Solar Panels UK - is it worth it?

[Simavon]

We are glad we went for approval for fully covering both roofs (roughly W and E - not quite, we get more output from the W facing roof). It less than doubles the cost of the system, but we get twice the output and we can use a lot of it.

However, if we add a Powerwall now, we will be restricted to 3.6kW on that. That will limit its ability to supply peak demand in the winter evenings.

 

[PITA]

We are glad we went for approval for fully covering both roofs (roughly W and E - not quite, we get more output from the W facing roof). It less than doubles the cost of the system, but we get twice the output and we can use a lot of it.

However, if we add a Powerwall now, we will be restricted to 3.6kW on that. That will limit its ability to supply peak demand in the winter evenings.

If the Powerwall is restricted to discharge at 3.6kW... that's still ok though, isn't it?

At least the majority of your home demands are covered, and a very decent 13.5kWh capacity.

With a Gateway 2, you'd be able to island from grid blackouts and use Solar on top of that...

Better than losing all your power if grid fails

 

[Battpower]

Those talking to sales guys ...

Check out G100. It is a relatively recently standard I believe for export and may be import control.

On the basis that standards like G98 and G99 and their predecessors are pretty tight on their specs (IE: they are expected to work and devices are certified for compliance), if G100 can ensure zero export (which imo is what you want unless you have a deal that will pay you at least as much for export as you pay for import) then I'm not sure what grounds a DNO has for limiting the PV panel capacity. All the panels do are take load off the grid. Charging batteries from the grid is a different issue, but presumably the more your panels generate, the less you need to import as long as you have somewhere to usefully dump all the energy generated even at peak output / lowest local consumption.

As others have commented, it does seem wasteful though to have raging hot water mid summer just to avoid export. Having export capped at the old 3.6kw g83 limit wouldn't seem to much of a problem.

 

[Battpower]

We are glad we went for approval for fully covering both roofs (roughly W and E - not quite, we get more output from the W facing roof). It less than doubles the cost of the system, but we get twice the output and we can use a lot of it.

However, if we add a Powerwall now, we will be restricted to 3.6kW on that. That will limit its ability to supply peak demand in the winter evenings.

My aspect is pretty much South. May be SSW, with no exposure on North. Having an easterly aspect is especially useful if you have drained batteries with overnight use. The sooner you start generating in the morning, the sooner you stop importing... In many cases you only need 300 - 500 watts for background loads.

If you can charge batteries overnight (the sense of which absolutely depends on their being a decent night / day price difference) then less important, but eventually - may be sooner than later - low rate tariffs need to end as we will have much increased demand and hopefully more network buffer storage.

 

[Yachtsman]

This is what I love...

Right now I'm sat in the living room, in January, with our Heat Pump heating on. It's 22.5 degrees toasty... and 5 degrees outside.

Our Solar Array is producing 1.3kW of power... but our house demand is only 1.9kW... with 600W being supplimented from our Powerwall storage batteries (filled with cheap overnight electric at 5p).

No 'peak rate' Grid...

It really is a good setup.

View attachment 760384

Pita, you sound extremely smug & I don’t blame you, hopefully I’ll be feeling the same soon.

 

[RedMod3]

To qualify that, the 5% VAT rate is only where the materials are less than 60% of the total amount. For a PowerWall (or similar large capacity battery) it is highly unlikely that there are enough installation/labour costs to make up 40%.


Source: Tax on shopping and services

However, if the householder is over 60, the Powerwall and PV Panels will be charged at 5% VAT irrespective of the labour materials split. Not all installers know this.

Energy-saving materials and heating equipment (VAT Notice 708/6)

How to account for VAT if you’re a contractor or subcontractor installing energy-saving materials and grant-funded heating equipment.

www.gov.uk

 

[Battpower]

However, if the householder is over 60, the Powerwall and PV Panels will be charged at 5% VAT irrespective of the labour materials split. Not all installers know this.

Energy-saving materials and heating equipment (VAT Notice 708/6)

How to account for VAT if you’re a contractor or subcontractor installing energy-saving materials and grant-funded heating equipment.

www.gov.uk

These rules are so complex that you can't help wondering big they are intended to actually pay out, or just give the impression of support for energy saving measures.

How being over 60 correlates with inability to afford these things isn't obvious to me. Neither is the support for boiler maintenance / replacement as we contemplate winding down fossil fuel use while omitting support for fitting / upgrading double glazing (unless I missed that .... or may be that's hidden in some other rules!)

Likewise, wonder what they've got against micro hydro and wind? Two great technologies (in the right locations) for winter generation, yet support withdrawn under this scheme.

 

[PITA]

Pita, you sound extremely smug & I don’t blame you, hopefully I’ll be feeling the same soon.

Yeah, I am smug... but I also earned my smugness through two years of defending my position with people who thought I was some kind of Apocalypse Prepping nut job

Just turns out my timing was absolutely spot on...

 

[Avendit]

Yeah, I am smug... but I also earned my smugness through two years of defending my position with people who thought I was some kind of Apocalypse nut job

apocalypse nut job/accurately predicted future cost of electricity
tomayto/tomahto

Smugness well deserved. You sound almost as smug as I do when I explain the rules about claiming mileage in an EV

 

[PITA]

apocalypse nut job/accurately predicted future cost of electricity
tomayto/tomahto

Smugness well deserved. You sound almost as smug as I do when I explain the rules about claiming mileage in an EV

This cheers me up in January, when you hit that 'sweet spot' and you're running the house completely off Solar...

 

[goRt]

However, if the householder is over 60, the Powerwall and PV Panels will be charged at 5% VAT irrespective of the labour materials split. Not all installers know this.

Energy-saving materials and heating equipment (VAT Notice 708/6)

How to account for VAT if you’re a contractor or subcontractor installing energy-saving materials and grant-funded heating equipment.

www.gov.uk

Please show me where batteries are covered within this legislation.

I read it that it's maybe only with PV???

 

[RedMod3]

Please show me where batteries are covered within this legislation.

I read it that it's maybe only with PV???

The whole installation is a single supply (of battery and PV) so one job/project so 5%. If you do the PV on one invoice and the battery with another supplier or invoice or at a later date, then the battery attracts 20% VAT. This is how many companies operate.

 

[megd]

Zappi and Wallbox Pulsar Plus are two that do just that.

Intact, pretty easy to heat water or charge car before allowing export.

Problem is afaik 6amp is lowest charge current at which most cars can start charging. I think that is actually part of the type 2 AC spec.

If your car sits near your charge outlet during the day, vehicle charging would possible do away with the need to have a battery storage system (ok, so no night electricity for the house, but if you are using all the electricity you generate, that might be good enough.

That’s right @Battpower , and exactly my plan.
Any excess generated will firstly be taken by the Wallbox to charge the M3 (when it needs any charge), and then if that’s full or I don’t plug car in then hot water diverter will kick in to take excess.

That 6A minimum may be an issue in the winter, but actually the Wallbox does allow for an “ECO” setting which seems to supplement excess solar with grid power when needed - so at least you make some saving.*

Then I’m also going to get water diverter, so in summer it might manage to do our hot water too. We’ll see, but might even be able to switch the biomass boiler off during warmer months (if very lucky!)!

So in essence we’ll kind of have two “batteries” sitting there to take excess solar. Might end up exporting some, and will still need to buy during dark hours, but still reckon it’ll save us £s over the year with the interest free loan and energy price increases.

*Wallbox site says:

Eco Mode​

Minimize the use of grid power while charging your EV by combining it with any surplus green energy available. Eco mode detects the green energy that is not being used elsewhere in your home in real-time and mixes it with energy from the grid to ensure a fast, efficient charge.

See: Eco-Smart Solar EV Charging

 

[Avendit]

That’s right @Battpower , and exactly my plan.
Any excess generated will firstly be taken by the Wallbox to charge the M3 (when it needs any charge), and then if that’s full or I don’t plug car in then hot water diverter will kick in to take excess.

That 6A minimum may be an issue in the winter, but actually the Wallbox does allow for an “ECO” setting which seems to supplement excess solar with grid power when needed - so at least you make some saving.*

Then I’m also going to get water diverter, so in summer it might manage to do our hot water too. We’ll see, but might even be able to switch the biomass boiler off during warmer months (if very lucky!)!

So in essence we’ll kind of have two “batteries” sitting there to take excess solar. Might end up exporting some, and will still need to buy during dark hours, but still reckon it’ll save us £s over the year with the interest free loan and energy price increases.

*Wallbox site says:

Eco Mode​

Minimize the use of grid power while charging your EV by combining it with any surplus green energy available. Eco mode detects the green energy that is not being used elsewhere in your home in real-time and mixes it with energy from the grid to ensure a fast, efficient charge.

See: Eco-Smart Solar EV Charging

How do all these systems fight it out amongst themselves? My charger can put a clamp around the supply and use that to determine when to initiate charging, and I think a water diverter would do the same? Do they end up fighting between themselves?

 

[Battpower]

How do all these systems fight it out amongst themselves? My charger can put a clamp around the supply and use that to determine when to initiate charging, and I think a water diverter would do the same? Do they end up fighting between themselves?

There is usually a minimal permitted / target threshold for import or export.

So for example one of my inverters aims to hold export down to 25 to 50 watts (configurable). Immersuns (probably others too) are set to turn on diverter whenever export goes above say 150 watts. They keep nudging up the diverted load (immersion heater, EV) until export drops below 150 watts.

I not sure that all algorithms of different kit work well together, but I have Nedap, SolaX, Victron and Immersun kit all working fine together.

It is possible to misconfigure thresholds such that the hybrid storage just dumps battery energy into the immersion heater so a bit of care is needed setting up. Even with normal operation a bit of battery energy probably gets diverted during the backing off phase, but not enough to worry about.

 

[Battpower]

Wallbox does allow for an “ECO” setting

Yes. I haven't looked into the fine details about that configuration, but while cheap night rates are available I think I'd rather make sure the house is being supplied by winter sun when available, heat water with any excess (in fine incremental steps that maintain near zero export) and just charge the car over night.

Paying 3 or 4 times over night rate just to be able to use a bit of PV output during sunny spells doesn't seem sensible in many cases.

 

[Dilly]

Following a dark dismal day yesterday which produced just 480Wh of solar, today was a respectable 9kWh. The Powerwalls got down to 40% yesterday and topped up on cheap rate. Today the Outlander got topped up, the washing machine & tumble drier ran and the Powerwalls were at 94% by tea time.
Wife has done a shed load of cooking and run the dishwasher since and we’re now at 62%. Average overnight draw is only about 300watts with the house on tickover. At 00;30 all hell will break loose as the Powerwalls and the Model 3 start topping up. Should be around a 15kW draw!

 

[PITA]

Following a dark dismal day yesterday which produced just 480Wh of solar, today was a respectable 9kWh. The Powerwalls got down to 40% yesterday and topped up on cheap rate. Today the Outlander got topped up, the washing machine & tumble drier ran and the Powerwalls were at 94% by tea time.
Wife has done a shed load of cooking and run the dishwasher since and we’re now at 62%. Average overnight draw is only about 300watts with the house on tickover. At 00;30 all hell will break loose as the Powerwalls and the Model 3 start topping up. Should be around a 15kW draw!

Like reading a page out of my own life

All hell breaks loose at 00:30 for 4 hours

 

[Avendit]

There is usually a minimal permitted / target threshold for import or export.

So for example one of my inverters aims to hold export down to 25 to 50 watts (configurable). Immersuns (probably others too) are set to turn on diverter whenever export goes above say 150 watts. They keep nudging up the diverted load (immersion heater, EV) until export drops below 150 watts.

I not sure that all algorithms of different kit work well together, but I have Nedap, SolaX, Victron and Immersun kit all working fine together.

It is possible to misconfigure thresholds such that the hybrid storage just dumps battery energy into the immersion heater so a bit of care is needed setting up. Even with normal operation a bit of battery energy probably gets diverted during the backing off phase, but not enough to worry about.

It sounds like it should be possible to fineness with a combination of detecting exports and maybe timingings? But Zappi/Eddi don't think its going to work:

Eddi will automatically take the energy first as less power is needed to start putting power into the water.

Eddi needs 50/100W of surplus power to start a cycle whereas a car charger needs 1.4kW due to the regulations of EV charging.

There is no workaround to allow the Anderson to take priority sadly.

 

[Battpower]

It sounds like it should be possible to fineness with a combination of detecting exports and maybe timingings? But Zappi/Eddi don't think its going to work:

My Victron inverter has a parameter called Grid Set Point which basically says what the inverter will export, even from batteries regardless of what else is going on. I've chatted several times to Zappi designer (ex Immersun) so I may run it by him.

I'm replacing one of my charge outlets with a Wallbox Pulsar so I'll soon know how it behaves with the other kit.

I'm hoping that rather than fight with eachother, there will be a clear bias so I just need to turn one device on or off to control if spare electricity goes to car or water heating.