Solar Power and an economy 7 meter -should I get a battery, how to use it please?

krissy08

Hello all,
I got solar panels 7 years ago because I love the idea of being green but I don't really understand it. I have 28 of them generating approx 3750kwh per year.
Here is a photo of my set up attached. My questions are;
I have an economy 7 meter, for 7 years I have asked to be on a flat rate instead as I read it was more efficient - I don't believe I have a storage battery.
 I am a heavy day user , having worked from home all these years and use very little at night. 30 vs 6 KW per day respectively according to my energy supplier.
Any advice please...
Should I get batteries top store economy 7 power ?
While on the normal pv system I have now (please see photo) should I use revert to the dual rate economy 7 and use more night energy ?

thank you for your patience

Reed_Richards

I see no sign of a battery in the picture.  You might not be able to add a battery without losing your FIT payments as you will have signed an undertaking not to change the configuration of your solar PV system.  Try the Green and Ethical  board for more advice: https://forums.moneysavingexpert.com/categories/green-ethical-moneysaving

QrizB

There's a thread here where someone bought batteries to make better use of their E7:

https://forums.moneysavingexpert.com/discussion/6348424/economy-7-battery-storage/p1

In their case, the financial benefit wasn't at all clear (although there arew other non-financial benefits, eg. a degree of protection against power cuts). Batteries might work out better for you as, for at least half the year, you'll benefit from storing your surplus solar electricity.

krissy08 said:

I am a heavy day user , having worked from home all these years and use very little at night. 30 vs 6 KW per day respectively according to my energy supplier.
Any advice please...

Do you have a set of day & night meter readings from about a year ago, and another recent set (or you could read them today)? We can see what your annual day/night split is.

krissy08

Hi- Thank you as always QrizB, apologies for the late reply- it's been a busy week.
I have these meter readings from 2021;

Customer reading

DAY R 7th April 2021 63577

NIGHT R 7th April 2021 12267

for 2022;

1st Apr 2022 Energy Used (Night) 9th Mar 2022 1st Apr 2022.     Energy Used (Day) Standing Charge

NIGHT Customer reading; R 12501.0   

 DAY Customer reading; R 65058.0 

Does this help?
I really appreciate your help with this.

QrizB

Thanks for the readings.

Over that almost-a-year you've used 234kWh of night electricity, and 1481kWh of day energy.

That's roughly 14% on the night rate, such a small amount that you will almost certainly be better off on a single-rate electrity tariff (at least while you don't have a battery).

If you were to buy a battery (and the thread I linked to earlier gives an idea of the costs) you might be able to get through 6 months of the year without buying much electricity from the grid, asnd the other 6 months you could buy E7 night rate. But battery prices have risen along with everything else recently, so it might not pay for itself for a decade or more.

ispookie666

Reed_Richards said:

I see no sign of a battery in the picture.  You might not be able to add a battery without losing your FIT payments as you will have signed an undertaking not to change the configuration of your solar PV system.  Try the Green and Ethical  board for more advice: https://forums.moneysavingexpert.com/categories/green-ethical-moneysaving

Can the batteries not be installed as a standalone unit, so that there is not change in configuration?  

[Deleted User]

It is worth spending a bit of time looking at the need for DNO approval for a battery. Batteries are treated as potential generators as far as the Grid is concerned. For a fee, the DNO will review the proposed installation and the local Grid infrastructure and it may impose a site export limit. Clearly, any AC battery needs to be installed downstream of the solar generation meter.

As I understand it, the above can be avoided if a DC battery is installed on the solar panel side of the inverter. However, the downside of going down the DC battery route is no charging from the grid.

https://www.deegesolar.co.uk/ac_coupling_vs_dc_coupling_solar_battery_storage/

QrizB

Dolor said:

Clearly, any AC battery needs to be installed downstream of the solar generation meter.

Agreed, and all the guidance says the solar PV system (including its generation meter) should be installed on its own dedicated circuit from the consumer unit, with an AC-coupled battery on a separate dedicated circuit.

Reed_Richards

[Deleted User] said:

However, the downside of going down the DC battery route is no charging from the grid.

I have a DC battery and I can charge from the grid if I want to (although since I am stuck on a single rate tariff there is no point).  On rare occasions, for example if my battery charge gets down to 5% after prolonged cloud in winter, the inverter will charge it up from the grid; it seems to target 15% charge.  The reason this is possible is that my generation meter gives a net (Out - In) reading by default.  I submit the net reading for FIT payments. 

markin

What is your yearly power Bill? Its worth changing to a single rate, But im not sure its worth spending £3.5-5K to make the grid use less.

Average import is 4.7kwh a day.