Solar Panels UK - is it worth it?

[WannabeOwner]

If I take that £13k and put it in something that we are confident of making 10% annually for 25 years, yep, I make what looks like a fortune - £150k

Except ... you have to pay tax on that investment "income" (unless that is allowed for in your illustration?)

You could probably man math this either way TBH

Important not to assume that either is a dead-duck. The Win / Loss will only be a percentage-point or two, either way, unless one of other tanks.

PV is a guaranteed hedge against electricity price rises - every year you are going to get X kWh electricity from your roof - nothing to pay for that portion of your electricity usage. That's tax free of course.

I wonder how feasible it is for electricity price to go down in real terms? and for investment income (after tax) to (significantly) outperform any rise in energy price?

the wine won't get warm

Sold!

 

[Avendit]

Except ... you have to pay tax on that investment "income" (unless that is allowed for in your illustration?)

It wasn't, although you are around an ISA allowance so may be able to skip some of this. Tho I've never seen an ISA vehicle get near the mythical 10% we are using. Also didn't make allowance for inflation, tho the £94/month withdrawal was inflation adjusted.

 

[RedMod3]

so when you are supplying the grid - what is the rate you are getting?

Deemed 50% of FIT panel set at 5.99p/kWh on 500+ kWhr for the whole of May. I hope to give them less than 20 kWh.

 

[Dilly]

Deemed export, so 50% of generation at 5.55p/kWh whether I actually export it not

EDIT
5.99p/kWh (it went up in April)

 

[RedMod3]

Really thinking we need two threads, one of "solar panels - is it worth it?" and another of "my daily solar generation update and screenshot"

Maybe, but for those thinking of solar, this thread shows that one day you can have a problem of producing too much power and have to give it away to the grid while on another day, you end up not having enough and having to buy it at a dear rate of 15.59p / kWh - this can be an issue if you have just one PW. However, those with 2 PWs have a lot more flexibility. I've been told my second PW won't be here until July and new orders are unlikely to be fulfilled until October.

 

[PITA]

Yep, two Powerwalls is the sweet spot

 

[Avendit]

Maybe, but for those thinking of solar, this thread shows that one day you can have a problem of producing too much power and have to give it away to the grid while on another day, you end up not having enough and having to buy it at a dear rate of 15.59p / kWh - this can be an issue if you have just one PW. However, those with 2 PWs have a lot more flexibility. I've been told my second PW won't be here until July and new orders are unlikely to be fulfilled until October.

'problem' ;-). It is indeed suboptimal, but unlike using power, it's not the end of the world.

 

[Stuart Watson]

Sorry to go back to an old(er) post, but I'm still convinced something in your calcs must be wrong. My ROI graphs are in the thread here:
Solar Panels UK - is it worth it? and where you are you should be able to invest in less panels for better return. You also should have lower heating load which will help in the off times (tho I guess you may have some cooling needs in the summer depending on your house construction, but that is actually better suited to solar).

In my link above I consider 4 scenarios of varying size of array and size of battery to accompany them. At current UK power prices and in Scotland solar only breaks even in ~5.5 years and offers solid returns for ever more. Adding a battery extends your breakeven to more like 7 years, but the profit from that point on is at a higher rate. At some point there will likely be some maintenance costs which I've not factored in, but the battery is warranted to 13 years with my usage pattern.

Assuming power costs stays the same as it is, that's £40k up in 25 years. If power goes up to 50p/KWh then you are at £80k 'profit'. You are very subject to power price fluctuations, but any 'investment' is subject to go up or down, previous returns are not indicative of future etc., This should render somewhere between 2x and 6x return.

With my array, if everything goes pete tong on us I still have power, heat and transport. I'm no prepper but that's quite a lot of security. And if there is a powercut, the wine won't get warm. On top of that there is cutting our carbon footprint. We buy electricity from one of the 'green' suppliers, but that still isn't carbon free, so buying less it better.

If I take that £13k and put it in something that we are confident of making 10% annually for 25 years, yep, I make what looks like a fortune - £150k. But in that time I'm also paying more for electric (so still subject to its fluctuations) and inflation will take the edge off the spending power of that profit (calculating that is beyond my skills). If I want to use that investment to lower my electric bills, I can only take £93.50 a month out of my bill. With solar its £154 a month at todays prices, and at £50p/kwh its £240.

You could probably man math this either way TBH, but there is also a fiduciary duty to do 'the right thing' for us, our kids and the planet we are currently stuck on. You can price that in yourself, or you can wait for the gov to twist your arm and re-align the market.

Avendit…. Thanks for replying! I’ll study your post/graphs . Best wishes

 

[Stuart Watson]

... you have to pay tax on that investment "income" (unless that is allowed for in your illustration?

Use a SIPP or ISA !
Plenty of ways of investing tax free (depending on your country of residency)

 

[Avendit]

Avendit…. Thanks for replying! I’ll study your post/graphs . Best wishes

The battery graphs look much better due to our ability to get low overnight tariffs to charge the battery - the advantage of the battery will be reduced without this if you can't do that where you are. But the battery is also the bulk of the cost, hence why the graphs all cross in much the same areas. I think its around page 24-26 of the thread I've gone more into the level of modelling of -my- usage I went into come to that graph. Mileage will vary drastically for different situations, but same as you wouldn't buy a financial product just on the advertised numbers, I'd say the same for solar.

You need to look at your usage (if you are still in an office 9-5 and can't physically locate a battery anywhere, then you really will struggle with payback) and workout what you can use chap solar or cheap overnight power for, how much disruption you are willing to accept for this, how easy is it to retro-fit solar awareness to your car charger and so on before deciding.

 

[btc1k]

Maybe, but for those thinking of solar, this thread shows that one day you can have a problem of producing too much power and have to give it away to the grid while on another day, you end up not having enough and having to buy it at a dear rate of 15.59p / kWh - this can be an issue if you have just one PW. However, those with 2 PWs have a lot more flexibility. I've been told my second PW won't be here until July and new orders are unlikely to be fulfilled until October.

Probably covered in one post though, rather than a daily post stressing the same point

 

[btc1k]

Yep, two Powerwalls is the sweet spot

I'm not sure it is, for someone with an average consumption.

My own average usage is 14kwh a day outside of off-peak. So one powerwall won't cover it. Two will definitely cover it, either with solar charging the battery or batteries being charged in off-peak, to be then drained in peak.

But £8k for a second powerwall, to offset say 1kWh a day of peak usage? Let's say that's 35p shifted from peak to off-peak. 30p/day saving.

Let's say your peak usage is higher, at 15, or 16 kwh. And you want to shift perhaps 3 kWh a day from peak to off-peak to save 90p/day.

At an extra £8k for an additional powerwall, saving 90p/day... the payback period makes no sense.

I am now anticipating a response saying it's not about the payback period - but for 90% of people, the finances have to make sense and those who will just throw money at it to solve a problem that doesn't make financial sense, isn't much of a goer. That's reality.

 

[novemberRomeo]

A few months back, I signed up for installation of a 9.5 kWp solar system (27 panels, solar edge 8 kw inverter) with 1 Teslapowerwall.
Originally, I was going to only get the solar and not the battery, but after doing the sums on the Tesla Energy Plan, I calculated I would get my money back on the battery within 3 years. Mainly because we are high electricity users in the winter (we use a heat pump for our heating and hot water, and have 2 EVs) and the vastly cheaper import rate makes a huge difference. By using the grid as the battery we can export all the excess power in the summer and not have to worry about using it whilst the sun shines.

This week the installation has begun and on day two the electrician tells me they need to fit a MODBUS meter to limit the export of our system. First time I've been told about any export limitations, so I enquire further.. The DNO have said our export must be limited at 4 kWh.

I am now having a minor panic because this is limiting us to exporting half of what we generate at peak, which will make my numbers look considerably less favorable and push us back in to the situation of needing to try and use up the power whilst the sun is shining rather than exporting it all back on the TEP.

I've questioned the installer about whether anything can be done and they basically said no. Had I have known this I wouldn't have signed up for so many solar panels and would have had a much cheaper installation.

Does anyone have any suggestions on if anything can be done to remove the DNO limit that the installer might not be telling me? Should the installer have told me about the export limitation as part of the quote phase?

 

[WannabeOwner]

... you have to pay tax on that investment "income" (unless that is allowed for in your illustration?

Use a SIPP or ISA !
Plenty of ways of investing tax free (depending on your country of residency)

Indeed, although the tenure of our discussion was based on significant profits and my maths was on the assumption that would exceed tax-free allowances

My SIPP has been maxed out for ages, I'm of that age. We seem to have a problem in the UK where professional people - GPs and the like - get to their 50's,, have accumulated masses of experience, but their tax position is that it is not worth them working more than just enough to pay their bills, so when we could most use them they are incentivised to play golf/etc. instead. Crazy. Senior ranks in the forces, normally retired at 55, who stay on for 3-days-a-week until 60 add maybe £10-20 a month to their pension ... so basically "No point".

My assumption is that money needs to be withdrawn from investment to pay the electricity. I'll also assume "top end" so that this would be in addition to other regular withdraws taken to get the tax-free withdrawal.

If there are no other requirements to withdraw money from investment then its a straight comparison of investment return (allowing for the the withdrawal to pay electricity bill, rather than just letting the capital grow until rainy-day / retirement) and @Avendit says that his illustration wins out even in that scenario.

I went looking for an online calculator that allowed fiddling with PV, Battery and so on. The Energy Saving Trust has one that looked quite good ... but it doesn't then show any detailed workings, only "Total lifetime saving" which makes it hard to compare against an investment. Maybe someone else can find an online calculator, or a google-sheet

I've done / am doing it anyway but I'd be interested in a detailed set of calcs.

(if you are still in an office 9-5 and can't physically locate a battery anywhere, then you really will struggle with payback)

Maybe in Portugal it is worthwhile leaving air con running during the day, to keep the internal fabric / thermal-mass cool, if that would then reduce the cooling effort needed in the evening?

"Cool storage"

 

[WannabeOwner]

Should the installer have told me about the export limitation as part of the quote phase?

I think they should have done. It was a discussion that my installer brought up at the outset - he was not expecting to get my install past the DNO without some sort of restriction ... but turns out they allowed the whole lot, which was a pleasant surprise

Does export limit interfere with being able to use Tesla energy plan?

 

[novemberRomeo]

Does export limit interfere with being able to use Tesla energy plan?

Not directly, but I was hoping to be able to export > 4 kWh during the summer peak season. In the summer, our base load is around 0.5 kWh. So once the powerwall has been charged (which as I understand it, on the TEP, we have no control over when this happens, so it may charge from the grid overnight) we won't be able to utilise the full 8 kWh generation capability, and will be generating 3.5 kWh that we can neither export nor use (without the hassle of constantly trying to use it)

 

[PITA]

I'm not sure it is, for someone with an average consumption.

My own average usage is 14kwh a day outside of off-peak. So one powerwall won't cover it. Two will definitely cover it, either with solar charging the battery or batteries being charged in off-peak, to be then drained in peak.

But £8k for a second powerwall, to offset say 1kWh a day of peak usage? Let's say that's 35p shifted from peak to off-peak. 30p/day saving.

Let's say your peak usage is higher, at 15, or 16 kwh. And you want to shift perhaps 3 kWh a day from peak to off-peak to save 90p/day.

At an extra £8k for an additional powerwall, saving 90p/day... the payback period makes no sense.

I am now anticipating a response saying it's not about the payback period - but for 90% of people, the finances have to make sense and those who will just throw money at it to solve a problem that doesn't make financial sense, isn't much of a goer. That's reality.

Most people think this way, but that's not the main issue.

It's not the storage capacity that makes it clever... it's the 10kW discharge capability.

If you had one Powerwall, you're restricted to 3.6kW or 5kW discharge.

So even if your Powerwall is full, brimming 13.5kWh of energy stored... if you then turn on an 8kW electric shower (or a 7kW car charger, or 7kW induction cooker, or 3.5kW Emersion heater)... the Powerwall can only deliver 5kW... so anything over 5kW has to come from Solar excess or Grid at peak rate.

Let's say your base house demand is 2kW during Winter with Heat Pump active. You've then only got 3kW capability left, to keep you away from Grid Power. For us, that isn't enough.

In Summer, you might stand a chance with Solar... but in Winter, two Powerwalls give you that extra capability to stay off-grid at Peak Rate costs.

That's why two Powerwalls are the sweet spot.

 

[ACarneiro]

Should the installer have told me about the export limitation as part of the quote phase?

IMHO they should have, yes.
Mine went through all the process of contacting my DNO to confirm the maximum export before the works were agreed.
I think you could argue that it makes a material difference to your system and as such you may have grounds for some level of dispute (he says, being in no way knowledgeable in consumer law).

 

[RedMod3]

'problem' ;-). It is indeed suboptimal, but unlike using power, it's not the end of the world.

I like the situation to have filled

Most people think this way, but that's not the main issue.

It's not the storage capacity that makes it clever... it's the 10kW discharge capability.

If you had one Powerwall, you're restricted to 3.6kW or 5kW discharge.

So even if your Powerwall is full, brimming 13.5kWh of energy stored... if you then turn on an 8kW electric shower (or a 7kW car charger, or 7kW induction cooker, or 3.5kW Emersion heater)... the Powerwall can only deliver 5kW... so anything over 5kW has to come from Solar excess or Grid at peak rate.

Let's say your base house demand is 2kW during Winter with Heat Pump active. You've then only got 3kW capability left, to keep you away from Grid Power. For us, that isn't enough.

In Summer, you might stand a chance with Solar... but in Winter, two Powerwalls give you that extra capability to stay off-grid at Peak Rate costs.

That's why two Powerwalls are the sweet spot.

I agree PITA, and in Island mode, with a quiescent draw of 1.1kW in summer, 3.9kW gives nowhere near enough buffer; my installer reminded me of this when I was considering ordering the second PW. In winter, with both heat pumps running, we draw a basic 2.3kW; one PW would not be sufficient for either peak load or to see us through the peak rate period.

 

[RagingWhisky]

Similar style thinking on the setup this end.

17kWh storage on top of the solar side, however looking to up that to 35 in the coming months ('sweet spot' with regards to the usual peaks/trough loads in the house).

DNO export maxxed to 6kw, but in winter time will only get about as far as 6-8 hours 'normal' usage (with heat systems on the go).

/Tin Foil Hat Mode
If the geopolitical side 'kicks off' (worse than at present) then you could imagine electricity/gas/coal supplies being tightly maintained to ensure any impact mitigation. In that kind of scenario, having the capability to run without grid draw would be something to consider including in quotes (not to mention handy in the event of black/brown-out)