The Solar Thread

the ROI on removing a working system boiler and tank to fit a combi will buy alot of gas.

if the tank has an immersion – you could rig that up to solar – but at current rates your better off just selling the solar and buying the gas. Gas is about 1/3 the price per kw than you can get paid from octopus.

But either way if the roof points south id spend the money on solar over putting a combi in place of a working system boiler. .

my biggest regret in my house refurb was fitting a combi tbh ( we had a non working system boiler though)

Retrofitting a solar thermal coil is a non starter and using a standard coil with solar thermal is inefficient. heat transfer isnt quick enough to pull a good Delta T

I have a Gledhill 250l direct solar tank in situ waiting to be plumbed in + a grant sahara two panel system on order. – ill advised likely on costs and projected life spans but its about self sufficiency and minimising ongoing costs in out future – that said the majority of the kit is benign and its only the moving parts that wear out in given time as oppose the whole system

My simplistic notion was that the PV could run the immersion heater somehow (I’m assuming its got one)?

it can – but its cheaper to use the gas and sell the power to the grid…..

Okay, thats the info i was after – brilliant stuff guys!

@rockhopper – if it’s got one then yes you could do that.

IF the tank is pressurised (i.e. there’s no header tank in the loft and the hot water system is main pressure) then it could be relatively simple to have the cylinder swapped for a double coil one and you could go for solar thermal – I installed my own a year ago and it produces plenty of hot water over the summer months.

However I have a feeling that the previous owners will have put the electric show in because it’s a gravity fed hot water system with little pressure.

Trying to work out if I should cough up for another battery, as they’re back in stock at the moment. £1000 for another 2.4kWh is a lot though, and I doubt I’d ever make it back. But it would mean the house would never draw from the grid outside of off-peak times. At the moment cooking hammers the 5.2kWh setup I’ve got in the winter months.

On the other hand £1,000 buys a lot of air fryers and the electricity to run them.

Buying a battery still feels a bit of a gamble, who knows what the export tariffs will look like over the next 5 yearsish…? 😏
Having said that, we just turned on our setup for the first time yesterday with a 15KW battery, so we’ll see how it works out in the short term. 😁

At the moment, you’ll have an indirect cylinder and for PV heating, you’d want direct, or better still, both.

That’s not really correct …. I have an indirect cylinder with an immersion and the PV heats it up splendidly – there’s no need to change.   In fact I’ve just look at the immersion switch light  in the utility room and it’s glowing a solid red meaning the tank is up to about 63c just from diverted PV today.

My simplistic notion was that the PV could run the immersion heater somehow

Yes it can…. just fit a diverter system – there’s a number out there.

That’s not really correct …. I have an indirect cylinder with an immersion and the PV heats it up splendidly – there’s no need to change. In fact I’ve just look at the immersion switch light in the utility room and it’s glowing a solid red meaning the tank is up to about 63c just from diverted PV today.

Only if the tank has an immersion backup and even then, it’s not efficient.

Buying a battery still feels a bit of a gamble, who knows what the export tariffs will look like over the next 5 yearsish…?

If anything the battery makes more sense than solar panels – costs of electric long term as demand grows and our country does the square root of sod all to secure our energy. Will go up.

Being able to load shift will be a godsend.

One week into having Flux export live here in South Leeds. Broadly we are generating 2x what we are using (69kW exported in a week). Taking into account import costs and standing charge, Flux has still MADE US over £19 last week.
If you want more info then pics are on twitter: @chb_leeds

I’ve just started the switch to Flux today. We have a large array (good) but an EV to charge (bad) and use electric heating (bad). I think it’ll work out well in summer when the high export tariff and lots of generation compensate for charging the car being more expensive than a normal overnight tariff, but as soon as it starts getting colder next winter we’ll be back on Go.

Only if the tank has an immersion backup and even then, it’s not efficient.

Sorry I didn’t know that direct tanks ever came without an immersion.

Re “efficiency” why, because the element isn’t at the bottom of the tank?

Frankly I couldn’t GAS about efficiency if I’m getting free hot water – no way would I buy another tank just to get the immersion a few inches lower.

I changed to Flux about a month ago but I’m still waiting to get paid for exports. Chased Octopus on Thursday and they told me they are still waiting on Mpan from the DNO.

Anyone else had to wait this long? I’m exporting 20 Kw most days at the minute.

Sadly it can take a while as many of the DNOs are a complete shambles when it comes to doing this. We’ve been waiting months from SSEN.

@leegee we are in the same boat.

Chased Octopus on Thursday and they told me they are still waiting on Mpan from the DNO.

That appears to be the script.

When I pushed them on the fact they were provided with an existing export mpan they hung up.

They also won’t respond to Twitter on the same question.

I think they are just overwhelmed with integrating all the bulb customers

Anyone know the limitation of obtaining an export tariff on a system associated with the old Feed in Tariff schemes?
My system was installed in 2014, and has a generation meter recording PV inverter output. The FiT payments go to the supplier of the system, as it was a free install.

Confused by this statement on octopus website, “If you have started receiving FiT payments in the last 12 months, the FiT rules mean you won’t be able to switch to Outgoing Octopus just yet”. I thought the FiT subsidies for new installs stopped several years ago.

My system was installed in 2014, and has a generation meter recording PV inverter output. The FiT payments go to the supplier of the system, as it was a free install.

It’s not yours to move the payments.

Yep, I’m doubtful it’s even your system at all.

You get as much generation as you can use and the suppliers get the FIT.

You can’t change any of the system either i.e. change the inverter to fit batteries.

(And no-one in their right mind would change from an existing FIT from that era to anything else.)

Frankly I couldn’t GAS about efficiency if I’m getting free hot water

Its not quite free (i have the same system by the way) as you could send that excess back to the grid.

I don’t need to.

The old FIT system assumes 50% of your production goes to the grid and that’s what we get paid [an insane amount of money per kWh] for regardless of what actually goes back.

The benefit of being an early adopter!

I’m on Flux and my fag packet calculations tell me I am saving around £10 per day as per this week. Obvs solar dependent etc. Ironically I am drawing more from the grid as I force charge my batteries overnight. Previously I didn’t always do this. I dont draw any from the grid outside this window and export solar until the sun sets.

The benefit of being an early adopter!

Forgot about that… Lucky ****** 🙂

@surfer are you force charging all year? Is that so you get the most export?

@nixie We have only had our PV and battery since November 2022 so not a full years experience yet. Also we have changed tariffs a couple of times since then, from a Flexi tariff to Eco7 then to Flux so the circumstances have changed as have the seasons.
In the most part though yes one way or another I have used lower price energy overnight to either protect us from higher prices during the day or more recently to be able to be self sufficient and feed back to the grid to make us money/offset bills.

Sounds good.

I’ve just this morning got an email confirming access to the solaredge battery control beta. Not had a chance to play yet but a quick scan of the documents looks promising. Seems like you can configure different cost periods to charge cheap and avoid grid usage as well as having a monthly plan. I think there is an element of smart learning in their system based on usage and perhaps expected generation so the battery will only force charge enough to cover usage (i.e. so you’ll get the most from any production).

Is there much to tell between the different manufacturers of inverters and batteries?  Around where we are the two main suppliers are SolarEdge and Huwawei and I think I would lean towards SolarEdge but happy to be educated

There’s a good spreadsheet here which helps judge whether Go / Flux etc is better for you.

Tariff Calculation Spreadsheet

I’m still on Go at the moment. Over the last eight months my average unit price has been 9p/kWh.

I’m still on Go at the moment

Assume you have an EV? We dont yet so I should imagine that would change things for us.

Re FiT system, yes I’m fully aware the system is not “mine” and the solar company get the FiT payment. I’d actaully forgotten about the 50% deemed export rule, I imagine they claim that as well, with an account tied to the MPAN of the generation meter. Do FiT payments and deemed export payments come from same source?
Fair enough. Reality is of course I export very little, most of the free to me energy gets used or diverted to water heating. Really sunny days when the whole 300 litres reaches max temperature there will be more exported, but not often.

I’m thinking along the lines if I had installed a second independent system with batteries how that would work, no doubt its now got complicated, if not impossible, to get any export credit.

BTW, the rules regarding modifications / replacement parts in FiT systems has changed, any “improvement” gained is factored out from the payments. Something like this had to be done, as inverters or panels could fail in the 25 year contract period.

You could replace broken kit like for like but not replace a broken panel with one with a higher output.

General rule is not to mess with anything!

I imagine they claim that as well, with an account tied to the MPAN of the generation meter.

That’s all there is basically…. But it is significant.

You could replace broken kit like for like but not replace a broken panel with one with a higher output.

On panels I didn’t own … I wouldn’t even be doing that.

If nothing else it would be convenient if the birds were to peck away at all the wiring and the inverter was to no longer operate. Doubtful the rentaroofers would be back to replace it in a hurry

@leffeboy I suspect not all animals are equal.

I thought about starting a thread on this as the set up I have has many flaws. However, I’ve no experience of others so can’t compare.

My inverter often imports a small amount even if my battery is charged or solar generated which adds up over the day to maybe a kWh.

When I set my inverter to charge the battery to any percentage it ceases to discharge during that period regardless of the level set which makes the feature a bit rubbish as you can’t leave it set e.g. to charge to 50pct in the early hours of the morning from 2am to 3am if the battery is at 70 say, it still draws from the grid for any load between 2 and 3.

The battery and inverter don’t talk to each other properly such that the battery Can overnight fall below 10pct which I don’t think is good for it. Time will tell if it fails- I suspect it will just become less efficient more quickly which will be difficult to prove as faulty unless it fails completely.

Fox system perchance? I can answer some questions.

It has to import a little bit of power to make sure you’re definitely connected to the grid. You can’t avoid this really as the only reliable way is to put a load on it. Not going to change.

You can actually do what you want to do in your second paragraph but you need to either connect your inverter to Home Assistant via RS485, or delve into the settings on the inverter itself.

Third point – it’s really difficult to measure the capacity of LFP batteries. The voltage doesn’t vary linearly with charge level so the only way to know what’s going on is to count electricity in and out. The available capacity does vary with temperature so as that falls (overnight), the percentage available also drops. The inverter will trigger a charge regardless of how it’s configured in order to protect the battery.

They all have decent warranty cover and I wouldn’t be bothered by this at all.

Thanks. It’s a lux and uhome system. The concern I have re the battery is that the inverter doesn’t always kick in.

So the battery can drop to say 1pct- according to the inverter software and battery app. Sometimes the battery software records a low voltage warning. At some point the inverter then realises there is a problem and charges back up to 10pct. They were all logged- I complained and it looks as if they’ve done something to erase the log. Battery still performing the same way albeit less times crashing over night, I guess because there’s now more solar charge in it and it’s warmer.

Re the charging I contacted lux and they seemed to think that operation was correct.

Re warranty- unless something stops working completely I think most solar warranties are going to be difficult to apply, since for example even if the battery takes 3kwh and only gives back 1kwh, how can I prove its not working.

First full week on Flux tariff. Paying roughly £9-£10 per day so this is a circa £10 per day saving which is pretty impressive.

Where did that detail come from @surfer.

Is there much to tell between the different manufacturers of inverters and batteries? Around where we are the two main suppliers are SolarEdge and Huwawei and I think I would lean towards SolarEdge but happy to be educated

Can’t comment on Solar Edge, but we have Huawei and these are the things which annoy me about it.

It does work fine and a nice phone app and web interface, but there is a big PITA:

Only the installer can change the operating mode eg from max self consumption to scheduled charging. You can get round this by resetting the system and over riding the installation password fairly easily, but it’s still a stupid design feature.

However, once you’ve done this you have to connect locally with the unit via it’s own Wifi network to change the mode (another massive PITA). The next PITA is that the phone App won’t let you change any settings until it has updated the firmware and they seem to release new firmware almost daily.

You then hit the next issue, immediately after an update and for several hours later, the system never seems to behave properly. At first I thought the SW was duff but have just come to realise that after every update it basically stops working for a few hours and it back to normal by the next day – this is another PITA as you end up thinking you’ve broken it. If you try a reset it switches everything off and then only bits switch back on e.g last time I had to manually power back up the BMS as only the inverter came back after the reset.

However, if you leave it alone, it just works, so can’t really complain too much.

I do also notice that the speed at which the battery kicks in to power stuff seems quite random. If I switch the kettle on, sometimes it’s instant and our energy meter just says zero, other times it basically doesn’t seem to notice the kettle has swicthed on and by the time it’s boiled, it’s too late. Our smart meter claims we use about 0.2 kWh a day when running on battery, so the ‘leakage’ isn’t too bad..

Another thing, it’s a closed Huawei system, so no hooks / API for any IFTTT integration (that I know of). The inverter and BMS talk to Huawei central and your app connects to that server to find out what’s going on. No local interface.

Around where we are the two main suppliers are SolarEdge and Huwawei and I think I would lean towards SolarEdge but happy to be educated

We have two Solaredge inverters. One failed after about three months use and was replaced under warranty quickly and with no hassle so I can recommend Solaredge’s warranty service. Other than that the operation of the two inverters has been faultless and the dashboard software is simple but effective.

@nixie Its from an app called “Octopus Watch” its £1.99 for Android. I have the data already but it saves me a lot of spreadsheet work. Its challenging even with Home Assistant to work out when exactly power is exported and with 3 different tariffs over 24 hours it would be quite difficult.