what i should not have done when installing solar

[scottishjohn]

put solar on the new house last year and now having had a winter can say that i didi it wrong

i went for 13.6kw of panels--no problem 

but went for 17kw of batteries -iwa going to go for only 4 batteries in the stack --but when they found they could not fit 30 panels and had to fit only 26 

the deal was i get another battery instead

 

the bottom line is that when its all working on a sunny day then the batteries fill up quick 

 

but in winter  get nothing 

 

with the intelligent octopus tariff 

they pay you same as they charge you for electic 

 ,so once batteries are ful it goes back anyway

 at 27p a unit  and the batteries then discharge between 16.00 and 20,00 hrs at 29p

 

sounds good

but  it will never pay back the cost of  to many batteries

 I am electric only 

so I am always importing  in  badmonths 

 

 so better just to fill smaller batteries sooner   and just take the 27p for the rest of it -the 3p extra form storage will never  pay for the extra batteries

the other thing that happens is it priorities filling batteries ,so like today  I am paying out for import even though its charging batteries -yes iget 3p more when selling back -but not the point

 

If doing it again 

 

yes all the panels the roof will hold .but do not go over the top on batteries ,unless you are dual fuel and then you would store and use it later 

[Beelbeebub]

Useful. 

 

What is your heating system? Storage heaters? Direct electric panels? Heatpump? 

 

I'm currently using my batteries (15kwh) to store E7 electricity and that runs my (gas heated) house pretty much all day on low cost elec - the exception is days when we do alot of washing and there is not much sun, then we end up using a few hours at peak rate. Overall using 95% cheap rate elec. 

 

Am on standard octopus outgoing which was more or less thr same as import (14p cheap rate import, 15p all day export). Unfortunately the export will drop to 12p, but it's not a big deal. 

 

You may be able to get more use from your batteries by switching tariffs and tactics. 

[scottishjohn]

I,m electric only 

heat pump and UFH

Ishould aslo say the house is 400sqm  floor area

Edited 7 hours ago by scottishjohn

[Russdl]

@scottishjohn can you not get a cheaper off peak tariff?

 

We’re all electric. Fill up at 7p export at 15p (soon to be 12p) if there is anything to export. We’ve used very little peak rate electrickery over winter

[JohnMo]

3 hours ago, scottishjohn said:

but in winter  get nothing

That's pretty normal

 

3 hours ago, scottishjohn said:

intelligent octopus tariff

Maybe not the best tariff for winter, Cosy may be better. Fill up at 15p/kWh

 

3 hours ago, scottishjohn said:

3p extra form storage will never  pay for the extra batteries

You may actually make a loss in real terms if you are paying to charge and then discharging with round trip losses.

 

3 hours ago, scottishjohn said:

do not go over the top on batteries ,unless you are dual fuel and then you would store and use it later

Not sure about that, its more about being on the correct tariff. My electric cost to buy is currently 15p, excess PV I get 15p. I never charge battery to get paid for discharging only, only export excess energy from PV.

[Oz07]

So much of the case for buying all these expensive batteries has always seemed based on gimmicky tariffs to me.

[ProDave]

I might be looking as some battery storage in the future but if I do it must be cheap and will ONLY be to store surplus solar PV for later, I am not interested in importing / exporting at different rates hoping to turn a profit.

[Beelbeebub]

1 hour ago, Oz07 said:

So much of the case for buying all these expensive batteries has always seemed based on gimmicky tariffs to me.

Mine is based on the decidedly old school economy 7 tariff that's been around forever and will prob still be around for some time to come given the number of people on all electric heating with no heatpump eg all electric flats. 

 

My batteries were sized to cover 90% of my days. 

 

As the export rate falls I'll have to get smarter about only filling the battery as much as I need but for now (this winter) fill up at night on 14p electric seems to be the best strategy. 

[Russdl]

2 hours ago, ProDave said:

 

I might be looking as some battery storage in the future but if I do it must be cheap and will ONLY be to store surplus solar PV for later, I am not interested in importing / exporting at different rates hoping to turn a profit.

 

Our wasn’t necessarily cheap (but thanks to info from @JohnMo massively cheaper than the first quote we got). 
 

The tariff dictates our usage, currently 15p export and 7p/29.14p import.
 

We’d be mad to use our solar when the batteries take us through the day with ease and the off peak tariff heats the house/water does the dishes/washing charges the car etc etc. 

 

Sure the tariff will change, and is about to, and working out ROI would be tricky, too many variables etc but our annual usage at peak rate would be around £2500/year.

 

Last year we paid minus £400.
 

Which is nice.