Solar panels and battery - any real world reccomendations?

[HungryHippos]

Does anyone run just a battery setup and pull down enough energy overnight when it's cheaper to use throughout the day?

We use around 9000kWh a year but the south facing part of our roof isn't big enough to get anywhere near the number of panels needed. I think we could fit 5-6 panels on the main roof and then 2-3 on the garage roof. The north facing part of the rooves could probably fit 15+ annoyingly!

We've discussed it a fair bit here, the main tariffs that support this are EV ones, if you don't have an EV but you wind up on one, there is a chance they could pull it out from under you. What I'm really getting it here, is you should design a system that doesn't just rely on that being the case.

You'd need a lot of battery power at 30kwh per day, which I think you'd potentially find it hard to charge up in the short off-peak tariff rates.

Not sure how fast you could charge at max speed, may depend on the number of batteries and max supply to the house.

9000 kwh is fairly high, have you looked at what is using that much power? that is around a constant 1kw all day long every day on average.

if you're looking at adding solar/battery/EV anyway you may as well consider contacting installers to see what they can do. South/North might in combination do a fair bit, though I think north is the worst for generation. A lot of solar farms are E/W to get flatter/longer generation even if S is better.

 

[OldKitMan]

Does anyone run just a battery setup and pull down enough energy overnight when it's cheaper to use throughout the day?

We use around 9000kWh a year but the south facing part of our roof isn't big enough to get anywhere near the number of panels needed. I think we could fit 5-6 panels on the main roof and then 2-3 on the garage roof. The north facing part of the rooves could probably fit 15+ annoyingly!

a 6 panel setup using 400w+ panels will still generate a tidy amount.

 

[upnorth]

My latest quote is:
10 x 8:33 400w panels
1 x GivEnergy 3.6kw Gen2 inverter
1 x GivEnergy 9.5kw/h battery
5 x Tigo optimisers
Bird protection
Al the other bits and bobs
£9,800

I don’t think that’s too bad but I can find very little info on the 8:33 panels - strange brand name.

 

[Hawk Tuah]

Do the Tigo's work 2 panels to an optimiser?

 

[HungryHippos]

My latest quote is:
10 x 8:33 400w panels
1 x GivEnergy 3.6kw Gen2 inverter
1 x GivEnergy 9.5kw/h battery
5 x Tigo optimisers
Bird protection
Al the other bits and bobs
£9,800

I don’t think that’s too bad but I can find very little info on the 8:33 panels - strange brand name.

Doesn't seem too bad to me at all.

 

[tsinc80697]

We've discussed it a fair bit here, the main tariffs that support this are EV ones, if you don't have an EV but you wind up on one, there is a chance they could pull it out from under you. What I'm really getting it here, is you should design a system that doesn't just rely on that being the case.

You'd need a lot of battery power at 30kwh per day, which I think you'd potentially find it hard to charge up in the short off-peak tariff rates.

Not sure how fast you could charge at max speed, may depend on the number of batteries and max supply to the house.

9000 kwh is fairly high, have you looked at what is using that much power? that is around a constant 1kw all day long every day on average.

if you're looking at adding solar/battery/EV anyway you may as well consider contacting installers to see what they can do. South/North might in combination do a fair bit, though I think north is the worst for generation. A lot of solar farms are E/W to get flatter/longer generation even if S is better.

Yes we have an EV, don't do many miles but we have one which helps for tariff requirements.

9000 is down from over 12000 last year. Realistically it's as low as it's going to get. We roughly use 800w 24/7 and it increases depending what we are using during the day/evening.

 

[upnorth]

Do the Tigo's work 2 panels to an optimiser?

Do the Tigo's work 2 panels to an optimiser?

No - you only need to put one on each of the panels likely to be affected by shade. In our instance, there are four panels shaded by a neighbour’s roof till about 9am and another one affected slightly by a chimney as the sun goes down very late in the afternoon. There not as sophisticated as Solar Edge which does require them on every panel.

 

[HungryHippos]

Yes we have an EV, don't do many miles but we have one which helps for tariff requirements.

9000 is down from over 12000 last year. Realistically it's as low as it's going to get. We roughly use 800w 24/7 and it increases depending what we are using during the day/evening.

Then you can get onto something like Octopus GO but you'll need a smart meter. That gives you 4 hours of cheap elec where you can charge the car up and stuff too.

With that done you may as well look at solar + battery, I think you'd struggle to fill 30kwh worth of batteries though in the 4 hour time window they give you without increasing supply to the house somehow.

A couple of 10~ kwh batteries might be good though, Givenergy make 9.5kwh batteries now. Add a few well placed solar panels and it would cut your bills a lot.

 

[Cadder]

320 kwh per month? about 10 per day if so, I'd budget around that level. Bigger system can be good but you want to pace it somewhere around what you may expect to use reasonably. Solar is more efficient when you use as much of the generation as you can.

Option 1 with a reasonable battery might be fair, but there is no scaffold cost there, not sure how much that adds. Givenergy do a 9.5kwh battery which may not cost tons more, worth finding out the difference maybe. Larger battery gives you more flexibility on usage times.

If the system isn't much above 3.6kw you can get away with a 3.6kw inverter and no need for a longer DNO application, can do the pre-approved one so potentially spun up quicker.

Try and make sure you get a hybrid inverter in case you want to add an EV later, I think hybrid makes it easier to add.

Yeah sorry - 320kWh per month is peak around December/January according to my Hugo app.
I asked the supplier and they say 9/10 times they can do everything from their tower which is included in price. They say scaffolding would be around £400 if necessary.

So option 1:

• 10 x JA Solar 405 or Canadian Solar 410W Mono solar panels
• 1 x Growatt 4kW Dual tracker inverter
• 10 x Schletter on-roof mounting kit (2 x 5 in portrait would need 5.6m width x 4m height)
• 1 x All cables, clips, generation meter, AC/DC isolators
• 1 x Installation & commissioning
• £4,595 inc VAT

Plus the following options:

• Battery installation charge - £200
• Two batteries from these options?:
  • 2 x GivEnergy 5.2kWh Lithium Ion Battery Storage System - £3,595 each
  • 2 x Fox 5.2kWh Lithium Ion battery Storage System - £3,495 each
  • 2 x SolaX 5.8kWh Lithium Ion battery Storage System - £3,895 each
• Zappi 7kW Tethered EV car charging station - £995
• iBoost / Solic200 Solar Immersion Controller - £295

That's looking like £13-£13.7k if I have assumed two batteries is the right way forward. Edit: removed

 

[tsinc80697]

Then you can get onto something like Octopus GO but you'll need a smart meter. That gives you 4 hours of cheap elec where you can charge the car up and stuff too.

With that done you may as well look at solar + battery, I think you'd struggle to fill 30kwh worth of batteries though in the 4 hour time window they give you without increasing supply to the house somehow.

A couple of 10~ kwh batteries might be good though, Givenergy make 9.5kwh batteries now. Add a few well placed solar panels and it would cut your bills a lot.

Thanks! We recently had a smart meter installed. Is there an average amount you can pull from the grid per hour or is it house dependant? I didn't think about whether there was a limit if we did fit 24kWh battery (for arguement sake) and tried to charge them to 100% over the 4 hour cheap period each night.

 

[upnorth]

That's looking like £13-£13.7k if I have assumed two batteries is the right way forward. I see no mention in my quote of an inverter so I assume this is additional cost.

Is the Growatt inverter not a hybrid one? See my quote above for the GivEnergy stuff in case it’s of any help to you. It works out a bit less but with a slightly lower capacity battery (9.5kw/)

 

[Hawk Tuah]

Thanks! We recently had a smart meter installed. Is there an average amount you can pull from the grid per hour or is it house dependant? I didn't think about whether there was a limit if we did fit 24kWh battery (for arguement sake) and tried to charge them to 100% over the 4 hour cheap period each night.

I think it's limited by your inverter and the battery charge rate.

 

[upnorth]

The thing that I find a bit frustrating that everybody tends to size the inverter to the array or just under. So a 10 panel 380-400kw array gets a 3.6kw inverter. But if you have a battery that can output say 5kw, you’re still stuck at 3.6kw because of the inverter this increasing the potential to top up from the grid when using high draw appliances. Some people have said that this method of sizing the inverter is out of date and there’s no reason why you couldn’t have an inverter with a higher rated output than the array so it can take advantage of the increased battery output. But I’ve seen nothing online which backs that up -everything says to match to the array or undersize the inverter. I appreciate there are G99 issues also.

 

[tsinc80697]

I think it's limited by your inverter and the battery charge rate.

Looks like Givenergy charge/discharge up to 3kw.


Quick bit of maths using our current eleectricity usage:
9000kwh @ 28p/kwh = £2520

Charging/discharging a 9.5kwh battery each day
3467kwh (9.5kwh battery filling every night) @ 7.5p/kwh = £260
+
5533kwh from the grid @ 28p/kwh = £1550

That's a saving of £710 per year.

Add in a 6x400w solar setup (producing 2000kwh per year?) would increase that to a saving of £1270 per year.

This could all be incorrect so please correct me if it is, but does that sound about right?

 

[Hawk Tuah]

The thing that I find a bit frustrating that everybody tends to size the inverter to the array or just under. So a 10 panel 380-400kw array gets a 3.6kw inverter. But if you have a battery that can output say 5kw, you’re still stuck at 3.6kw because of the inverter this increasing the potential to top up from the grid when using high draw appliances. Some people have said that this method of sizing the inverter is out of date and there’s no reason why you couldn’t have an inverter with a higher rated output than the array so it can take advantage of the increased battery output. But I’ve seen nothing online which backs that up -everything says to match to the array or undersize the inverter. I appreciate there are G99 issues also.

I'd have thought this is mostly so they keep the export amount to under 16a (so G98 only).

 

[HungryHippos]

Yeah sorry - 320kWh per month is peak around December/January according to my Hugo app.
I asked the supplier and they say 9/10 times they can do everything from their tower which is included in price. They say scaffolding would be around £400 if necessary.

So option 1:

• 10 x JA Solar 405 or Canadian Solar 410W Mono solar panels
• 1 x Growatt 4kW Dual tracker inverter
• 10 x Schletter on-roof mounting kit (2 x 5 in portrait would need 5.6m width x 4m height)
• 1 x All cables, clips, generation meter, AC/DC isolators
• 1 x Installation & commissioning
• £4,595 inc VAT

Plus the following options:

• Battery installation charge - £200
• Two batteries from these options?:
  • 2 x GivEnergy 5.2kWh Lithium Ion Battery Storage System - £3,595 each
  • 2 x Fox 5.2kWh Lithium Ion battery Storage System - £3,495 each
  • 2 x SolaX 5.8kWh Lithium Ion battery Storage System - £3,895 each
• Zappi 7kW Tethered EV car charging station - £995
• iBoost / Solic200 Solar Immersion Controller - £295

That's looking like £13-£13.7k if I have assumed two batteries is the right way forward. Edit: removed

I'd ask them about the 9.5kwh battery they do, it may be cheaper than 2 x 5kwh batteries. One less thing to go wrong as well.

 

[upnorth]

I'd have thought this is mostly so they keep the export amount to under 16a (so G98 only).

Possibly - which is what I alluded to at the end. But if people are happy to go down the G99 route, it seems there’s no point in doing so due to the inverter size issue.

 

[HungryHippos]

Looks like Givenergy charge/discharge up to 3kw.


Quick bit of maths using our current eleectricity usage:
9000kwh @ 28p/kwh = £2520

Charging/discharging a 9.5kwh battery each day
3467kwh (9.5kwh battery filling every night) @ 7.5p/kwh = £260
+
5533kwh from the grid @ 28p/kwh = £1550

That's a saving of £710 per year.

Add in a 6x400w solar setup (producing 2000kwh per year?) would increase that to a saving of £1270 per year.

This could all be incorrect so please correct me if it is, but does that sound about right?

Yes, so in your shoes it could be worth doubling on the battery to get nearer 20kwh worth, solar will top up and lower grid draw.

Remember unit rates are likely to go up more soon, probably even on the Go one for peak, so worth using as many cheap (off-peak) and free (solar) ones as you can.

 

[Harnser]

if you're looking at adding solar/battery/EV anyway you may as well consider contacting installers to see what they can do. South/North might in combination do a fair bit, though I think north is the worst for generation. A lot of solar farms are E/W to get flatter/longer generation even if S is better.

Thought I saw a comment in the thread about winter generation and east/west but can't see it now so replying to this one. I'd need E/W orientation as my big roof is north facing and the south one broken up by gables. Looking at the generation data on https://twitter.com/edent_solar (scroll down to see the winter figures) it does look lower than I'd expect from a south facing array of the same size. Anyone more knowledgeable able to comment? Array details at https://shkspr.mobi/blog/2020/04/comparing-solar-panel-generation/.

 

[tsinc80697]

Yes, so in your shoes it could be worth doubling on the battery to get nearer 20kwh worth, solar will top up and lower grid draw.

Remember unit rates are likely to go up more soon, probably even on the Go one for peak, so worth using as many cheap (off-peak) and free (solar) ones as you can.

Is it worth considering adding panels on NEE and NNW facing parts of the roof or is the drop off significant when not using south facing?

The panels don't seem to be an expensive part of the cost (from what I can tell), so adding 5x400w for ~£1000 (plus additional install cost I assume?) on a NEE/NNW facing roof would save some money per year, but is it worth it on that direction roof.