How big's your power store?
Discussion
Idle Christmas musing on electricity costs and was wondering how many on here have battery power stores and of what size?
I have an EV, but no V2L capability...but it got me thinking about charging batteries up overnight and then powering the house from them.
(Not so fussed on solar, but that would also be an option).
So, who has battery banks on here, and how big are they?
We use a fair bit of electricity, so savings could be significant even just with the difference between peak and low rates.
I have an EV, but no V2L capability...but it got me thinking about charging batteries up overnight and then powering the house from them.
(Not so fussed on solar, but that would also be an option).
So, who has battery banks on here, and how big are they?
We use a fair bit of electricity, so savings could be significant even just with the difference between peak and low rates.
I’ve heard the term “load shifting” to describe what you’re talking about.
We’ve just had two large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
When everything is running the hope is that on a typical cold winter’s day (4deg where we live) we wont be paying more than the overnight discounted rates. We shall see.
In summer I think we’ll be effectively off grid for a few months, partly enabled by having batteries running the house overnight (charged from solar during the day) and also by having large enough batteries that we can go for a couple of days without drawing from the grid when there’s not much solar production.
We’ve just had two large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
When everything is running the hope is that on a typical cold winter’s day (4deg where we live) we wont be paying more than the overnight discounted rates. We shall see.
In summer I think we’ll be effectively off grid for a few months, partly enabled by having batteries running the house overnight (charged from solar during the day) and also by having large enough batteries that we can go for a couple of days without drawing from the grid when there’s not much solar production.
Edited by Cheib on Monday 30th December 10:01
Cheib said:
I’ve heard the term “load shifting” to describe what you’re talking about.
We’ve just had tow large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
When everything is running the hope is that on a typical cold winter’s day (4deg where we live) we wont be paying more than the overnight discounted rates. We shall see.
In summer I think we’ll be effectively off grid for a few months, partly enabled by having batteries running the house overnight (charged from solar during the day) and also by having large enough batteries that we can go for a couple of days without drawing from the grid when there’s not much solar production.
That's broadly the sort of thing that has my cogs whirring...and I was thinking similar sized batteries.We’ve just had tow large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
When everything is running the hope is that on a typical cold winter’s day (4deg where we live) we wont be paying more than the overnight discounted rates. We shall see.
In summer I think we’ll be effectively off grid for a few months, partly enabled by having batteries running the house overnight (charged from solar during the day) and also by having large enough batteries that we can go for a couple of days without drawing from the grid when there’s not much solar production.
Would be interested in photos of the install and how it pans out
I have a need to replace a garage soon (have kicked that can almost as far as possible) and accommodating batteries and maybe putting in PV (would be a South facing large roof) is starting to seem quite attractive.
Cheib said:
I’ve heard the term “load shifting” to describe what you’re talking about.
We’ve just had tow large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
That's a massive system, do you mind sharing how much, over £30k I suspect? Or do you get economicies of scale as you up the kWh?We’ve just had tow large ASHP’s installed, in January we’re getting solar and batteries installed. Pretty hefty battery system, 64 kWh
We have a 5.6KW solar PV and one Powerall (12.5kWh usable), not enough to get us through a whole day in winter with the house full, on Xmas day lasted only till last 1pm. I think we need about 30kWh to reliability stay off on-peak electricity, that's no including gas heating, though when the house occupancy is back to just us, sub 20kWh should be enough.
gangzoom said:
That's a massive system, do you mind sharing how much, over £30k I suspect? Or do you get economicies of scale as you up the kWh?
We have a 5.6KW solar PV and one Powerall (12.5kWh usable), not enough to get us through a whole day in winter with the house full, on Xmas day lasted only till last 1pm. I think we need about 30kWh to reliability stay off on-peak electricity, that's no including gas heating, though when the house occupancy is back to just us, sub 20kWh should be enough.
[Img]https://live.staticflickr.com/65535/54235431628_f072a96107_c_d.jpg[/thumb]
Prices on storage are coming down quickly. 30kWh for £6k batteryWe have a 5.6KW solar PV and one Powerall (12.5kWh usable), not enough to get us through a whole day in winter with the house full, on Xmas day lasted only till last 1pm. I think we need about 30kWh to reliability stay off on-peak electricity, that's no including gas heating, though when the house occupancy is back to just us, sub 20kWh should be enough.
[Img]https://live.staticflickr.com/65535/54235431628_f072a96107_c_d.jpg[/thumb]
https://www.fogstar.co.uk/collections/solar-batter...
Evanivitch said:
Prices on storage are coming down quickly. 30kWh for £6k battery
https://www.fogstar.co.uk/collections/solar-batter...
That's look like great value, as long as it's not the battery storage equipment of a cheap eBike battery....I'm presuming it's got some kind of safety testing compliance? Our PowerWall is pretty close to the gas mains and main house fuse. Given a 500 Wh ebike battery can burn your house down, I'm assuming there is some kind of UK regulations for home battery storage? https://www.fogstar.co.uk/collections/solar-batter...
The Tesla Powerall is complaint to some kind of industry standard I believe.
https://www.ul.com/services/ul-9540a-test-method
Road2Ruin said:
I have a 9.5kwh battery, probably 9kwh useable, and even in the winter usually only drain it if the missus is not supervised with the washing machine. However, the house is about as energy efficient as you can get for a 1930s property. Completely refurbished about 4 years ago.
If you are using less than 9kWh a day at this time of year you must be keeping the spirit of scrouge alive and well .On Xmas day peak drain was nearly 10KW, I wasn't even at home at this point, and the main cooker hubs are gas along with gas heating!!
Edited by gangzoom on Monday 30th December 07:26
dave123456 said:
I’d have thought the most important question is what’s the ROI period?
That’s a moving target with tariff changes…We have 12kW array and newly installed ASHP to heat an outbuilding. Without the ASHP we pull approx 30kWh/day, ASHP usage pattern is yet to settle down (still screed drying) but at present is pretty much doubling consumption.
I keep looking at adding storage to our system (hybrid inverters and appropriate cabling already installed) and can’t decide between:
5kWh - smoothing of PV generation during daylight hours, avoid any peak rates in summer.
10kWh - as above, but avoid peak rates all year round if ASHP doesn’t run at peak time.
20kWh(++?) - as above but more (all) batteries topped up off peak.
The economics seem to work, at the moment, for a battery based system if you can export PV at Octopus rates and then buy back for battery at the off-peak Flux rates but have enough storage to avoid their peak (but some interesting comments in the main solar thread about low temperatures limiting charging rates).
The cost of batteries is a major factor. If they continue on a downward trend then, given the size of battery bank I’d need for the more battery intensive use cases, the best strategy might be to either wait or go small and replace later. Need to run the numbers properly when our ASHP usage pattern has stabilised.
Battery ROI is only improving with smart tariffs, and this is the beauty in smart meters, ASHP, batteries and EV with renewables en masse (home and industrial generation).
Tomato lifestyle is a tariff we just moved to for our ASHP. 5p/kwh 1am to 5am, and a couple of middle rates and then a normal rate during the day.
With battery and PV you can power your entire home at 5p/kwh without much effort. Especially as you charge batteries AND hammer the ashp, dish washer washing machine during those 5p hours....
Tomato lifestyle is a tariff we just moved to for our ASHP. 5p/kwh 1am to 5am, and a couple of middle rates and then a normal rate during the day.
With battery and PV you can power your entire home at 5p/kwh without much effort. Especially as you charge batteries AND hammer the ashp, dish washer washing machine during those 5p hours....
^How is 5kWh of battery going to keep you off peak. Even with your big solar PV array at this time of year it surely cannot sustain a 30kWh daily electricity use (potentially 60kWh with ASHP it seems).
Wouldn't you need at least around 30kWh to be able to stay away form on peak electricity use?
Wouldn't you need at least around 30kWh to be able to stay away form on peak electricity use?
Murph7355 said:
I have an EV, but no V2L capability...but it got me thinking about charging batteries up overnight and then powering the house from them.
Check what your 12V battery charger on your EV is rated for, but you should be able to pull at least 500W direct from the 12V with a pure sine wave inverter and power the boiler/fridge in a power cut. Which is another thing to consider with home storage, do you need power in a grid power cut? We've had increasing number if tree strikes on local power lines.
Andeh1 said:
Especially as you charge batteries AND hammer the ashp, dish washer washing machine during those 5p hours....
Isn't the point of ASHP it had to run essentially 24/7? To hammer in loads of electricity into a battery at the 5-6hr of cheap rates to run an ASHP for the rest of the day will need a 3 phase supply I would have thought.LooneyTunes said:
5kWh - smoothing of PV generation during daylight hours, avoid any peak rates in summer.
10kWh - as above, but avoid peak rates all year round if ASHP doesn’t run at peak time.
20kWh(++?) - as above but more (all) batteries topped up off peak.
By peak I assume you mean evening peak rates (like on Agile or Cosy tariffs) and not the whole day peak.10kWh - as above, but avoid peak rates all year round if ASHP doesn’t run at peak time.
20kWh(++?) - as above but more (all) batteries topped up off peak.
gangzoom said:
^How is 5kWh of battery going to keep you off peak. Even with your big solar PV array at this time of year it surely cannot sustain a 30kWh daily electricity use (potentially 60kWh with ASHP it seems).
Wouldn't you need at least around 30kWh to be able to stay away form on peak electricity use?
I’m looking at peak from the Octopus Flux perspective: 3 rates, off-peak, standard, and peak (a 3 hour early evening window) rather than trying to cover a full 24h period using the cheapest electricity. Wouldn't you need at least around 30kWh to be able to stay away form on peak electricity use?
In the summer, longer daylight hours and generation sees us through that period. Our base load of approx 1kW can also be covered in winter for the duration of the peak period can by saving the battery capacity specifically for that period. The vast majority of our heating/cooking load in the main house is oil, and it should be easy to switch off the ASHP and let it coast for a few hours to avoid that peak. Indeed, it is possible that the ASHP usage may turn out to be much lower than current levels.
Their standard rate isn’t massively different to a general tariff but the cost of this will be offset by export in summer. Basically paying them to time shift production vs usage instead of bearing the capital cost of batteries (for which a proper ROI calc needs to take into account alternative uses of that money).
I still need to run the numbers more fully, and see what is actually needed for the ASHP, before deciding but the price trend for batteries is causing me to hold off before committing to a large bank.
12kWh of storage here. It is workable, but optimum seems to be around one days usage, so here that means I should really have around 24kWh.
Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
Powerwall2 here, so 13.5kwh usable capacity.
Got to consider carefully what makes sense with ROI. Basically you size the battery to the *summer* daytime load - i.e. this means the battery storage will be fully utilised all year round (near enough) by importing grid cheaply overnight. Then in summer you run off the battery and export the solar (at current rates for me anyway) as thats the best VFM.
No point arguably in sizing for winter usage which is 3-5 months of the year (assumed ASHP) because you've then got what, 20KWH of storage for the rest of the year largely sitting idle.
Its a bit counter intuitive, but start from there, then you have to work out if the payback on the 20KWH is worthwhile given its not all year round - I guess it could be for some if the spread between overnight and peak rates is high enough, but pretty sure it isn't at the moment and we've had a historically big delta.
I will admit I've been tempted to look at a 2nd Powerwall 2 while they are still in production so they match, as I think PW3 requires an inverter/gateway upgrade which is alot more cost, but its hard to make it make sense if the ASHP is only pulling for part of the year.
Got to consider carefully what makes sense with ROI. Basically you size the battery to the *summer* daytime load - i.e. this means the battery storage will be fully utilised all year round (near enough) by importing grid cheaply overnight. Then in summer you run off the battery and export the solar (at current rates for me anyway) as thats the best VFM.
No point arguably in sizing for winter usage which is 3-5 months of the year (assumed ASHP) because you've then got what, 20KWH of storage for the rest of the year largely sitting idle.
Its a bit counter intuitive, but start from there, then you have to work out if the payback on the 20KWH is worthwhile given its not all year round - I guess it could be for some if the spread between overnight and peak rates is high enough, but pretty sure it isn't at the moment and we've had a historically big delta.
I will admit I've been tempted to look at a 2nd Powerwall 2 while they are still in production so they match, as I think PW3 requires an inverter/gateway upgrade which is alot more cost, but its hard to make it make sense if the ASHP is only pulling for part of the year.
No ideas for a name said:
12kWh of storage here. It is workable, but optimum seems to be around one days usage, so here that means I should really have around 24kWh.
Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
Yeah a lot of people find themselves with a 3kW inverter limit when a 5-8kW might be needed for peak demand times (heating, cooking, kettle etc)Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
Evanivitch said:
....
Which is another thing to consider with home storage, do you need power in a grid power cut? We've had increasing number if tree strikes on local power lines.
I was thinking that planning to still use grid electricity during cheap hours, this setup also mitigates against power cuts during the day. (It'd pretty much be a normal UPS type setup). Which is another thing to consider with home storage, do you need power in a grid power cut? We've had increasing number if tree strikes on local power lines.
Of course if it went during the night, the batteries wouldn't charge. But whilst we do get cuts (rural) they're not that common (which is asking for bother!).
No ideas for a name said:
12kWh of storage here. It is workable, but optimum seems to be around one days usage, so here that means I should really have around 24kWh.
Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
I was assuming a 32A charger supply, much like my EV one.Also, it isn't as simple as it may first seem. The rate of energy transfer around the system becomes important.
For example, my charger output is 3.5kW, so you can't always fill your batteries at the cheapest rate.
So even assuming I needed a 60kWh-90kWh store (no judging
) it could still charge up off peak pretty much.As others have noticed, prices of batteries are falling, so it might be a case of wait and see.
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