Solar Panels UK - is it worth it?

[WannabeOwner]

what are those 10kw appliances?

Good point. Looking back through last few weeks consumption I have no spikes over 10kW

Charge PowerWall and Car would do it immersions probably uses a fair bit and I suspect if we have both ovens on, several hob rings, and perhaps washing etc.

PowerShower might do it for people who have those?

Arc welding? Melting salt?

 

[Pete UK]

But seriously what are those 10kw appliances?

1x car charging and
1x cooker ?

However, I’d expect the car charging would be done 99% of the time during off peak.

Pretty much never going to need that much for any sustained period of time.

@gidster99 - I’d try and push to get those smart meters installed ASAP. If your suplier
Won’t do it, change supplier and insist.
Took me ages to get them to finally replace ours that stopped working after 2 months. That was about 2 years ago. Today they are coming to replace (SSE, now OVO).
Regards consumption, check to see when your hot water tank is being heated (if it has immersions) and if you have underfloor heating mats, if it’s a big area, they use a hell of a lot too.

 

[yessuz]

1x car charging and
1x cooker ?

However, I’d expect the car charging would be done 99% of the time during off peak.

Pretty much never going to need that much for any sustained period of time.

@gidster99 - I’d try and push to get those smart meters installed ASAP. If your suplier
Won’t do it, change supplier and insist.
Took me ages to get them to finally replace ours that stopped working after 2 months. That was about 2 years ago. Today they are coming to replace (SSE, now OVO).
Regards consumption, check to see when your hot water tank is being heated (if it has immersions) and if you have underfloor heating mats, if it’s a big area, they use a hell of a lot too.

if charger is before consumer unit, and solar is after, then solar inverter will not see the car (you can trickle charge car from granny though)

 

[WannabeOwner]

separating the savings of the solar and the battery so that you can work out whether having both or them individually will be worth it for you, despite some saying that solar is a no brainer, that isn't the case for everyone

I've got the lot - also including Solar Thermal both hot water and pool ... done originally for Eco reasons, but since then (I started in 2007) first price of oil sky rocketed (thanks for that!) and latterly Electricity price (thanks for that too! it brought my PV purchase payback down to under 5 years)

But good points you have raised, and I've seen people post numbers which show that, for them, just battery was the best bang-for-buck

I think there is risk that overnight Off Peak tariff goes away (as EV charging increases mopping over supply North Sea wind during the night) and the best Time-of-Use rate will then be "mid day" (sun shining and wind blowing), which for people with solar panels and battery won't be as good as an overnight Off Peak rate (unless battery & PV is big enough to charge from PV and support house overnight in Summer)

EVMan has some useful "Whiteboard comparisons" on YouTube of cost/payback for both Solar and Battery

 

[WannabeOwner]

if charger is before consumer unit, and solar is after, then solar inverter will not see the car (you can trickle charge car from granny though)

Does that lose ability to dump excess PV into EV?

 

[yessuz]

Does that lose ability to dump excess PV into EV?

well, not really / at extent/it depends..

you will not be able to use your standard car charger because it is always supplied from the grid...
but you can use granny charger and have constant 2.5 kw supply to the car... as this is in the same loop with inverter/solar. or maybe, upgrade/add one commando at 16 A or 32 (both within same loop) - then you can even have more supply (up to 7 kw) to the car straight from sun/battery... but you do not want to charge your car from the battery

so imho, it's actually best this way - night straight from grid with low tarrif, house supplied from batteries overnight.

 

[WannabeOwner]

you can use granny charger

Ah, you said that, I see the point now. Too much hassle for me to have to switch them over though and my API bodging takes care of not charging Car from Battery, but yeah! ... most people would probably see my API-bodging as same-but-different amount of hassle as swapping Granny and Wall chargers

 

[Mrklaw]

non ideal roof......11kwp solar. I'd love to have a roof as non-ideal as that lol!

I don't get SEG due to the stupid lease solar on the south side so I want to avoid overcharging - but normal installs thats a good point which mitigates just charging it up to 100% every night (although in summer 50% may be enough for non-high users)


hopefully you have a separate meter for the tenants - at least for my own information even if its on the same bill I'd want to know.

 

[WannabeOwner]

hopefully you have a separate meter for the tenants

I hate anything that is "inclusive" (often labelled as "Free"!) - so often abused.

 

[Mrklaw]

I hate anything that is "inclusive" (often labelled as "Free"!) - so often abused.

when electric was cheap its easy enough to do but can lead to people not paying attention. If you could meter separately and even isolate those circuits so they're grid driven and cross-charged, that could lower your effective coverage needed for your part of the house.

depends what you want to do - first step is modelling usage

 

[WannabeOwner]

can lead to people not paying attention

Indeed. leave an electric fire on, or not bothering to fix a leaking tap (if on Water Rates) ... no need to care if not paying "per unit"

 

[gidster99]

All of these points with regard to the tenant are very valid. But for us, she actually gets into her flat by coming through the front door and walking up the stairs to the loft...so finding the right tenant is of paramount concern. Thankfully, we have a perfect person: super respectful, super-quiet and very conscientious indeed...For example, she lets us know when she is away so we can turn the heating off in the flat. So I am pretty sure she is not abusing heat / water / electricity etc. But you are correct in that it is something to watch out for!

 

[Mrklaw]

good point. And thats the kind of thing you can make a reasoned call on with the right data. A mix of IHD/CT clamps on critical circuits (like tenant), and some smart plugs on big devices or even on groups of devices can fill in gaps pretty quickly.

I monitor things like the tumble dryer separately, but also have a couple behind the TV unit just monitoring 'AV cabinet and lighting'. Just going down that tree diagram of generation until I get to the twigs where its not practical to go much more detailed.

 

[Chimpy McChimp]

We also use a similar amount of electricity as you (11,000) but we have a hot tub....!!!

 

[PITA]

If it helps anyone's planning... this is our setup, which I think is pretty much perfect for us.

Detached house on Single Phase consumer unit. Pretty much everything is electric, but still has Gas Boiler Central Heating system for Winter use.

Heat Pump (Air to Air) provides heat & cooling through internal wall units. So operates independently to Gas Central Heating system. Ideal to reduce Gas use through year.

Smart Meter installed with Dual-rate tariff (7.5p off-peak / 39p peak) with Intelligent Octopus.

Two Tesla Powerwalls battery storage and a Tesla Gateway 2. This backs up the whole house on Single Phase. 27 kWh of storage / 10 kW of charging and discharging power for the house.

Solar Array with 5kW inverter which powers the house and charges the Powerwalls during Summer.

7kW Ev Charger installed onto the Tesla Gateway 2 which allows Grid Charging to ev, Battery Charging at 7 kW to ev, and Solar Excess charging to ev. We use this all the time in Summer to move excess solar into the cars.

Then we upgraded the Grid Service cables to 3 Phase. Our cutout is 80 amps per phase and connects to a 3 Phase distribution board outside.

2 x 22 kW ev chargers (3 Phase) connected to the 3 Phase distribution board. Grid only fast charging. This is upstream of the Battery Storage, Solar Array & consumer unit. So Intelligent Octopus can schedule charging at anytime without affecting the home battery storage systems. You can basically fast charge at any time on these.

Although we have Solar Heating (MyEnergi Eddi)... it isn't used, as all excess goes into cars.

The overall result of this setup is the ability to use 98% of generated solar throughout the year. Plus download huge electricity power, at the same time, to multiple battery storage devices at night, during the cheap rate without load balancing.

A really nice balanced system.

 

[PITA]

Just to add...

This setup gives us redundancy if one ev charger suddenly fails and needs to be repaired.

It allows us to still charge a car from battery & solar during a Grid Blackout.

With 10kW discharge capability we never have to go to Grid Power at peak rate.

3 Phase allows capacity to fast charge without load balancing.

We also use SpaceX Starlink for Broadband Internet failover during a blackout. As mobile phone data services cannot be relied on (they only backup power for voice calls).

 

[Drew57]

Our DNO application wait is coming up to a month now…. Grrr.

When I recently applied for additional panels on the garage roof (lower so no scaffolding required), I was informed that DNOs have 45 days to respond. Approval was given last week (on day 43) after the installer chased up twice for me.

 

[Js1977]

if charger is before consumer unit, and solar is after, then solar inverter will not see the car (you can trickle charge car from granny though)

Does that lose ability to dump excess PV into EV?

It's all about the the right charger and CT clamps. It does not mater where your charger is electrically wired in order to use excess PV.

 

[Pete UK]

if charger is before consumer unit, and solar is after, then solar inverter will not see the car (you can trickle charge car from granny though)

Yep. Plenty of options. Personal preference and lifestyle dictated I guess. Personally I didn’t buy an expensive wall charger so that I could hang a wire out of my front window to potentially save 2.5p per kW on the import/ export differential ! Plus the car probably won’t be there all day.
But it’s a very good point and a valid option for someone who, is maybe WFH or is retired, to squeeze every last free Solar drop out of the system.


That said, I’m fed up of paying £6,500 a year for electricity, so if I can save £4,500 a year or more by going after the big stuff I’m all over that. I’ll worry about if I’m spending £155 or £165 a month later on. (Probably won’t).

It’d be good to have the flexibility to quickly
dump some kW out of the battery into the car at 7kW though, to make space for the solar. Rather than a long tiny trickle or drawing from the grid at peak prices (Although I expect that would be like 5 days max in the summer ). For example if you were arriving back from work Fri evening with a low car battery and then immediately off away for the weekend. So the home battery would get replenished by Solar for free, while you’re away.

There is a lot to think about for sure. And everyone has completely different needs, usage, roof space, efficiency and budgets and expectations. There are some super low users with super high efficiency houses out there that possibly can focus in more detail. That’s less critical to some high users with large, less efficient much older houses, that’s can’t alter too much in a cost effective way, that just need to urgently get a suitable system that is a best compromise to reduce their bills dramatically. Oh and yes, of course because we all want to save the planet.

 

[Pete UK]

Joy of joys - after waiting over 6 months to have our smart meters gone dumb replaced, the guys showed up for 5 mins, said they are working fine and buggered off. Despite all our protests to the contrary !

Congrats SMA PLC (on behalf of OVO).
Hours more in the chat and on the phone again now….

….Slow clap - totally p***ed off.