Solar and Battery Storage are they viable ?

[Mike4]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

[scrumpyjack]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

If that set up is like my solar panels, it will only work whilst there is power from the mains supply.
You would need to ensure that your system is set up so it works even if the grid is turned off, which might be expensive.

[Mike4]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

If that set up is like my solar panels, it will only work whilst there is power from the mains supply.
You would need to ensure that your system is set up so it works even if the grid is turned off, which might be expensive.

I guess my thoughts were prompted by the spare LiFePO4 battery I have lying about from the boat I sold recently, coupled with the week-long power cut I had here in the hovel back when we had the winds. A solar panel and an inverter and I'm back in business with 230Vac again should SSE muck me about again with the leccy supply.

[jaizan]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

Security of supply is a concern for me too. However, if a battery stores 8 kWh, it's just over a day's consumption. Also, the solar output will be negligible on some of the dark winters days when we need the electric the most and the risk of power cuts could be at it's highest. So I think it merely reduces the risk, but not so much when we need it most.

Meanwhile, when I've travelled to countries like Myanmar with a dodgy electric supply, this was typically solved by having diesel backup generators outside hotels and the homes of anyone with money. That's improving security of supply.

[PrefInvestor]

We have a 4k solar PV system and am on the FIT scheme having got our installation done in January 2019 just beating the March 2019 closure of the FIT scheme. The system is very efficient and generates roughly 5000Kwh (units) worth of electricity per year around 70% of which is exported. During the summer months from around April to the end of September on a sunny day the panels produce enough electricity for all of our daytime use. But in winter the days are shorter and not so many are sunny, so generation is significantly reduced. Before we had the panels our usage was 8-10 units per day, in summer that has typically reduced to 4-5 units per day, that being almost entirely our night time usage. Annual usage has reduced from 3,300 units to 2,200 units now.

The FIT scheme pays us about 7p ATM for every unit that we generate, even if we use it ourselves. In practice that figure is made up of ~4p per unit generation tariff plus a ~6p per unit export tariff. But we are paid on the 50% deemed export arrangement (as we have no export meter) and so we are effectively paid half the export tariff for everything we generate (about 5000 units per year) on the assumption that 50% of it is exported. All these figures go up with RPI in April of each year and are guaranteed for 20 years, which is nice. The figures rose by 7.5% in April 2022. Those who have had their panels longer will be on earlier versions of the FIT tariff which were far more generous.

Crunching the numbers on all that on 2020 electricity prices I reckon that the payback time was about 17 years. But with the soaring price of electricity I expect that to change dramatically. With prices double what they were the payback time should now come down to roughly 8.5 years I suspect. And I don’t see electricity getting any cheaper for various reasons:-

1. The desire to reduce gas usage and eventually phase it out completely.
2. The rise of Electric Vehicles, which will now make electricity the new petrol. It’s surely only a matter of time before the Government will want to move Fuel Duty to electricity or they will lose a huge income stream.
3. Electricity will slowly become the only fuel used to power everything. I reckon the price paid for it is bound to increase as a result.

We are now awaiting installation of battery storage which I am hopeful will be able to be fully charge during daylight hours each day (using electricity that is currently exported) and then be able to use this to meet our nighttime electricity needs without recourse to the grid.

I am also hoping at some point to get on one of these smart tariffs that will allow cheap bulk charging of the battery overnight to reduce our winter grid usage. However there are many factors at work here with regard to smart meters and smart tariffs and we are taking things slowly - moving one careful step at a time and not taking any irreversible actions (like getting smart meters) unless it’s clear that doing something is clearly going to save us money.

ATB

Pref

[Mike4]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

Security of supply is a concern for me too. However, if a battery stores 8 kWh, it's just over a day's consumption. Also, the solar output will be negligible on some of the dark winters days when we need the electric the most and the risk of power cuts could be at it's highest. So I think it merely reduces the risk, but not so much when we need it most.

Meanwhile, when I've travelled to countries like Myanmar with a dodgy electric supply, this was typically solved by having diesel backup generators outside hotels and the homes of anyone with money. That's improving security of supply.

Having lived on my boat using solar and lithiums for a few years I'm fully in agreement, other than to say using 8kWh in a day is profligate wasting of energy! Should push ever come to shove regarding energy supply I used to manage on the boat perfectly well on less than 1kWh per day, generated by solar in summer and a portable petrol generator in winter. Sometimes a whole lot less than 1kWr too, and I could happily go back to doing that if necessary, just by moving back onto the boat! As I did in fact back in Feb when I had the week long power cut here in the hovel.

[AF62]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

Thought you might be interested in this from a Facebook group I subscribe to -

We have been using our EV (Kia EV6) Which has a 3500w Inverter built into the car and can output direct to the house via a reverse charge type 2 cable run to the consumer unit via a grid disconnect switch.

(Basically only the car or the mains can power the house for safety both cannot be on at same time)

We charge at night on Go Faster from 8.30pm to 1.30am (Car has a 77Kwh usable battery so can get about 50% of a charge in that time)

When we are out the house runs at a base load around 100w nothing we can do to mitigate that at the moment as we dont have Solar or Battery.

When we are at home during peak rate hours car is plugged into the house and all supply is drawn from the car (Grid is fully disconnected), Car can supply a constant 3.5Kw per hour with Peaks of 7kw for short periods.

Our Non EV Charging usage is about 7kw in a 24 hour period so from full the car could run the house for about 10 days if needed before a recharge (Major power disruption etc).

As we tend to be out in the mornings we tend to plug the car in around Noon and run the house till cheap rate at 8.30pm this has bought our daily peak use down to around 2kw or less (See bill page attached).

We cant have Solar (Roof totally wrong), but I am considering a small (5kwish) home battery to run the load when the car is not available. But till then this is how we are doing it and its saving us around 5kw at peak rates a day.

Not huge savings while we are on the 5.5p Night 13.7p day rates but as the rates jump up next year the savings will increase no doubt.

Just wanted to show how we get around peak rate without having Solar/Battery, Yes there is the initial high cost of the car but we have that anyway, so when its sitting on the drive doing nothing it can at least contribute something back.

Also the other feature of having mobile 240v you can have a brew in the remotest parts of the country.

[Spet0789]

We are looking at installing solar and/or battery storage. I have tried to assess real payback.

If one is looking at payback periods with a cold financial eye, one must deduct the income that one could have earned by investing the capital elsewhere.
I would say at the moment, 5% would be a yardstick.

V8

I would love to know where I can get 5% pa risk free, RPI indexed for 25 years! Marcus pay 0.7% gross, taxable, not indexed in any way.

Not only risk-free but tax-free! Any investment that reduces your costs is effectively providing a post-tax return at your marginal rate.

[Mike4]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

Thought you might be interested in this from a Facebook group I subscribe to -

We have been using our EV (Kia EV6) Which has a 3500w Inverter built into the car and can output direct to the house via a reverse charge type 2 cable run to the consumer unit via a grid disconnect switch.

(Basically only the car or the mains can power the house for safety both cannot be on at same time)

We charge at night on Go Faster from 8.30pm to 1.30am (Car has a 77Kwh usable battery so can get about 50% of a charge in that time)

When we are out the house runs at a base load around 100w nothing we can do to mitigate that at the moment as we dont have Solar or Battery.

When we are at home during peak rate hours car is plugged into the house and all supply is drawn from the car (Grid is fully disconnected), Car can supply a constant 3.5Kw per hour with Peaks of 7kw for short periods.

Our Non EV Charging usage is about 7kw in a 24 hour period so from full the car could run the house for about 10 days if needed before a recharge (Major power disruption etc).

As we tend to be out in the mornings we tend to plug the car in around Noon and run the house till cheap rate at 8.30pm this has bought our daily peak use down to around 2kw or less (See bill page attached).

We cant have Solar (Roof totally wrong), but I am considering a small (5kwish) home battery to run the load when the car is not available. But till then this is how we are doing it and its saving us around 5kw at peak rates a day.

Not huge savings while we are on the 5.5p Night 13.7p day rates but as the rates jump up next year the savings will increase no doubt.

Just wanted to show how we get around peak rate without having Solar/Battery, Yes there is the initial high cost of the car but we have that anyway, so when its sitting on the drive doing nothing it can at least contribute something back.

Also the other feature of having mobile 240v you can have a brew in the remotest parts of the country.

The way things are going it seems almost worth buying an electric car just to park on the drive to get this! An old Leaf with an old and tired would probably work quite well as domestic mains demand is quite a light load compared to driving around.

[BullDog]

Given the way world events are going the decision to buy a solar system charging a Powerwall or similar is more than just financial. Security of supply at all is my concern.

Yes the leccy might get prohibitively expensive and one hesitates to use it, but in addition having a battery charged up by the sun could be a very reassuring thing, worth more than just money.

Thought you might be interested in this from a Facebook group I subscribe to -

We have been using our EV (Kia EV6) Which has a 3500w Inverter built into the car and can output direct to the house via a reverse charge type 2 cable run to the consumer unit via a grid disconnect switch.

(Basically only the car or the mains can power the house for safety both cannot be on at same time)

We charge at night on Go Faster from 8.30pm to 1.30am (Car has a 77Kwh usable battery so can get about 50% of a charge in that time)

When we are out the house runs at a base load around 100w nothing we can do to mitigate that at the moment as we dont have Solar or Battery.

When we are at home during peak rate hours car is plugged into the house and all supply is drawn from the car (Grid is fully disconnected), Car can supply a constant 3.5Kw per hour with Peaks of 7kw for short periods.

Our Non EV Charging usage is about 7kw in a 24 hour period so from full the car could run the house for about 10 days if needed before a recharge (Major power disruption etc).

As we tend to be out in the mornings we tend to plug the car in around Noon and run the house till cheap rate at 8.30pm this has bought our daily peak use down to around 2kw or less (See bill page attached).

We cant have Solar (Roof totally wrong), but I am considering a small (5kwish) home battery to run the load when the car is not available. But till then this is how we are doing it and its saving us around 5kw at peak rates a day.

Not huge savings while we are on the 5.5p Night 13.7p day rates but as the rates jump up next year the savings will increase no doubt.

Just wanted to show how we get around peak rate without having Solar/Battery, Yes there is the initial high cost of the car but we have that anyway, so when its sitting on the drive doing nothing it can at least contribute something back.

Also the other feature of having mobile 240v you can have a brew in the remotest parts of the country.

The way things are going it seems almost worth buying an electric car just to park on the drive to get this! An old Leaf with an old and tired would probably work quite well as domestic mains demand is quite a light load compared to driving around.

Maybe I am wrong, but I think the capability of using the car as energy is pretty new technology and I doubt it's available in an older Nissan Leaf?

As an aside, I understand Nissan themselves are repurposing used Leaf batteries that are removed into domestic battery storage arrays.

[AF62]

Maybe I am wrong, but I think the capability of using the car as energy is pretty new technology and I doubt it's available in an older Nissan Leaf.

Correct.

It is only new cars like the Kia EV6 that has the ability ‘out of the box’ to do this and even then I believe the adapter that creates a 3 pin socket you have to plug into the charging point is an optional extra.

That isn’t saying you couldn’t do it with something older, but it is probably cheaper to just buy a house battery rather than the car and all the electronics needed to do it.

[scrumpyjack]

I am now looking at getting a Powerwall installed. It now gives mains security in that in the event of a power cut the house continues to have mains supply from the Powerwall, though limited to about 5kw. We get frequent power cuts here in rural Hertfordshire so although the economics of having a Powerwall are marginal, the avoidance of powercuts makes it attractive.

Does any one know what the VAT situation is? I have a feeling it is now zero rated, but perhaps only if you have solar installed at the same time? We already have solar but could perhaps add more if there is a VAT saving.

I suspect there is a long delivery delay for Powerwalls?

[DrFfybes]

I am now looking at getting a Powerwall installed. It now gives mains security in that in the event of a power cut the house continues to have mains supply from the Powerwall, though limited to about 5kw. We get frequent power cuts here in rural Hertfordshire so although the economics of having a Powerwall are marginal, the avoidance of powercuts makes it attractive.

Does any one know what the VAT situation is? I have a feeling it is now zero rated, but perhaps only if you have solar installed at the same time? We already have solar but could perhaps add more if there is a VAT saving.

I suspect there is a long delivery delay for Powerwalls?

First, check you can run your solar/powerwall if the supply fails. You may need some extra kit as you have Solar because most installations are required to isolate if the supply fails. This is to stop you feeding back into the grid when the sun comes up and the poor chap mending the wires suddently gets fed from 1500 solar panels.

Second - yes VAT free only applies to "green" installtions, which is the main reason we're having batteries in with our solar panels rather than waiting a year to see if the price comes down and having to pay VAT as an add-on.

Paul

[funduffer]

Consider this.

Say you have solar panels and a cheap overnight/off-peak tariff. By exporting your excess solar you can earn 12p (Scottish Power) or even 15p (Octopus) per kWh. Your overnight/off-peak tariff may be something like 30p per kWh during peak and 7.5p or maybe 9.5p during off-peak hours (Octopus tariffs).

If you consider buying battery storage, then with these rates, there is no advantage in charging the battery from your solar - it is better to charge it during off-peak hours.

Say you purchased a 5kWh battery for £5K (just as an example).

You would charge the battery during off-peak and it would cost say, 7.5p * 5kWh = 37.5p
You would discharge the battery during peak hours and save say, 30p * 5kWh = 150p
So you would save 150p - 37.5p = 112.5p per day.

Assume that, every day, you could completely discharge the battery, and fully recharge it during off-peak hours (best case scenario).

It would take you 5000/1.125 days to recoup your investment, or 4444 days, or 12 years - best case scenario!

I would not buy a storage battery based on these data, but I might if the relevant rates changed such that the payback was more like 6 years.

FD

[BullDog]

Consider this.

Say you have solar panels and a cheap overnight/off-peak tariff. By exporting your excess solar you can earn 12p (Scottish Power) or even 15p (Octopus) per kWh. Your overnight/off-peak tariff may be something like 30p per kWh during peak and 7.5p or maybe 9.5p during off-peak hours (Octopus tariffs).

If you consider buying battery storage, then with these rates, there is no advantage in charging the battery from your solar - it is better to charge it during off-peak hours.

Say you purchased a 5kWh battery for £5K (just as an example).

You would charge the battery during off-peak and it would cost say, 7.5p * 5kWh = 37.5p
You would discharge the battery during peak hours and save say, 30p * 5kWh = 150p
So you would save 150p - 37.5p = 112.5p per day.

Assume that, every day, you could completely discharge the battery, and fully recharge it during off-peak hours (best case scenario).

It would take you 5000/1.125 days to recoup your investment, or 4444 days, or 12 years - best case scenario!

I would not buy a storage battery based on these data, but I might if the relevant rates changed such that the payback was more like 6 years.

FD

Yes indeed. On pure financial terms none of it makes much sense when the money spent on batteries could be invested to generate income to help pay the energy bill. I guess by the time the battery pack has paid for itself in 12 years time, it's time to replace the batteries with new ones. So they'll never pay for themselves.

On the other hand, the money that was invested on day 1 still exists after 12 years and is still producing income. With luck, the invested capital after 12 years might even be worth more than on day 1.

A disappointing outcome in some ways, but it's reality nonetheless.

[DrFfybes]

Consider this.

Say you purchased a 5kWh battery for £5K (just as an example).

You would charge the battery during off-peak and it would cost say, 7.5p * 5kWh = 37.5p
You would discharge the battery during peak hours and save say, 30p * 5kWh = 150p
So you would save 150p - 37.5p = 112.5p per day.

FD

I think the cheap overnight rates have a higher day rate, and a lot of the really cheap overnight rates are only available if you have a car charger, but the rest of your maths s pretty sound. If you can get 5% on the cash used to buy the battery then that is a better investment at current rates. This also assumes you can discharge your battery or export to the grid before recharging, which most ystems don't (AFAIK) allow - battery is topped up before export.

But as you say - who knws what rates will be in 10 years. I expect export rates to drop as domestic solar becomes more common, but with rates being treble what they were a year or so ago I don't know if they'll go up much in the next 5 years.

We're getting a battery as it is VAT free with teh solar, and if security of supply becomes an issue (and we get power cuts out here once a year anyway) then I can get an auto switchover to keep the fishtank and freezer on for a say or 2

Paul

[csearle]

I've just helped (a tiny bit) install a gadget (with a battery) near Lingfield that charges up its battery with solar power then, after that, runs a meter backwards exporting to the grid but only until the meter reaches zero. It also charges the battery at night at the night rate if needed.

During a power outage the thing can supply up to 5kW for as long as its battery has charge. Some heavy loads are via a consumer unit directly connected to the grid, which wouldn't enjoy a backup during an outage, but most of the circuits are downstream of this gadget.

Initial things I've heard sound good. It's only been running for two weeks or so, so I think the jury is still out.

Chris

[servodude]

I've just helped (a tiny bit) install a gadget (with a battery) near Lingfield that charges up its battery with solar power then, after that, runs a meter backwards exporting to the grid but only until the meter reaches zero. It also charges the battery at night at the night rate if needed.

During a power outage the thing can supply up to 5kW for as long as its battery has charge. Some heavy loads are via a consumer unit directly connected to the grid, which wouldn't enjoy a backup during an outage, but most of the circuits are downstream of this gadget.

Initial things I've heard sound good. It's only been running for two weeks or do so I think the jury is still out.

Chris

Did you have to handle the anti-islanding yourself or are these gadgets smart enough now to do that for you?

[PrefInvestor]

Consider this.
Say you have solar panels and a cheap overnight/off-peak tariff. By exporting your excess solar you can earn 12p (Scottish Power) or even 15p (Octopus) per kWh. Your overnight/off-peak tariff may be something like 30p per kWh during peak and 7.5p or maybe 9.5p during off-peak hours (Octopus tariffs).

If you consider buying battery storage, then with these rates, there is no advantage in charging the battery from your solar - it is better to charge it during off-peak hours.

Well funduffer your calculations seem to completely exclude consideration of the solar panels other than to say it’s not worth using them !.

We have 4KW solar system and it can fully charge our 8.2Kw battery (at zero cost), fully power the house and export 200-300 KWh per month to the grid as well in the summer months (Apr – Sep). Using a cheap off peak tariff might be good in the winter months, though the new Octopus Flux tariff you can get paid 19.3p for your export and 31.4p during the 16:00-19:00 peak time slot. There are issues though with smart meters, loss of inflation proof FIT payments and the fact that it’s a variable tariff and can be varied by them any time they see fit – so we are still on their standard variable tariff (SVT) tariff ATM.

In summer we are currently using only 1-2 units per week from the grid, somewhat more in the winter, but with the FIT tariff paying ~£350 per year (rising with inflation for the next 20 years) overall our annual electricity bill is now less than £100 per annum. And that’s just on the SVT using the battery to do grid input minimisation, if we move to Flux (and importing and exporting to take full advantage of that tariff) then we would I estimate that we might make perhaps £200-300 a year profit – but it’s complex to estimate the exact savings on Flux and there are issues and risks.

Regarding payback time, before the panels and battery we used about 3,400Kw per annum, on the latest SVT that would cost about £1,300 a year. So if we made say £200 on Flux then we’d be saving say £1,500 a year. Total cost of the solar plus battery was about £14,000. So payback time is probably about 9-10 years.

But then what is going to happen to electricity prices in the coming years ?. Electricity is clearly going to eventually become the ONLY fuel used to power everything - especially cars. When that happens the Government is going to put the current fuel duty paid on petrol onto electricity instead, it’s not going to want to give that up. So I can only see electricity prices rising still further in future, our solar/battery move removes the financial risk of that.

ATB

Pref

[stevensfo]

Consider this.
Say you have solar panels and a cheap overnight/off-peak tariff. By exporting your excess solar you can earn 12p (Scottish Power) or even 15p (Octopus) per kWh. Your overnight/off-peak tariff may be something like 30p per kWh during peak and 7.5p or maybe 9.5p during off-peak hours (Octopus tariffs).

If you consider buying battery storage, then with these rates, there is no advantage in charging the battery from your solar - it is better to charge it during off-peak hours.

Well funduffer your calculations seem to completely exclude consideration of the solar panels other than to say it’s not worth using them !.

We have 4KW solar system and it can fully charge our 8.2Kw battery (at zero cost), fully power the house and export 200-300 KWh per month to the grid as well in the summer months (Apr – Sep). Using a cheap off peak tariff might be good in the winter months, though the new Octopus Flux tariff you can get paid 19.3p for your export and 31.4p during the 16:00-19:00 peak time slot. There are issues though with smart meters, loss of inflation proof FIT payments and the fact that it’s a variable tariff and can be varied by them any time they see fit – so we are still on their standard variable tariff (SVT) tariff ATM.

In summer we are currently using only 1-2 units per week from the grid, somewhat more in the winter, but with the FIT tariff paying ~£350 per year (rising with inflation for the next 20 years) overall our annual electricity bill is now less than £100 per annum. And that’s just on the SVT using the battery to do grid input minimisation, if we move to Flux (and importing and exporting to take full advantage of that tariff) then we would I estimate that we might make perhaps £200-300 a year profit – but it’s complex to estimate the exact savings on Flux and there are issues and risks.

Regarding payback time, before the panels and battery we used about 3,400Kw per annum, on the latest SVT that would cost about £1,300 a year. So if we made say £200 on Flux then we’d be saving say £1,500 a year. Total cost of the solar plus battery was about £14,000. So payback time is probably about 9-10 years.

But then what is going to happen to electricity prices in the coming years ?. Electricity is clearly going to eventually become the ONLY fuel used to power everything - especially cars. When that happens the Government is going to put the current fuel duty paid on petrol onto electricity instead, it’s not going to want to give that up. So I can only see electricity prices rising still further in future, our solar/battery move removes the financial risk of that.

ATB

Pref

We have 4KW solar system and it can fully charge our 8.2Kw battery

May I ask where you buy such batteries?

My retirement in a year or so will coincide with my large diesel Volvo being rather old and I will be looking for an electric car which will be used for short journeys.

We're lucky in having a large garden and plenty of places to put photovoltaic panels. My idea was to DIY and use them just for the electric car, but I will have to look more closely at the technical details.

Are the prices of these batteries coming down? Last time I looked, they were very expensive.

Steve