Batteries

powerful_Rogue

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

QrizB

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

powerful_Rogue

QrizB said:

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

Many thanks for your reply. I'm getting solar installed at the end of October.

A good way of looking at things. On ECO7 my day rate will be 43pKwH, so using that rough guide would work out at a saving of £161 a year, or a 14 year payback period. That makes it seem a bit more interesting!

uk1

powerful_Rogue said:

QrizB said:

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

Many thanks for your reply. I'm getting solar installed at the end of October.

A good way of looking at things. On ECO7 my day rate will be 43pKwH, so using that rough guide would work out at a saving of £161 a year, or a 14 year payback period. That makes it seem a bit more interesting!

It does seem to my extremely limited understanding ie purely instinct that a consideration that I’m choosing to factor in is an increasing number of utility suppliers possibly offering “realistic” off peak power options.  Also by over-dosing on battery you are hedging against alarming future price increases.  I’d be using twice as much kwh in the very months when there is very little power from the array.  So to my mind a way of hedging that is by having sufficient power stored  in batteries to give me a days supply but charged off-peak.  With the increasing life of batteries and increasing power costs, it’s my instinct that whilst payback isn’t good initially it might turn out shorter than we think. 

But what do I know!

powerful_Rogue

uk1 said:

powerful_Rogue said:

QrizB said:

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

Many thanks for your reply. I'm getting solar installed at the end of October.

A good way of looking at things. On ECO7 my day rate will be 43pKwH, so using that rough guide would work out at a saving of £161 a year, or a 14 year payback period. That makes it seem a bit more interesting!

It does seem to my extremely limited understanding ie purely instinct that a consideration that I’m choosing to factor in is an increasing number of utility suppliers possibly offering “realistic” off peak power options.  Also by over-dosing on battery you are hedging against alarming future price increases.  I’d be using twice as much kwh in the very months when there is very little power from the array.  So to my mind a way of hedging that is by having sufficient power stored  in batteries to give me a days supply but charged off-peak.  With the increasing life of batteries and increasing power costs, it’s my instinct that whilst payback isn’t good initially it might turn out shorter than we think. 

But what do I know!

Exactly my thinking. Charging them both up for £2.08 off peak and then not having to worry at all during the winter days. If I wasn't going to rely on Octopus export, I would have tried to switch to EDF where I could charge them for 97p!

Just purchased a heat pump tumble dryer and a new energy efficient tumble dryer, both which have timers so can set them to also come on during the off peak.

Next was my TV, however i've had it for 13 years, still works fine, but is quite energy hungry. Having a battery will help with that!

uk1

powerful_Rogue said:

uk1 said:

powerful_Rogue said:

QrizB said:

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

Many thanks for your reply. I'm getting solar installed at the end of October.

A good way of looking at things. On ECO7 my day rate will be 43pKwH, so using that rough guide would work out at a saving of £161 a year, or a 14 year payback period. That makes it seem a bit more interesting!

It does seem to my extremely limited understanding ie purely instinct that a consideration that I’m choosing to factor in is an increasing number of utility suppliers possibly offering “realistic” off peak power options.  Also by over-dosing on battery you are hedging against alarming future price increases.  I’d be using twice as much kwh in the very months when there is very little power from the array.  So to my mind a way of hedging that is by having sufficient power stored  in batteries to give me a days supply but charged off-peak.  With the increasing life of batteries and increasing power costs, it’s my instinct that whilst payback isn’t good initially it might turn out shorter than we think. 

But what do I know!

Exactly my thinking. Charging them both up for £2.08 off peak and then not having to worry at all during the winter days. If I wasn't going to rely on Octopus export, I would have tried to switch to EDF where I could charge them for 97p!

Just purchased a heat pump tumble dryer and a new energy efficient tumble dryer, both which have timers so can set them to also come on during the off peak.

Next was my TV, however i've had it for 13 years, still works fine, but is quite energy hungry. Having a battery will help with that!

That is a relief to read.  I thought that I was going barmy and feeling extremely lonely!

To me, the investment in solar and a rather extravagant battery store is impossible to make any sensible payback calculations today and from my perspective I’d rather compare the capital cost with what would I get from using the same cash in an ISA or high interest account.  

If I buy reasonably well - and I have had a couple of extremely odd quotes - then the increase in energy costs gives a degree of protection to the capital cost invested and included in my house value if I were to sell my home, which I do not plan to do.  So with an excessive battery store I would be comparing the future power cost saved as a percent of the total cost and comparing that with my ISA/other interest rates.  And if I were to save say £4k per year in a couple of years time on say a £15k investment doesn’t sound too bad a choice to me to get on with now.  Yes, I could save a little now by downsizing the battery store and wait and upgrade later but I tend to get  on with it.   I think that more people spend time regretting not spending enough than the nuber who regret spending a bit too much. 

ispookie666

I have 2*8.2KWh Givenergy battery which will do roughly 24 hrs for us(without any sun) and have a few more KWh spare for backup.  This becomes a lot more useful when you have a few dull days and the battery keeps you going without grid draw.  

QrizB

powerful_Rogue said:

QrizB said:

powerful_Rogue said:

Jumping into this thread, i've got a system being installed  next month including a 6.5kWh battery.

Looking at previously months, we use on average 10kWh a day. I've been told I can have a second 6.5kWh battery installed at the same time for £2300.

My plan during the the autumn/winter is to charge up overnight as on Eco7 at 16p kWh. Day time useage would be 43pkWh.

Just trying to work out whether it's worth getting the extra battery, espeically as i'll be saving on VAT.

You have (or are getting) solar too? In which case, the number of days in the year where you'll need more than the 6kWh or so of storage that your battery offers will be fairly small. Let's say a quarter of them, 90 days a year.

And let's say that on those 90 days you'll need an average of 3kWh extra. That's 270kWh per year that you'll be able to buy for (at current prices) 27p/kWh less, a saving (ignoring losses) of £73 per year and a 32-year payback period.

Financially, I don't think an extra battery makes much sense at that price.

Many thanks for your reply. I'm getting solar installed at the end of October.

A good way of looking at things. On ECO7 my day rate will be 43pKwH, so using that rough guide would work out at a saving of £161 a year, or a 14 year payback period. That makes it seem a bit more interesting!

I'm not following your maths, sorry. We might be doing different calculations. Here's how mine went:

• You use 10kWh a day, every day.
• You've already budgeted for a 6kWh battery.
• The maximum same-day benefit from another battery is 4kWh, but you'll only need that in the winter quarter - and you won't need all 4kWh every day, so I've guesstimated an average of 3kWh.
• You'll buy those 3kWh for 16p/kWh instead of 43p/kWh, a saving of 27p/kWh - so, for 3kWh, a 81p saving.
• Multiplied by 90 days makes £73 of benefit a year from the extra battery.
• The extra battery is £2300, and dividing that by £73/yr makes 32 years.
  

Missing from my calculations is any allowance for conversion losses, or for the inevitable fall in retail electricity prices in the medium term.

How did you manage to calculate double the saving and half the payback period?

Solarchaser

Around 12kwh should be best roi as your usage is similar to mine.
If you want a cover all, around 24kwh will be what you need, but won't be helpful on roi calculations. 

I have 20kwh usable btw, and have had for a couple of years 

uk1

Solarchaser said:

Around 12kwh should be best roi as your usage is similar to mine.
If you want a cover all, around 24kwh will be what you need, but won't be helpful on roi calculations. 

I have 20kwh usable btw, and have had for a couple of years 

Thanks.  I currently have in mind 6 x 3.5 making 21 in total.