Views on battery quote please

Rheumatoid

Exiled_Tyke said:

My 6.3 kWh Solax battery cost me £3750 two years ago.   The price worked out the same with or without a couple of extra solar panels. So I got these fitted with micro inverters which made the whole lot VAT free.  (Otherwise it would have been pretty much the same price just for the battery with VAT).   I"m very happy with it and although we are not heavy users here, ideally I would have something a little bigger.  

So you don't think 6.3 is quite enough for your 4kwh system and you pattern of usage? The kids are in the process of leaving so there will be 2 of us in a 4 bed detached with one at work (for the next 2 years) and one retired - although I am not here much in the day if I have my way :-)

Solarchaser

I'd say that since you are only buying 3000kwh a year, the 4.8/4.3 is likely good enough.

Plus the pylontech batteries are pretty widely available even on ebay and so if you wanted another you could just but one for £7-800 and clip it on yourself,  versus the £1000+ they want for adding another in, its a very simple and modular system.

Exiled_Tyke

Solarchaser said:

I'd say that since you are only buying 3000kwh a year, the 4.8/4.3 is likely good enough.

Plus the pylontech batteries are pretty widely available even on ebay and so if you wanted another you could just but one for £7-800 and clip it on yourself,  versus the £1000+ they want for adding another in, its a very simple and modular system.

Frankly no I don't think it's enough. 3000kWh a year is 8kWh a day. Obviously this isn't evenly spread throughout the year and it's likely that winter import will be much higher than summer.   My personal situation is that there are two us, both working from home.  For most of the year I run the battery down to it's minimum every day.  At this time of year I top up overnight using Octopus Go rates.  If I have the oven on for the evening meal (which is most evenings!) then currently I run out of battery power well before the cheap rates cut in at half past midnight.  Of course household has a different useage pattern but at an average import (not useage) of 8kWh a day (with more in winter and less in summer)  then I'd be looking ideally for 8kWh of useable capacity. 

Today is a good case study. A sunny October day and I generated just about spot on 8kWh.  The battery got back to full (well 95%) mid-afternoon.  So we did have enough sun to fill a larger battery and it would be used. 

Rheumatoid

Exiled_Tyke said:

Solarchaser said:

I'd say that since you are only buying 3000kwh a year, the 4.8/4.3 is likely good enough.

Plus the pylontech batteries are pretty widely available even on ebay and so if you wanted another you could just but one for £7-800 and clip it on yourself,  versus the £1000+ they want for adding another in, its a very simple and modular system.

Frankly no I don't think it's enough. 3000kWh a year is 8kWh a day. Obviously this isn't evenly spread throughout the year and it's likely that winter import will be much higher than summer.   My personal situation is that there are two us, both working from home.  For most of the year I run the battery down to it's minimum every day.  At this time of year I top up overnight using Octopus Go rates.  If I have the oven on for the evening meal (which is most evenings!) then currently I run out of battery power well before the cheap rates cut in at half past midnight.  Of course household has a different useage pattern but at an average import (not useage) of 8kWh a day (with more in winter and less in summer)  then I'd be looking ideally for 8kWh of useable capacity. 

Thanks. That's useful. I'm tempted to go with 6.5 and see how it goes if it is relatively easy to add another 2,16 later. But might just bite the bullet and go with 8.6 and be done with it.

Petriix

Rheumatoid said:

Exiled_Tyke said:

Solarchaser said:

I'd say that since you are only buying 3000kwh a year, the 4.8/4.3 is likely good enough.

Plus the pylontech batteries are pretty widely available even on ebay and so if you wanted another you could just but one for £7-800 and clip it on yourself,  versus the £1000+ they want for adding another in, its a very simple and modular system.

Frankly no I don't think it's enough. 3000kWh a year is 8kWh a day. Obviously this isn't evenly spread throughout the year and it's likely that winter import will be much higher than summer.   My personal situation is that there are two us, both working from home.  For most of the year I run the battery down to it's minimum every day.  At this time of year I top up overnight using Octopus Go rates.  If I have the oven on for the evening meal (which is most evenings!) then currently I run out of battery power well before the cheap rates cut in at half past midnight.  Of course household has a different useage pattern but at an average import (not useage) of 8kWh a day (with more in winter and less in summer)  then I'd be looking ideally for 8kWh of useable capacity. 

Thanks. That's useful. I'm tempted to go with 6.5 and see how it goes if it is relatively easy to add another 2,16 later. But might just bite the bullet and go with 8.6 and be done with it.

While I've been doing my maths I've factored in that I will shift a proportion of my load to the cheap 5p period on Go. I'll definitely be able to charge the EV then but it won't be too hard to run the dryer (a significant winter consumption) in that period as well. So while I average around 3000kWh in imports over the year, I think the battery would only need to cover about 5kWh per day when there's no generation.

When there is some variable surplus which would have previously been hard to use (a partly cloudy day) I would be able to partially cycle the battery multiple times. I could charge to 75% full overnight then do a load of washing and run the dishwasher, part solar powered and part battery powered before letting the battery charge a bit in advance of the evening usage. It's only in the depths of winter or in a prolonged dark period that it would become challenging. But I can space out when certain appliances are run.

Solarchaser

Exiled_Tyke said:

Solarchaser said:

I'd say that since you are only buying 3000kwh a year, the 4.8/4.3 is likely good enough.

Plus the pylontech batteries are pretty widely available even on ebay and so if you wanted another you could just but one for £7-800 and clip it on yourself,  versus the £1000+ they want for adding another in, its a very simple and modular system.

Frankly no I don't think it's enough. 3000kWh a year is 8kWh a day. Obviously this isn't evenly spread throughout the year and it's likely that winter import will be much higher than summer.   My personal situation is that there are two us, both working from home.  For most of the year I run the battery down to it's minimum every day.  At this time of year I top up overnight using Octopus Go rates.  If I have the oven on for the evening meal (which is most evenings!) then currently I run out of battery power well before the cheap rates cut in at half past midnight.  Of course household has a different useage pattern but at an average import (not useage) of 8kWh a day (with more in winter and less in summer)  then I'd be looking ideally for 8kWh of useable capacity. 

Today is a good case study. A sunny October day and I generated just about spot on 8kWh.  The battery got back to full (well 95%) mid-afternoon.  So we did have enough sun to fill a larger battery and it would be used. 

Frankly, just because you use it, doesn't mean everyone else will.
As you touched in yourself,  you use more in winter and less in summer.
If you are looking for a decent roi you need to cycle every day.

And if you are using 3000kwh a year, that means realistically less than 1000 during the brightest 6 months, so you won't cycle that larger battery and so your roi will be much longer.

Today it's one of the 4 bright days over the last 20, that makes it a bad case study as its the outlier not the norm. 

However the point remains that the company is charging over a grand for a £7-800 battery, so still cheaper buying elsewhere and clipping on if you don't care about roi.

I'd suggest you move your recharge period to 8:30pm start as I have with go faster, that means you are covering less of the evening with batteries, and more of the night, this works well to catch evening snacks etc

arty688

I wouldn't recommend shifting tariffs ATM though.

2nd_time_buyer

My hunch is that a lot of the benefit from having a battery is being able to deliver required power throughout the day.

Most appliances (e.g. washing machines, dishwashers, tumble dryers, ovens) cycle between high power (2-3kw) and low power (<200w) throughout the cycle. With the vast majority of the energy consumed in the high power phases. In practice, these high power "heating" appliances make up the majority of consumption for most people.

Without a battery, a typical 4kw system, might only be able to deliver 3kw for a small proportion of the hours in a year (I am guessing less than 5%).

So even a small battery will help a lot n meeting demand. The Pylontech batteries have an output of 1.2kw per module. Therefore with 2 of those it should be possible to meet the majority of intra-day demand. 

... beyond this, I suspect, we will be in the realms of diminishing returns.

2nd_time_buyer

... having an electric car is a bit of a game changer. 

In effect you have a massive battery (>30kwh) which will probably dwarf any home battery. Depending on how you use your car, it could make a big home battery largely redundant.

Petriix

2nd_time_buyer said:

... having an electric car is a bit of a game changer. 

In effect you have a massive battery (>30kwh) which will probably dwarf any home battery. Depending on how you use your car, it could make a big home battery largely redundant.

Unfortunately it's not possible to retrieve the energy from the EV to use in the house (yet). Next generation EVs are coming with V2L - a 240v socket - so you could run some appliances, but V2H is still some way off. Even the current V2G trial units don't seem to have a way for the end user to access the power, let alone an automated system that reads the net import/export and adjusts accordingly.

A home battery will actually work really well in conjunction with an EV. At this time of year I regularly have a ~ 1kW surplus. If I want to charge the car then I have to import the difference to make up the minimum 1.4kW. With a battery I could charge the car for a couple of hours and let the home battery make up the difference, then unplug the car and let the home battery recharge again. Even a really small battery would facilitate that (with shorter times).