Posted by: @editor

Batteries for home energy storage. Are they worth it? This is a question I've contemplated for two years.

So I'm opening the floor to everyone. Are batteries worth it in the short- to long-term? 

Mars, I thought about the pro's and con's of batteries and in the end I took out the initial financial consideration (although it is indeed a consideration !) and thought If I am installing solar and during peak solar I lose production due to not being able to export as much or nowhere to use it then its wasting production of power. by adding batteries I am really maximising the solar panels to gain the absolute efficiency out of them. I think people really should look at solar/Battery as a combined cost and not individually. 

You could technically just buy batteries without any solar, go on a great overnight tariff of 5.5p to charge them and then use the batteries during the highest tariff time in evening / morning. When people look to install solar they get a figure of the potential production that they may produce for the year and if you dont use batteries then potentially you may only benefit from a very small amount of that potential production as you didn't need or use it during the highest peaks. 

I think about 10 years is about right for the lifetime of the batteries but that doesn't mean they will just stop working it just means you will have less efficient batteries which in ten years you can renew or augment your battery farm. 

Not everything you purchase for your house will need to have a return on investment, some things are just nice to have, new TV or new carpets and curtains, Solar is nice and its green and batteries are useful to have as part of that mix. The cost of Electric/Gas/Oil in all houses is a necessary cost but how many people say what will my return be if I replace or buy a new Gas boiler ? they just get it as its an option, Solar is an option as well as batteries and they will be the standard in the coming years. 

Hi Mars/Bob,

From a solely financial aspect I would say quite probably no, even if you were to go for a cheaper option than that offered by Tesla. Though I urge everyone to buy one or even two Tesla systems plus a Tesla car, since I have shares in Tesla.

Joking apart, batteries do not produce any free energy, in fact the whole system will use some energy.

Batteries come into their own if you are totally off-grid, and combined with a sufficiently large Solar PV Array, can store enough electricity to cover 3 or 4 cloudy days.

The most cost effective way to utilise excess power from your Solar PV system, is a power diverter to provide free hot water and possibly more.

The unit I have can divert excess energy to up to 3 different loads (up to 3kW each). I have set my system so that when the Solar PV is producing more energy than our home is using, it initially diverts the excess to a 2kW electric heater located in the hallway. This is controlled by a programmable thermostat, which switches the heater off when the temperature reaches 22C or the time reaches 10 am. At this point any excess energy is now diverted to the second load, which is the immersion heater in the hot water tank. At 3 pm it switches back to the hallway heater, to give the home heating a boost before the sun goes down. I have also been contemplating electric storage radiators, heated by excess energy from the Solar PV, so that the gas boiler would be used less during the night in Spring and Autumn.

The next most cost effective way to use the excess energy is an ASHP (or preferably GSHP). This of course gives 3 times or more the heat energy than direct electric heating systems. Since your ASHP, if set up correctly, should not run its compressor continually, but will switch it on and off at a frequency dependent upon the loading, then it would be possible to also have not only water heating, but storage radiators to help out the ASHP during the night.

Another way that would probably be cheaper than a fixed battery system, is to have an electric car and V2G charging system. Though this would require careful planning of car use and battery charging to get best results.

There are a number of ways that energy can be stored, that are more cost effective, if not more efficient than batteries.

A footnote:

I was talking with my good friend who works for National Grid yesterday, and he was telling me that some companies have plans to create large battery storage of up to 500MW capacity. This would allow them to charge National Grid an arm and leg for supply, when the wind suddenly stops blowing or a cloud appears.

National Grid are also installing further undersea links to Iceland, Norway and Belgium, and from Scotland to England. This is so that National Grid, can hopefully get power from somewhere, when the wind stops blowing and the Sun stops shining. I hope this does not worry anyone too much.

@derek-m I think lots of countries are going to start to have interlinks of power supply with each other to make more power available when needed. The supply of power doesn't care where it is, only where it can get power from to meet demand. I can see lots of Batteries in the future to help provide a buffer of instant power when required, but that will be only during those times we cant meet demand from the renewables. Solar, Wind and Hydro are live right now and their current capacity will obviously increase. I think for Scotland we have the unique position where tidal and wave technology will begin to come into the supply when they begin to get more efficiency out of the tech. 

I like your use of the power without the battery but I still believe it has its uses as not everyone has the same setup and as you mention there are other ways but they too cost money such as heat stores for water etc. Ultimately virtually all new houses will have some kind of solar and I suspect battery going forward with the grid also using the EV to Grid power if required. 

Hi Bob,

I agree with you that batteries certain have their place in the future power grid. If I did not have a wife (don't tell her I said so) and therefore was rich, I would have all the latest gadgets on my ocean-going yacht.

Interlinks are fine to aid system stability, but what if some politician decided they could be used for political leverage?

I think the question that Mars posed was aimed at non-rich people like me, where our meager pittance would be better utilised on items that offer a better return on investment.

I watched some videos recently highlighting the research being carried out to produce almost 40% efficient Solar PV Panels and new battery materials that would produce lighter batteries, which could more readily be fast charged, provide much higher energy density and more charge/discharge cycles thereby extending their useful life.

Modern society is addicted to electrical energy, and they get very upset if someone takes it away.

I also watched a video the other day about plans to possibly convert the natural gas system in Germany to eventually be used for Hydrogen supply. Hydrogen being a green fuel if produced using a renewable power source.

My friend and I were discussing this very subject yesterday, and he was telling me that Centrica (National Grids subsidiary) was in trials to possibly introduce 10% Hydrogen into the mains gas supply.

I wish i was rich 🙂 but alas I’m just looking at costs that i can cover now and how to reduce the ongoing costs going forward. The German Hydrogen discussion is interesting (I lived there for over ten years) and I just dont see how the existing Gas system will be easily changed over to take hydrogen as there are a number of factors that need to be realised before that can happen which is in my opinion is a logistical nightmare full of issues., firstly people with gas boilers will either need to upgrade their existing boiler to take hydrogen or buy a new hydrogen boiler (some boilers just want accept an upgrade) thats FOR EVERYONE with a gas boiler. Then there has to be the switch over  from gas to hydrogen, do you say that on monday we will switch of the gas and Tuesday you will only have hydrogen ? How do you ensure the gas is empty and does the boilers that are upgraded or only hydrogen work if theres still gas ? Are we saying that there will be outages of prolonged periods of time for the change over ? Will there be a requirement that any hydrogen boilers installed now must be dual fuel (gas and hydrogen ) to ensure a smooth switch over ? But then you have to think how long would that actually take to achieve to upgrade / replace every single gas boiler in the land ? Its a major major task and there is a cost and for a lot of people it will be “why am i paying for this when i have a perfectly workable gas boiler). Then theres will Hydrogen be cheaper, same or higher in cost ? To the end user ? I’m think the same or higher will be the answer ! We live in interesting times.

Hi Bob,

I was playing Devil's Advocate again,

From what I can remember from the video, it obviously would not be overnight. If my memory serves me well, I think that they were saying it would be possible to mix up to 40% Hydrogen in with the present natural gas. Hydrogen is also being consider as a fuel for automobiles.

Unlike electricity, gas can be stored in bulk, so could be produced using renewable energy during the Summer months, for use in the Winter.

There are discussions taking place in various quarters about improving energy availability using all the different energy sources. The main discussion of the video was the possibility of utilising the existing gas infrastructure for Hydrogen rather than gas.

I agree with all the points you raised about the probable difficulties in achieving such a changeover.

I have fitted the Tesla batteries as you know and it will take time to totally evaluate but its a complicated calculations. With the prospect of fitting a ASHP this year my reasoning for the Batteries was to ensure I could capture all my Solar PV during the day to power the heat pump at night without drawing too much for the grid and that they could be recharged during the night in winter to take advantage of cheap rate green wind generated power. I my be a bit naive but it makes me feel good that my house at least could be carbon neutral from now on.

I took advantage of the zero % loan from The energy Savings Trust for both my Solar and my Batteries so the capital outlay was somewhat less. I also believe that this could be a major selling point for the property with energy bills at or close to zero, which in turn adds to the asset value as a whole.  

Take a look at Greenrock batteries in Austria. Completely green and recyclable, take them to your local recycle center when they're finished.

Their prices and output compare very favourably with the Powerwall last time I checked it was under £4000 for 5kWH.

I just wish they had a UK sales base.

They also have an amazing Home Energy Management system, which I'd love to have. Plug and play and self learning if you want that.

Unfortunately I'm going to have to go down the Raspberry Pi route with Home Assistant as I can't get hold of the Greenrock HEMS in the UK.

Hi Duncan,

Don't get me wrong, I am not anti-battery, I was answering Mars question from a purely financial aspect.

I don't think that it would be possible to recoup an £8000 investment in a Tesla Powerwall during its expected life. It would be necessary to make savings in the order of £800 per year. A DIY battery system may be more viable for those who can build one. For me, that is the route that I would pursue.

I may be wrong, but for me personally, a battery system would be a 'nice to have', rather than an essential.

At the moment I can utilise most of the output from my solar panels, even without an ASHP. I also take the view that when I do export power to the grid, it is possibly replacing a small amount of fossil fuel generation.

Solar panels and a battery system from the point of view of 'free' energy don't work too well in Winter. They work great in Summer, when you don't actually need that much energy unless you have Air Conditioning.

I have been following the Octopus Agile electricity tariffs, and have noticed that present prices are much higher than they were in 2019. Today's lowest price is 9.56p and the highest is 30.87p.

@derek-m I wasn't aware of the mix of hydrogen of us to 40% into the existing Gas so thats a fundamental mind change for me as I didn't realise it could be mixed. that then allows for the greening of the Gas supply chain and a change over period for people to go with a complete Hydrogen setup. 

Hi Bob,

Here is the link to the article that I mentioned. It makes interesting reading.

https://www.siemens-energy.com/global/en/news/magazine/2020/repurposing-natural-gas-infrastructure-for-hydrogen.html