkwr, they take us easily through the the early evening at worst.
We use the big appliances , Inc the dryer at night.
Smoke alarms etc in situ...but will swap out for a heatpump dryer.
I'd suggest doing the solar pv first..get your certs and add the batteries after.....I couldn't, sadly.

As noted above, you might benefit from extra PV .
But I'm limited to roof space.
I reckon on a 7 Yr ROI...with the batteries being better.
I plan to move home in about 7yrs...I might take the lot out and install in the next home.

 

[DaveNN]

Oh and for those who didn’t believe my earlier post on power cuts, I’m sure they’ll be coming. But those with PWs should be ok, I know I will be.

View attachment 901142

EPS set up.
Auto change relay to be wired in...but might simply run an extension cable to the lounge for the TV and one to the boiler.

 

[WannabeOwner]

go relatively low on panels perhaps 4.5/5 KW but go high on batteries

Sizing to what you use would be best, but that apart I would recommend fitting as many panels as you can - the cost of Scaffolding / "coming out to do the job" and inverter overheads etc are static, but the cost of additional panels is very modest.

Your Heat Pump is going to use Electricity in Winter ... and your PV is going to generate the best part of Nought

So battery, charged Off Peak, sized to support Heat Pump during a winter's day would also mean that battery was on the large size, and in Summer would store enough to power the house from sun-down to dawn in the Summer. Thus PV that will generate 100% of what you use in Summer, and a battery that will contain that would be my suggestion for minimum PV.

Make sure the battery is not too big to fully charge in a 4-hour Off Peak slot ...

South facing will produce most but East/West is viable and give you around 85% of South facing overall.

East/West gives you twice as much roof area as someone with a North/South roof ... so although the South will generate more, at peak, the East/West will generate more overall, it will also start earlier / finish later so a shorter "night" for the Battery to have to cover. Also for folk out-to-work East / West is more likely to be generating Morning / Evening when they are still at home.

10.2 kwp total gave us 11kwh today, sunny spells and quite bright. I expect that to easily triple in summer.

Should be more than triple Mid Summer should be close to 10x the mid Winter generation ... we are a bit past mid-Winter now, so perhaps 7~8 times what you would get now

P.S. If your house is well insulated - you'd hope so for a 20221 build, but building regs don't require much (compared to e.g. Passive House) - you could also set Thermostat a degree high during the night to encourage the Heat Pump to run during that time

 

[Mrklaw]

I'd be interested to see maths on a HP battery. In theory it makes sense - maybe you have an 8-10kwh for your baseload and during summer that'll be constantly topped up with PV so only has to cover a portion of your daily load. But for HP thats heavily winter when solar is least generating. May only just cover your baseload.

But how many days will it be needed, and what is the saving? You'll be off-peak shifting most of the time so its peak-off peak as your saving. Although maybe offset by total kwh used over the season?

Would be curious to see how that calculates out

 

[DaveNN]

Sizing to what you use would be best, but that apart I would recommend fitting as many panels as you can - the cost of Scaffolding / "coming out to do the job" and inverter overheads etc are static, but the cost of additional panels is very modest.

Your Heat Pump is going to use Electricity in Winter ... and your PV is going to generate the best part of Nought

So battery, charged Off Peak, sized to support Heat Pump during a winter's day would also mean that battery was on the large size, and in Summer would store enough to power the house from sun-down to dawn in the Summer. Thus PV that will generate 100% of what you use in Summer, and a battery that will contain that would be my suggestion for minimum PV.

Make sure the battery is not too big to fully charge in a 4-hour Off Peak slot ...



East/West gives you twice as much roof area as someone with a North/South roof ... so although the South will generate more, at peak, the East/West will generate more overall, it will also start earlier / finish later so a shorter "night" for the Battery to have to cover. Also for folk out-to-work East / West is more likely to be generating Morning / Evening when they are still at home.



Should be more than triple Mid Summer should be close to 10x the mid Winter generation ... we are a bit past mid-Winter now, so perhaps 7~8 times what you would get now

P.S. If your house is well insulated - you'd hope so for a 20221 build, but building regs don't require much (compared to e.g. Passive House) - you could also set Thermostat a degree high during the night to encourage the Heat Pump to run during that time

Some good experienced knowledge here.

 

[DaveNN]

I'd be interested to see maths on a HP battery. In theory it makes sense - maybe you have an 8-10kwh for your baseload and during summer that'll be constantly topped up with PV so only has to cover a portion of your daily load. But for HP thats heavily winter when solar is least generating. May only just cover your baseload.

But how many days will it be needed, and what is the saving? You'll be off-peak shifting most of the time so its peak-off peak as your saving. Although maybe offset by total kwh used over the season?

Would be curious to see how that calculates out

I'm going down the thermal store route when I throw my hp in ( got to be unlooped first)
This is often frowned upon but as I have access to very cost effective kit, it makes sense to me.

 

[ringi]

Make sure the battery is not too big to fully charge in a 4-hour Off Peak slot ...

So a Powerwal is not a good option as it can't be fully charged in 4 hours.

Yet another reason to want V2H as charging rates with a DC link to a EV are so much higher then a home battery.

 

[scdoubleu]

So a Powerwal is not a good option as it can't be fully charged in 4 hours.

Yes it can. I've charged mine from flat to 100% during the 4 hour window, pulling 3.7 kW. It does take pretty much the entire 4 hours though.

 

[spon88]

Sizing to what you use would be best, but that apart I would recommend fitting as many panels as you can - the cost of Scaffolding / "coming out to do the job" and inverter overheads etc are static, but the cost of additional panels is very modest.

Your Heat Pump is going to use Electricity in Winter ... and your PV is going to generate the best part of Nought

So battery, charged Off Peak, sized to support Heat Pump during a winter's day would also mean that battery was on the large size, and in Summer would store enough to power the house from sun-down to dawn in the Summer. Thus PV that will generate 100% of what you use in Summer, and a battery that will contain that would be my suggestion for minimum PV.

Make sure the battery is not too big to fully charge in a 4-hour Off Peak slot ...



East/West gives you twice as much roof area as someone with a North/South roof ... so although the South will generate more, at peak, the East/West will generate more overall, it will also start earlier / finish later so a shorter "night" for the Battery to have to cover. Also for folk out-to-work East / West is more likely to be generating Morning / Evening when they are still at home.



Should be more than triple Mid Summer should be close to 10x the mid Winter generation ... we are a bit past mid-Winter now, so perhaps 7~8 times what you would get now

P.S. If your house is well insulated - you'd hope so for a 20221 build, but building regs don't require much (compared to e.g. Passive House) - you could also set Thermostat a degree high during the night to encourage the Heat Pump to run during that time

Agreed on the roof area, perhaps what I should have said is that purely based on unit area, south facing always wins. The longer generation time and more roof area for E/W is certainly an advantage in some respects though.

You're spot on with the 7-8 times - I just checked with one of the main solar databases and I was pleasantly surprised to see that at peak generation (July) we should have rather a large excess! We'll need to use the car more - it was worth the extra panels though as the incremental cost for those is relatively small in the overall scheme. I've certainly been impressed with the performance of the panels so far, even on relatively dull days.

 

[Mrklaw]

Agreed on the roof area, perhaps what I should have said is that purely based on unit area, south facing always wins. The longer generation time and more roof area for E/W is certainly an advantage in some respects though.

You're spot on with the 7-8 times - I just checked with one of the main solar databases and I was pleasantly surprised to see that at peak generation (July) we should have rather a large excess! We'll need to use the car more - it was worth the extra panels though as the incremental cost for those is relatively small in the overall scheme. I've certainly been impressed with the performance of the panels so far, even on relatively dull days.

But if you have an E/W roof aren't you likely to have more area than solely a south facing roof (assuming same house footprint)? So does the question then become does an E/W roof beat a N/S roof? Probably still yes. I'm fitting panels on the north as we don't have much space so even at 50% capacity of the south panels (and mainly 6 months of the year) it'll still generate useful baseload and helps us save a little bit off the battery install costs

 

[RagingWhisky]

Yes it can. I've charged mine from flat to 100% during the 4 hour window, pulling 3.7 kW. It does take pretty much the entire 4 hours though.

Second that!

In this case its all about what the inverter can suck from the grid!

Got two inverters, feeding 37.5kwh of battery storage + 9kwh on the sunamp at night.
- 4 hour octopus go window, and can see the draw on the grid hitting anywhere from 15-18,000watts at the peak

 

[SimonV]

I'm just about to install 4.05kw of PV ( due south roof), after running with 3 x 3000 pylontech batteries ( giving about 9kwhr with the dod set at 90%) with a Sofar inverter.
Total hardware cost, Inc a new consumer unit about £8.5k.
Additional labour + mcs etc about £1k.
I agree with your mate on sizing....it's a trade off.
We charge the batteries overnight at 10ppkwr, they take us easily through the the early evening at worst.
We use the big appliances , Inc the dryer at night.
Smoke alarms etc in situ...but will swap out for a heatpump dryer.
I'd suggest doing the solar pv first..get your certs and add the batteries after.....I couldn't, sadly.

As noted above, you might benefit from extra PV .
But I'm limited to roof space.
I reckon on a 7 Yr ROI...with the batteries being better.
I plan to move home in about 7yrs...I might take the lot out and install in the next home.

That seems very cheap at 8.5-9k. I had a quote of £13 for less than 4kw and only 5kw battery. Who are you using?

 

[DaveNN]

That seems very cheap at 8.5-9k. I had a quote of £13 for less than 4kw and only 5kw battery. Who are you using?

Trade Sparky for my Sofar Battery Inverter
HDM for my batteries
Solar Energy Stores for panels etc and Solar inverter.

 

[MrT3]

But if you have an E/W roof aren't you likely to have more area than solely a south facing roof (assuming same house footprint)? So does the question then become does an E/W roof beat a N/S roof? Probably still yes. I'm fitting panels on the north as we don't have much space so even at 50% capacity of the south panels (and mainly 6 months of the year) it'll still generate useful baseload and helps us save a little bit off the battery install costs

Go too big and you could run into DNO approval problems depending on where you live, proximity to substation and how many other people have solar installations.

 

[spon88]

But if you have an E/W roof aren't you likely to have more area than solely a south facing roof (assuming same house footprint)? So does the question then become does an E/W roof beat a N/S roof? Probably still yes. I'm fitting panels on the north as we don't have much space so even at 50% capacity of the south panels (and mainly 6 months of the year) it'll still generate useful baseload and helps us save a little bit off the battery install costs

I see what you are saying. What I mean is per unit area of installed panels, south wins by a fair degree. So even though we've got 10.2 kwp split E/W, our generation was still less than folk with say half that with fully south facing on some of the recent sunny days. That's if believe some of the figures posted on other forums. But then we're not seeing the full benefit at all yet due to the sun's arc and elevation. It's improving all the time and by end March I think we'll be covering most of our daily usage. E/W will be very handy in a few months with a much longer generation day.

I'm glad we put as much on the roof as possible - we'll be OTT come summer but at the moment we're still getting quite decent generation even on average winter days. We're only a couple of months in and still learning, but it's fascinating stuff and very satisfying!