Since moving and having solar energy and not being able currently to take advantage of an export tariff I’ve been looking at the battery storage options. Funnily enough since I’ve been talking about them at home at least 2 have come up in my Facebook ads and it’s got me thinking about real life usage and how effective they’ll be. I have 8 300 watt panels which today have generated around 2500w sporadically throughout the day. I know we’re not in to the summer months yet and so my system is rated 2400w so clearly today is about as good as it gets. The MOIXA and Tesla systems are a world apart with regards to storage and price however I cant see them storing enough energy even on a day like today to run the house in the evenings which is essentially when I’ll need it the most. I know everyone is different and usage and needs change but I’m guessing most of us are at work all day and need the power from 5 onwards to cook, lights etc.
Anyone own a storage system and can comment about state of charge, how long they’ll power the house for and in short are they worth it or just a gimmick?
FFF
watching in interest. . . . last I heard battery storage units are expensive and not great for the environment either (materials, emissions created when making them, disposal of nasty substances). I remember at work they had a bank of batteries for our DC which lasted about 15mins - just enough to shutdown systems without crashing. Different scale to a private house of course.
So are batteries worth it? This depends on how you value autonomy and the maximisation of your self generated solar energy.
You don’t have a huge PV system and so as rules of thumb - your 2.4kWpk system will generate c 2100 kWh per year . Of this if you are at work and not massively setting everything to come on in the sunny hours - you will probably export around 75% of this (1600 kWh) if you had an appropriately sized battery you would use more of your own energy and thus only export 25% ish of what you generated. This means you would input around 1000 kWh less per year so around £150 pa benefit.
These calcs ignore any FiT revenue as that is unaffected by having a battery. HTH
Hi, I have a 5.2kv PV system connected to a Tesla 2 Powerwall, to run a 5 bedroom house, 3 people, and oil fired central heating. Our daily electric usage is approx 14kw per day.
The reason for going for the Tesla, was it has the highest storage capacity (13.5kw) for the lowest price, it also can deliver higher discharge rate (about 3.5Kw) than most other battery systems. Add in the 10 year warranty, Tesla support and teslas web enabled monitoring and it was a no brainier (for me).
In 2019 since installation (end July) we effectively paid nothing for our electricity.
In Jan 2020, we generated 139kw (crappy), of which 65kw was stored and consumed by us. We imported a further 332kw from the grid.
in Feb, we generated 219kw (getting better despite the weather), of which 118kw was stored and later consumed. The amount we imported from the Grid reduced to 208kw.
Today (real-time data), we have generated 20.5kw, we have used 3.3kw from the Tesla, and have used 0.2kw from the grid. The Tesla (which was pretty much empty this morning), is now sitting at 84% capacity (so is holding about 10kw) for further use, as soon as the PV stops generating.
A couple of points - the Tesla 2 does not provide “fail-over” in the event of power cut, but it is an option on Powerwall 3. You cannot use the grid electricity to charge the battery. I looked at using Economy 7 to top up the Tesla up at night, but it was a non-starter. The Tesla is very slim and waterproof hence can be bolted to the side of a house if you wish. We have ours in the Garage.
As for it being a gimmick - No, but only if you are exporting Electricity. If so, without a battery, then at best you are getting 3.5p per Kw, which you then buy back at approx 14.5p per KW as soon as your PV stops generating. No good economics.
As for it being cost effective - it’s depends on your usage and the size of your PV, and what electricity will cost in future, but as I was exporting lots of energy during the day and buying it back again at night, hence thought it was worth a punt. If I could have consumed all the energy I was generating during the day, then most likely not. That said it’s very cool technology and will make a EV or Plug In Hybrid much more affordable.
Plus, irrespective of the money, it’s nice I am doing my bit to help the planet.
If you have any questions let me know, as I am a huge fan.
If I was you, I would look at how much your system exported during April to Oct, what your daily usage is, how much you are paying for your electric and go from there.
Whoever does not know how to hit the nail on the head should be asked not to hit it at all.
Friedrich Nietzsche
So in a very small nutshell, if a system is £5K and I’m saving c£150 per year it’s going to take years to make it pay if at all
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Not the same thing, but related and useful nonetheless are solar diverters - essentially a unit that switches on your immersion heater (or other device) when you would otherwise be exporting electricity to the grid. We had one fitted when we had our panels installed and this supplies all our hot water from April to October for free (we switch off the boiler for the summer). They cost about £300 IIRC so pay back time is very fast - of course it depends on whether you have a hot water cylinder or not. If you do have a generation tariff then you still benefit from the same payments as they assume you export 50% back to the grid. Solar iBoost is the model we have, reliable so far...
I looked at the batteries a few times but the numbers don't stack up for me yet - a substantial long term investment for sure.
Not the same thing, but related and useful nonetheless are solar diverters - essentially a unit that switches on your immersion heater (or other device) when you would otherwise be exporting electricity to the grid. We had one fitted when we had our panels installed and this supplies all our hot water from April to October for free (we switch off the boiler for the summer). They cost about £300 IIRC so pay back time is very fast - of course it depends on whether you have a hot water cylinder or not. If you do have a generation tariff then you still benefit from the same payments as they assume you export 50% back to the grid. Solar iBoost is the model we have, reliable so far...
I looked at the batteries a few times but the numbers don't stack up for me yet - a substantial long term investment for sure.
Originally Posted by Franky Four Fingers
Pretty much. Based on current engery prices and how much you generate/export.
I worked it out that I would pretty much break even after 10 years, but it was something I wanted to do, and could afford given I am getting about 55p/kw, just for generating.
Whoever does not know how to hit the nail on the head should be asked not to hit it at all.
Friedrich Nietzsche
I have one of those as well.
Whoever does not know how to hit the nail on the head should be asked not to hit it at all.
Friedrich Nietzsche
I was going to be completely off grid at the farm in Australia, so solar and batteries would have been a necessity. It would have taken 2 Powerwall battery installations to accommodate my needs, and be relatively comfortable - but using a gas stove, to reduce high drain things at night like a kettle etc. It’s possible with a bit of planning. I have a small number of friends who are not connected to the grid, but there is a lot more sunshine hours in Australia compared to the UK.
I will need to check if I can have solar on the new house; possibly not an option but we will see.
It's just a matter of time...
Not quite, in the summer months I’d expect somewhere in the region of 10-15kw in a day during the summer months , the 2400w rating is the maximum rating for an hour so you could potentially generate 2400w every hour for however many hours of sunlight. If you aren’t getting a feed in tariff batteries would make more sense I’m not sure of the prices for install etc but they could effectively wipe out your electric bill or cut it by 60-70% at a guess must be wor5 doing the maths.
As someone else said if you have a hot water tank definitely look at a diverter to immersion heater we’ve had one for years an have 6~ months a year of free hot water
A rhetorical question.... You say you cant use any export tariffs. Worth double checking the new SEG tariffs available that came online 1st Jan. The best pays just over 5p / kWh.
Prices have changed a bit since this table was put together..... https://www.solarpowerportal.co.uk/n...re_minimum_seg
You need a smart meter and a registered mpan which the supplier will get for you.
You don't need to have an export tariff with your import supplier.
ITK
R.
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