Powerwall versus Givenergy batteries

[ringi]

Octopus Flux changes what I want from a battery system, as advoiding imports and maximum output between 3pm-7pm is not easy to program with many batteries.

That and I had a fully fitted quote of £35,000 for a solar edge system with 24 panels, inverter, smart water and a 10k SE battery.

Looking at prices it seems a GivEnergy battery inverter and battery is cheaper then just adding a battery to an existing solar edge inverter. No point having any system to heat water from PV as Flux makes it better to export the PV and heat water at off peak rate.

 

[WannabeOwner]

I just look at what happens to my electrons now and see what could make it better.

Well I reckon that as the sun increases (day duration and insolation "power"), over the coming months you'll have the problem of avoiding export and need a list of overflow uses to prioritise as a solution (or just let it export of course). A battery only helps up to the point where it is full! so absence of a battery just means that the solution is needed earlier in the day.

That is moot if the number of panels is small, relative to usage, and for most people the restriction is probably the size of the roof (because incremental cost of "more panels" is modest in overall cost calculation), and maybe for many/most? an immersion heater is enough.

My panels produce peak of about 15kW at midday in mid summer, and the house use is 1.3 - 2kW ... it doesn't take long to fill a couple of powerwalls, and gives me about 1,000 miles a month into the cars ... but that requires that the cars have battery space available on the days when we get wall-to-wall sunshine.

For smaller / bigger systems the problem is the same, just relative.

 

[phil4]

Well I reckon that as the sun increases (day duration and insolation "power"), over the coming months you'll have the problem of avoiding export and need a list of overflow uses to prioritise as a solution (or just let it export of course). A battery only helps up to the point where it is full! so absence of a battery just means that the solution is needed earlier in the day.

That is moot if the number of panels is small, relative to usage, and for most people the restriction is probably the size of the roof (because incremental cost of "more panels" is modest in overall cost calculation), and maybe for many/most? an immersion heater is enough.

My panels produce peak of about 15kW at midday in mid summer, and the house use is 1.3 - 2kW ... it doesn't take long to fill a couple of powerwalls, and gives me about 1,000 miles a month into the cars ... but that requires that the cars have battery space available on the days when we get wall-to-wall sunshine.

For smaller / bigger systems the problem is the same, just relative.

Luckily I've 5kW max from the PV, and with two Tesla's, I reckon I can use a good chunk of summer sun to keep them full. At the moment I'm using oil filled rads to soak up any over generation, but of course that's not good in summer. I don't have a hot water tank, so nothing going there.. So yes, am listing things I can do to soak up the extra.

I take your point on batteries, however here's my thinking. At the moment, there's a chunk morning and evening at peak rate (40p), which the solar can't help with. Then in the middle of the day, I can end up exporting. With batteries (sized appropriately for daily use), I should be able to use the batteries morning and evening, so no peak rate there, and then solar midday. If I were at that point I'd be a lot less worried about exporting.

 

[WannabeOwner]

If I were at that point I'd be a lot less worried about exporting.

OK ... but beware that you might find that it IS a religion when you get there

 

[Pete UK]

Looking at prices it seems a GivEnergy battery inverter and battery is cheaper then just adding a battery to an existing solar edge inverter. No point having any system to heat water from PV as Flux makes it better to export the PV and heat water at off peak rate.

Yes, I think you’re right on GivEnergy.

I’m concentrating on nailing down a good install price incl. batteries for a GivEnergy system at the moment. Will look at tariffs later (as they are changing all the time). I think the off-peak tariffs will be around for a long time (haven’t they been about for decades already?). So for me as a high user (19,000kW pa), big old Victorian house, non ideal orientation roofs, with a model Y. I need a big array and BIG battery storage, with fast battery charging capacity to benefit the most !
The key I’ve realised is being able to store it all for your own use later.

The new AC GivEnergy ‘All in one’ battery looks good (when it’s finally released) a Powerwall killer perhaps? With a new install Hopefully soon, I’m planning on going DC on the batteries though to save 5-10% on the extra DC/AC/DC conversion losses. That’s a lot of kW lost (£) !

Unfortunately one size doesn’t fit all. Everyone’s requirements for a system are different. And with an EV, that’s 4,500 kW a year extra right there ! Zero petrol but more kW ! Maybe a heat pump later…?

If your lucky enough to have a super efficient home like @WannabeOwner has, then needs are polar opposite to the rest of us, where the use of solar and a battery to save the generated kW for later in the summer and cheap off peak import to last as long as possible till the next off peak rate in winter is paramount and where you will make the really massive savings.

Like previously mentioned, exporting/ finding something to artificially (waste?) use the excess on for those few over generation days/ weeks in the summer is insignificant compared to being short 20-30kWh @40p/kW per day for 4 months in the winter every day because you couldn’t buy it cheap and store it in a battery.

Needs are different for everyone, as are solutions, quotes and pricing; It’s such a complex problem on an individual basis. I’d like to get a solution where I’m generating the most, saving the most, not faffing with forecasts and manually adjusting house power loads, battery charging, etc. everyday, not obsessing with using things at certain times of the day and just generally living a normal life like before Solar PV !

 

[Chimpy McChimp]

That's exactly where I am at. Once the system is installed the most I want to do is sit back and marvel at how much money I am saving

 

[Pete UK]

That's exactly where I am at. Once the system is installed the most I want to do is sit back and marvel at how much money I am saving

I think you might need to do a bit of battery tuning during the seasons, but once a month or so should be ok

 

[ringi]

I think you might need to do a bit of battery tuning during the seasons, but once a month or so should be ok

I think a system can run on Octopus Flux without the need for any tuning once it is setup.

 

[WannabeOwner]

just generally living a normal life like before Solar PV

Once the system is installed the most I want to do is sit back and marvel at how much money I am saving

That's fine provided you don't want an optimal solution.

A system that gets juice from multiple sources, where some sources are cheaper but only available for part of the day - and where there is some, limited, storage for other times - it seems to me that it will need to know what the consumption is going to be in order to "stock up". When I go to the Supermarket I check the shelf to see if we are low on any of the staples ... if we have people coming I get some extra beers in ... similar to that I think. I, and many others, already made a lifestyle change yesteryear to setting white goods on an overnight schedule to take advantage of Off Peak. Plenty of people do washing and ironing only on sunny days. Yesteryear, before tumble driers, everyone only did washing on dry days!

Otherwise just live your life, and when that coincides with Sunshine it will be paid for by PV, and when not then purchased from Grid at the tariff rate.

I hate seeing my system export ... that's basically the top-and-bottom of it, for me

 

[ringi]

Remember on Octopus Flex daytime export pays a little more then of peak import, so you can never lose out by putting too much charge into the battery at off peak time

 

[Pete UK]

Everyone is truly so different !

Oh, but I do want an optimal system. Depends on what ‘your’ optimal is.
If you’re ‘optimal’ involves doing stuff overnight or staying in to charge the car for free from excess solar, and watching weather forecasts and adjusting what I do to other times. That’s not ‘optimal’ to me. That’s non-optimal. Some people have work and lives to live.

For me, my optimal is reducing the cost of my electricity the most and saving the most.
This will come at a cost, yes. Maybe much more than others but this will bring greater savings overall without too many lifestyle changes. Payback is only a calculation that is a future forecast. It might be much sooner or much later as and when prices change.

I’ve never done the washing or put the dishwasher on overnight to save a few pence and I suspect the majority still don’t. Off peak tariffs used to make bugger all difference, as everything was off or on stby mode during the small hours of the night. So for most people (non-Solar) they were probably on a single rate tariff, as that worked out cheapest overall.

Things have changed now. For most people I imagine energy costs have only now made people consider Solar and batteries and time of use.

Hopefully I never have to load shift anything. (Except the car charging!) which we’ve always done at night, so that won’t change.

I want to use things when I want to use them - not only when the suns out or between 0030 and 0430. To enable this batteries are required and big ones !

Cheers !

 

[yessuz]

I did my man maths today.

I took the high usage day where I consume on daily basis my usual consumption and will need 50 kwh in total to charge my car.

off-peak let's say 50 kwh
peak - 12 kwh (washing/drying during the day (help me...), teenage daughter forgets the towel rail on (face palm) and so on...

with this in mind, if I had EVERY SINGLE day whole month, it would cost me now 10.51 gbp a day / 315 a month.
If I offset all this with solar and batteries, then my daily cost would be ~4 gbp and up to maybe 120 gbp a month (car and batteries at offpeak rate, and all dayly usage is covered by solar/batteries

If I take financing for solar installation, with current banking rates and such, it would be ~220 a month for like 13 kilo pound cost of system..

so in such terms I would be almost break even on a month.. otherwise I see this as for 5 years I would be paying ~220 month in order to save ~80 a month. so -140 off the pocket as "investment".

it is a lot of money in general... 8000 buys a lot of electricity :/

is there anything I am missing here?

 

[WannabeOwner]

teenage daughter forgets the towel rail on (face palm)

Replace face-palm with timer? Probably tricky because it will be within the wet-zone and need something fancy rather than just a smart plug.

Simple push-button which gradually pops back out (like the buttons in stairways for lighting) might do?

car and batteries at offpeak rate, and all dayly usage is covered by solar/batteries

No excess PV to dump to car at some times of the year? (Or maybe the car is "at work"?)

If I take financing for solar installation

Cashing in savings would be better (by my man maths) ... no tax on the "return on investment" ... but assumes you have some of course ...

is there anything I am missing here?
...
8000 buys a lot of electricity

That viewpoint is spot on.

I've made / saved money on everything I ever did that was Eco ... but I have been an early adopter every time, which meant on the one hand that I needed a specialist (Corgi boiler guy wasn't skilled,-up, at that time) and on the other we didn't have the Demand far outstripping Supply / Skills, as we have at present, which is jacking up the price. And coupled with that Oil price shot up after I installed biomass boiler at huge expense (2008) ... Putin / Ukraine did same for electricity and sorted out the ROI for my PV ... plus I had the benefit of driving EV from 2015 way ahead of anyone that I knew

So apart from JFDI I'm not sure there is a sound reason ... if you are approaching retirement age, and in a forever-home, then spending capital now to reduce outgoings later may be reassuring. I no longer pay 80% of my electricity bill and car fuel. If oil price plummeted I'd probably be miffed, but either way I'm still only paying 20% of my total electricity / car fuel usage. Recent inflation will have increased what that 20% is costing me ... and the saving on the 80% that I am no longer having to pay.

 

[yessuz]

Replace face-palm with timer? Probably tricky because it will be within the wet-zone and need something fancy rather than just a smart plug.

it is on the timer 2 hr boost. it reverts back to previous state. so if you are off, press button, heats for 2 hrs and turns off. but it you fail and instead of 2 hr boost you firstly turn ON then 2 hr boost, after 2 hrs it will revert to previous state - ON
This is one of those: Amazon.co.uk

No excess PV to dump to car at some times of the year? (Or maybe the car is "at work"?)

It this case, excess would be dumped into car... but is it worth it, if feed in tariff from Octopus is 15p? is it the same rate I would have if I am on IO?!
in this case, I would dump all my excess into grid and would take that 5p margin when charging my batteries up and car over night :/

Cashing in savings would be better (by my man maths) ... no tax on the "return on investment" ... but assumes you have some of course ...

...

That viewpoint is spot on.

I've made / saved money on everything I ever did that was Eco ... but I have been an early adopter every time, which meant on the one hand that I needed a specialist (Corgi boiler guy wasn't skilled,-up, at that time) and on the other we didn't have the Demand far outstripping Supply / Skills, as we have at present, which is jacking up the price. And coupled with that Oil price shot up after I installed biomass boiler at huge expense (2008) ... Putin / Ukraine did same for electricity and sorted out the ROI for my PV ... plus I had the benefit of driving EV from 2015 way ahead of anyone that I knew

So apart from JFDI I'm not sure there is a sound reason ... if you are approaching retirement age, and in a forever-home, then spending capital now to reduce outgoings later may be reassuring. I no longer pay 80% of my electricity bill and car fuel. If oil price plummeted I'd probably be miffed, but either way I'm still only paying 20% of my total electricity / car fuel usage. Recent inflation will have increased what that 20% is costing me ... and the saving on the 80% that I am no longer having to pay.

no, still couple of decades + before retirement but this might be the forever home...

I am just still contemplating if it's worth biting the bullet to dish out 13k/250 month in order to save 80 pounds a month for the next 5 years :/

 

[spon88]

Replace face-palm with timer? Probably tricky because it will be within the wet-zone and need something fancy rather than just a smart plug.

Simple push-button which gradually pops back out (like the buttons in stairways for lighting) might do?



No excess PV to dump to car at some times of the year? (Or maybe the car is "at work"?)



Cashing in savings would be better (by my man maths) ... no tax on the "return on investment" ... but assumes you have some of course ...



That viewpoint is spot on.

I've made / saved money on everything I ever did that was Eco ... but I have been an early adopter every time, which meant on the one hand that I needed a specialist (Corgi boiler guy wasn't skilled,-up, at that time) and on the other we didn't have the Demand far outstripping Supply / Skills, as we have at present, which is jacking up the price. And coupled with that Oil price shot up after I installed biomass boiler at huge expense (2008) ... Putin / Ukraine did same for electricity and sorted out the ROI for my PV ... plus I had the benefit of driving EV from 2015 way ahead of anyone that I knew

So apart from JFDI I'm not sure there is a sound reason ... if you are approaching retirement age, and in a forever-home, then spending capital now to reduce outgoings later may be reassuring. I no longer pay 80% of my electricity bill and car fuel. If oil price plummeted I'd probably be miffed, but either way I'm still only paying 20% of my total electricity / car fuel usage. Recent inflation will have increased what that 20% is costing me ... and the saving on the 80% that I am no longer having to pay.

I "loosely" calulated ROI and it's 8 - 10 years ish. But we're retiring several years early and in a home we don't expect to move from, just upgrade now the kids are gone and not trashing everything. The self-sufficiency aspect is very appealing as is the technology, so for us it's the right thing to do. If we were tighter on cash, we'd maybe think again but fortunately we're at the point in life where we can experiment a bit without too many worries. Oh and anything that's got decent green credentials and isn't helping fund a war, must be good!

 

[Chimpy McChimp]

I am just still contemplating if it's worth biting the bullet to dish out 13k/250 month in order to save 80 pounds a month for the next 5 years :/

I guess the other unknown is what happens with electricity prices in the next few years. It was straightforward for me as I am thankfully on a low fixed rate until next year. But at that point I know my rates are likely going to double (or near enough) so anything I can do to reduce that raise is worth considering. That said. I am taking advantage of 12 year interest free loans from Scottish government which makes the maths a little more palatable!!

 

[WannabeOwner]

it is on the timer

teenage daughter forgets the towel rail on

As you were then!!

but is it worth it, if feed in tariff from Octopus is 15p? is it the same rate I would have if I am on IO?!

Sorry, had forgotten you had that opportunity. Its beyond my Man maths ...

I am just still contemplating if it's worth biting the bullet to dish out 13k/250 month in order to save 80 pounds a month for the next 5 years :/

I think the debate would be much easier if spending savings, rather than borrowings ...

The only gain I see is that you are locking in your £80 a month, whereas inflation / rising electricity will make that worse if you delay. But who knows how much that might be - or if it will turn negative.

 

[ben_c]

It this case, excess would be dumped into car... but is it worth it, if feed in tariff from Octopus is 15p? is it the same rate I would have if I am on IO?!
in this case, I would dump all my excess into grid and would take that 5p margin when charging my batteries up and car over night :/

You can’t be on Go / IO and get the 15p feed in, only the bog standard 4.1p SEG they have to give to anyone.

 

[Mrklaw]

try a switchbot for the towel rail. I have one attached to the towel rail switch for the bathroom - there is a humidity sensor in the bathroom because my daughter forgets to turn the towel rail *on*. So I have an automation (home assistant) that if the humidity hits 80% that means she’s having a shower, and it triggers the switchbot to turn the towel rail on. It runs a timer to try and turn it off but its not very good at that (strong switch, less strong bot) but she normally has one quite late so I’m ok letting it run overnight during off peak and then turn it off in the morning.

 

[Tony Hoyle]

Your feed in and tariff are unrelated (except for things like TEP) - it doesn't even have to be with the same company. I get my feed in from bulb and am on IO.