Is solar battery storage worth it?

NedS

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

Exactly - gas is priced at around 6p per kWh and excess solar is worth 15p per kWh (assuming SEG of 15p), so you'd be much better off exporting excess solar at 15p and then paying 6p to heat your water as required with gas.

Martyn1981

NedS said:

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

Exactly - gas is priced at around 6p per kWh and excess solar is worth 15p per kWh (assuming SEG of 15p), so you'd be much better off exporting excess solar at 15p and then paying 6p to heat your water as required with gas.

Or, if you have cheap rate leccy, heat the water with leccy at 7p, which might be cleaner than gas, and possibly cheaper (or at least similar to) than 6p gas, unless the boiler is running extremely efficiently.

JKenH

NedS said:

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

Exactly - gas is priced at around 6p per kWh and excess solar is worth 15p per kWh (assuming SEG of 15p), so you'd be much better off exporting excess solar at 15p and then paying 6p to heat your water as required with gas.

I think this reflects the reality of how most people think. I could use electricity from my domestic solar installation to heat my water but it is cheaper to burn gas (or oil in my particular case) so I do that and export my electricity to the grid. Collectively, that means we need less generation from wind farms so they are paid for the not producing what we are sending to the grid. 

Electricity suppliers, e.g. Octopus, by their pricing policies are actively encouraging us to do this. I probably receive benefit of in the region of £1k per year to export electricity, the majority of which is not required by the grid at the times when I am able to export. Round about lunchtime on Thursday I was exporting 4.5kw and the spot price was £-19/MWh. Imagine the impact of 1m or more homes with solar doing the same - the cost is £675,000/hour paid to consumers and £85,500 income foregone on the spot market. On top of which is 4.5 GWh of constraint payments. 

Who ultimately picks up the tab for this? The electricity consumer. August has been a great month for those of us with solar panels able to export but not for the average electricity consumer.

Had we not been incentivised to export rather than self consume, those of us with immersion heaters could have avoided huge amounts of CO2 emissions from unnecessarily burning fossil fuels to heat our DHW.

Let’s be honest, though, most of us take the attitude that we are quids in exporting, so let’s take these export rates while we can get them and not worry too much about the CO2 we could be saving by heating our DHW. Yes, we are all concerned about CO2 until saving it hurts our pocket. 

I am not having a go at anyone, just pointing out it’s human nature to put one’s own and, we would say, our family’s interests, ahead of society as a whole. Yes there are those who have taken that extra step and ditched their gas boilers but for most of us we need someone or something to make it worth our while to do the right thing. 

EcoScruples

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

This is absolutely correct and also if you don’t use all of the hot water you’ll have essentially waisted that saving as you’ll lose that heat overnight.
selling excess to the grid has the biggest instant impact.

And the greenest.

Magnitio

JKenH said:

NedS said:

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

Exactly - gas is priced at around 6p per kWh and excess solar is worth 15p per kWh (assuming SEG of 15p), so you'd be much better off exporting excess solar at 15p and then paying 6p to heat your water as required with gas.

I think this reflects the reality of how most people think. I could use electricity from my domestic solar installation to heat my water but it is cheaper to burn gas (or oil in my particular case) so I do that and export my electricity to the grid. Collectively, that means we need less generation from wind farms so they are paid for the not producing what we are sending to the grid. 

Electricity suppliers, e.g. Octopus, by their pricing policies are actively encouraging us to do this. I probably receive benefit of in the region of £1k per year to export electricity, the majority of which is not required by the grid at the times when I am able to export. Round about lunchtime on Thursday I was exporting 4.5kw and the spot price was £-19/MWh. Imagine the impact of 1m or more homes with solar doing the same - the cost is £675,000/hour paid to consumers and £85,500 income foregone on the spot market. On top of which is 4.5 GWh of constraint payments. 

Who ultimately picks up the tab for this? The electricity consumer. August has been a great month for those of us with solar panels able to export but not for the average electricity consumer.

Had we not been incentivised to export rather than self consume, those of us with immersion heaters could have avoided huge amounts of CO2 emissions from unnecessarily burning fossil fuels to heat our DHW.

Let’s be honest, though, most of us take the attitude that we are quids in exporting, so let’s take these export rates while we can get them and not worry too much about the CO2 we could be saving by heating our DHW. Yes, we are all concerned about CO2 until saving it hurts our pocket. 

I am not having a go at anyone, just pointing out it’s human nature to put one’s own and, we would say, our family’s interests, ahead of society as a whole. Yes there are those who have taken that extra step and ditched their gas boilers but for most of us we need someone or something to make it worth our while to do the right thing. 

I don't think it's a good idea to base an argument around last Thursday lunchtime. August has been both sunny and windy, so renewable generation has been good. It's not been a typical month, however, for the vast majority of the year, exporting excess solar reduces the burning of stuff at power stations and that is a good thing. People are also being incentivised to use electricity when there is a surplus. Additional storage is being added to the grid to mop up the excess and release it when there is higher demand. It's not possible to transition the grid to renewables in one go, so there will be times of over/under supply. 
As individuals, unless we monitor in detail the pricing fluctuations and weather conditions, we aren't going to do what is best for the grid/environment every hour of every day. I do make some decisions on energy usage based on forecasts e.g. car charging on windy nights, and I'm sure many others do similar. 

1961Nick

Martyn1981 said:

NedS said:

Qyburn said:

PDoffwiththeBBC said:

Hi,

    A much cheaper way of "storing" your excess solar output is to use an immersion diverter. 

Surely that only makes economic sense if your normal water heating costs you more than 15p/kWh. Otherwise you're better "storing" you excess in the grid.

Exactly - gas is priced at around 6p per kWh and excess solar is worth 15p per kWh (assuming SEG of 15p), so you'd be much better off exporting excess solar at 15p and then paying 6p to heat your water as required with gas.

Or, if you have cheap rate leccy, heat the water with leccy at 7p, which might be cleaner than gas, and possibly cheaper (or at least similar to) than 6p gas, unless the boiler is running extremely efficiently.

During summer the boiler is unlikely to achieve anything above 75% efficiency on a DHW only cycle - The time it takes to start condensing & run efficiently is a significant part of the cycle & there's a lot of hot water wasted in the pipework & heat exchanger when it's finished.

1961Nick

My original 4 Pylontechs are nearly 6 years old & have a SOH of 94.79% after 1498 cycles.

Talk of a 10-15 year lifespan seems very pessimistic especially as the degradation wasn't linear & most of it occurred in the first 12 months.

Freepost

Is solar battery storage worth it?

I have a 3.8kw solar PV system, installed Nov'2011, and I had pondered the installation of batteries for the past years but I seem to have a mental block on justifying the addition of batteries to the system. 

Prior to the installation of Solar PV my annual electricity consumption was ~ 4800kWh. Since the installation my average consumption has reduced to 2800kWh. For me this indicates that the system has saved me 2000kWh/year. 

The solar PV system is generating ~3200kWh/year and from the above, I am using ~2000kWh with the other 1200kWh being lost to the grid. Now if I install batteries then I can store and use this 1200kWh, perhaps nearer a 1000kWh with incurred loses, and that's money saved but what will I save? The cost of a kWh from Octopus is approx. 26p which times a 1000kWh = £260.00/a, would this saving justify the cost of installing battery storage? I don't think it does, remembering that my system was installed in 2011 and that I am only guaranteed the FiT for 25years which means that I only have 12 years left and 12 x £260.00 = £3120.00. 

Can somebody please check my maths, I may have done something stupid, I also fully understand that my system will not stop working in 12years time but the FiT does.

Thanks

F.

Qyburn

Freepost said:

Can somebody please check my maths, 

The missing bit is export credits. On metered export you could be receiving 1200 x 15p = £180.00 per year. But I don't know what you currently receive for deemed export, nor whether you'd still retain that payment after adding a battery.

Qyburn

JKenH said:

I think this reflects the reality of how most people think. I could use electricity from my domestic solar installation to heat my water but it is cheaper to burn gas (or oil in my particular case) so I do that and export my electricity to the grid. Collectively, that means we need less generation from wind farms so they are paid for the not producing what we are sending to the grid. 

I'd have some sympathy for that view if even a tiny slice of the renewable energy industry was run on such altruistic lines. But consider even at the farm level there are landowners with two or three 900kW turbines, receiving 28p/kWh FIT generation payment on top of the wholesale value of their electricity. You don't see them volunteering to shut off generation when it's not needed.