The reality of PV solar panels
and battery storage
to be reading about at the moment, is how battery storage will
plug the gap from generation to consumption and make us all very
rich or at least smug. I hear stories from neighbours with PV
who are being targeted by battery storage sales people promising
all sorts of claims.
But what does a battery do and
how does it behave?
the difference between Lead Acid and the becoming cheaper Lithium
battery. The difference seems to be efficiency, cost and the
availability of energy. My main lesson has been the last bit. If you
buy a 6.4 kwh Tesla Power wall with all its hype and nice packaging.
You don't actually get 6.4 kwh but more like 75% of this because a
battery never truly empties. A lead acid is more like 50% of the
capacity is available. On the Power wall the 6.4 kwh actually means
4.7 kwh in available energy. You also loose 7.5% in efficiency in
terms of what you put in vs what you get out (Tesla efficiency rating,
I will leave that out for now)
Will it pay for itself in a
reasonable time frame or should I keep looking at what to do with the
excess power in summer when I don't need it for heat or evening
electricity and so on. I have a 4kw PV system in the back garden and
then I realised I did not understand my daily, monthly and seasonal
use of energy or my energy generation characteristics. I then spent a
couple of evenings modelling, measuring and understanding what I make
in PV energy and how much I need and when do I need it?
The truth of battery storage -
facts and figures
Typical house using the national average of 3800 kWh per year and
solar PV system generating 3500 kWh per year.
- Price of electricity per kWh is £0.12 pence.
Energy Saving Trust quotes an average saving of £125.00 per year for
a typical home, they also quote £0.145 pence per kWh.
divided by £0.145 = 862 kWh used in the home from the generated solar
PV system, or a saving of 23% of the 3,800 kWh.
- So what else can you save by
installing a battery storage?
at it this way, if you use 3,800 kWh per year you use on average 10.41
kWh per day, so it's only possible to save 10.41 kWh per day.
data downloaded from SMA inverters the
- Real PV facts, real figures
KW solar PV generating on south facing roof 3000 kWh per year.
price of electric per kW, £0.13 pence.
PV savings without Battery storage according to the Energy saving
trust (EST) is £125.00.
EST quote £0.145 price per kW so £125 divided by £0.145 is 862
kWh per year.
Storage savings over 300 days @ 5KW (size of battery bank) 1500
kWh @ £0.13p = £195.00.
payment if available 3000 kWh @ 4.3 p = £129.00.
payments 3000/2 x 4.86p = £72.90.
total savings for year 1 = £125.00 + £195.00 + £129.00 + £72.90
lifespan is ten years or 3,000 cycles.
Important technical details to
PV systems with battery storage may not be eligible for the FIT's
payments if the battery is installed before the generation meter.
benefit of the Solax inverter charger is in the event of a power cut
the inverter can power the home up to a maximum load of 2kW, a manual
change over switch is required to isolate the incoming supply and an
external earth rod is required to earth the property.
is important to point out that PV solar panels installed in different
locations will give different output figures. However, as these
figures were produced in Lincolnshire and this is a central location
within the UK, I would use them as an average with greater figures
occurring the more southerly your location and lesser figures when
your location is more northerly.
are brilliant battery storage systems on the UK market that are tried
and tested around the world. PV solar panels working alongside battery
storage devices and even EV charging are an option to consider in
addition to the current incentives for solar panels. A good solar
installer will be able to advise you on both types of system.
there are sharks in our industry as with any other, but clear facts
will always trump 'bullshit' sales when time is taken to research
your options properly. Remember sharks feed off ignorance!
solar PV and battery storage systems are on the rise and it will
remain a viable option for many when bought at the right price from
the right installer.