Battery storage on the grid

My friend Ian Woofenden has this to say about using batteries on the grid:

Tesla Battery Perspective

There’s been a lot of buzz recently about the Tesla battery. My attitude and ideas toward it are tempered by 30+ years of living off-grid with renewable energy technology and watching the industry progress. There’s plenty to say – my summary looks like this:

* It’s just a battery. Off-grid folks have been living with batteries for decades. They are not magic, and in fact they are often the biggest problem components in renewable energy systems. If you can avoid batteries, I advise you to do it!

* Batteries are actually a load on a system, since they are not 100% efficient and they have a standing loss. Adding more battery adds more load (and more cost). If you can grid tie without batteries, you’ll have the most efficient and environmentally friendly renewable energy system. If you need batteries (off-grid or utility back-up), I suggest you keep your battery relatively small, and invest in more generating capacity instead of more heavy metals that need care and replacement.

* It’s not a real product until it has a price tag, a warranty, and a track record.

* Early specs on the product make me scratch my head about whether the engineers even looked at the current renewable energy technology and how their product might interface with existing systems and gear.

* If the grid needs more storage, it is not your problem. Let the utilities solve that issue; they have a sweetheart deal with a profit-guaranteed monopoly – they can figure out any real storage problems. If you think you need storage personally, ask yourself the hard questions — how often and how long do you actually have utility outages, and do you really have critical loads?

* Perhaps the biggest drawback of the media focus on this prospective product is that people will get distracted from a true star of the renewable energy show — photovoltaics. Solar-electric modules are warranted for 25 years of energy production, and just sit on your roof or in your yard making electricity for you. They are ultra reliable, almost maintenance free, and will last longer than many of you reading this will live. My first modules went on the roof above me in 1984 and are still making clean electricity for my homestead.

* Perhaps the biggest benefit of the Tesla hoopla is that people will start thinking harder about renewable energy. Once they realize that this product is not magic, is expensive, and in itself really does very little for the average homeowner, they might start to ask smarter questions and make better energy decisions. Reputable and experienced renewable energy dealers and consultants are getting plenty of inquiries due to the Tesla hype; the wise ones are using the opportunity to help people understand the practical and cost-effective ways to achieve their energy goals. There is no silver bullet that can solve your energy problems quickly, easily, or cheaply.

Ian’s website is here.

In the United States (where Ian lives) they often have a Net Metering arrangement where the electricity they export to the grid is credited at the same value as what they use.  This reduces the incentive for storage.  But even when the exports are “lost”, as in “not credited to the householder”, there is not a big financial case for using a battery.  The latest new battery announced in the UK for example (article here) stores only a couple of kW hours.  Even if used to the full every day this would earn less than £100 over a whole year.  Batteries are expensive and they only last a few years.  Let’s focus on making renewable energy and investing in the equipment that makes the energy.

About hugh

I live off-grid in NW Scotland and have spent my life playing with wind turbines. I also love small hydros. Hands on renewable energy is my thing and I like to learn and to share my experiences.
This entry was posted in People, products/technical, wind systems tutorial. Bookmark the permalink.

17 Responses to Battery storage on the grid

  1. Blake Slade says:

    Some people are always trying to save some money on car batteries. But this is absolutely wrong. As a car mechanic, I always suggest for using Tesla battery. I think they will increase their popularity day by day.

  2. Alice says:

    As a car lover, I really appreciate Tesla battery. It can make a big change in the car industry now and in the future.
    Tesla company is leading at the electric car area and non-driver car.
    It saves our environment and energy.
    But they still have some mistakes that cause the accidents in the world.
    They are trying to do their best to give their best shot.

    Thank you so much for your share and have a nice day!

  3. Currey says:

    Looking forward to how the Tesla car change the battery industry since the cars would only be successful if the batteries are special.

  4. Young Hayes says:

    Great post! Thanks for the given information~

  5. Harry Silver says:

    I think Tesla battery is good, and I no way can avoid battery. Perhaps I can reduce using it.
    Anyway, your post is really informative. Thanks for this post~

  6. Oh, admin! Your advise had better be considered but how I can avoid battery. It is really difficult for me. I know that they are not 100% efficient but what I can use excepting it.

  7. patrick furey says:

    the same but 12vDC – 240vAC

    a fully qualified electrical engineer could easily adapt a Safe system with these products I’m sure.

  8. patrick furey says:

    if I could give any advice,it would be to stay well away from the tesla powerwall and similar products and learn about the components that go into lead,(sulphuric) acid batteries or al least stock a good supply of refillable batteries,(the old type).
    you can bet your bottom dollar that as soon as 12/24v lead acid batteries are phased out the price of these so called eco batteries and their maintenance will skyrocket.
    can a solid state relay do the same job as a charge controller…ie regulate the power to 230/240v as used to be the case on the old type electrical boxes….
    they c0st less than £20 and surely,2 of these in series could be as good if not better than a charge controller of the digital type.
    even better,can a potentiometer be constructed to regulate around 240v but be adjustable from around 120 – 415v (3 phase)?
    I wonder……

    • admin says:

      hi Patrick
      Off grid systems do use diversion loads to control battery charge rate, and I have done some pages about wiring up such controllers to manage the charging of off grid battery systems. Yes you can also use an SSR to switch AC diversion loads on and off via your inverter, and I have taken to doing this quite a bit. You do need more than just the SSR however – you need the logic behind it and sometimes this would be an auxiliary relay in an MPPT controller or inverter, sometimes I piggyback on the DC output of a tristar diversion controller. The SSRs you show on amazon are not big name brands and I prefer to use Crydom ones and make sure I use well under their rated current so they will be reliable. I even use phase-control SSRs to adjust the power diversion to large loads such as water heaters. But the hard part tends to be the control side of things and the easy part is the SSR.

  9. Nick says:

    i am a fan of Tesla battery. Thank for your informative article

  10. Mark says:


    “I honestly do not believe that battery prices will decrease, why should they at a business plan level ?.”

    Why not? Electric vehicle batteries have come down in price 40% since 2010. What cost barrier have the manufacturers hit that stops the price declining further?

    According to the Rocky Mountain Institute complete grid defection is economic in some markets. Their figures show that is clearly the case in Hawaii. The Australian energy minister Ian McFarlane thinks pv and batteries are going to be disruptive of the electricity market in Australia(

  11. Leslie says:

    I honestly do not believe that battery prices will decrease, why should they at a business plan level ?.

    For us here in Normandy, with 63kW of battery storage, we receive NO FIT’s or grants for our RE creation.
    However, at present under normal circumstances the standard Utility Grid will always be more efficient. Unless ……

    We are a standard large House, (to Passive House Standards) that requires normal energy use and 63kw, 48v is a sensible size as a buffer storage without excessive draining and re-charging cycles. And as we move towards a fully integrated AC Coupling, using pre-owned/second-hand GTI’s, (Grid tied Inverters for PV).

    However, we have used/second hand, carefully chosen, 12v 160ah, Gel types, that are just out of service, Corporate/Company UPS/Telecoms systems of 4 years, but have a 12 year life.

    So we are re-cycling batteries, and more importantly because of the reduced cost of our batteries we can beat the Grid/Utility Companies of about 0.25Euro per kWh.

    So for us, we use the Grid as a standby generator.

    Most folk who have PV on the roof would like to be power independent, but with the figures I have seen coming from the, ‘ back up boys’, the batteries are going to get severely hammered and will not survive the so called Unit Life.

    Unfortunately for us we seem to be in the crossfire. As we get ridiculed by the ‘Off Grid brigade’ because we should be using the Utility Grid, and dismissed by the ‘FIT brigade’ for not taking Government Grants.
    We would love to encourage folk to be more electrically independent, but at present the figures just do not add up, if you go down the Commercial Unit purchase route.

    Make it, and install it yourself, now you are talking. …………..

  12. Mark says:


    I’ve only skimmed the summary, ‘The Economics of Load Defection’ published by the Rocky Mountain Institute, but I think the graphic entitled Economically Optimal System Configuration (for business and residential)


    supports my suspicion that batteries are going to turn up in homes and businesses.

  13. Mark says:

    All very well but if people think they can save money by buying batteries they will. Not the state of affairs at present but it may be soon. PV and battery prices are declining and are likely to do so for a bit yet. A variety of price-points may be significant including the price of grid-tied electricity.

    If electric vehicles become a major part of the transport sector their owners may well agree to let utilities tap their batteries while parked, during periods of high demand when the price of grid electricity is expensive. Downward pressure on price looks inevitable.

    • admin says:

      Yeah of course people will buy stuff, but from what I have seen they get sold stuff that is not a good deal, such as rooftop wind turbines and vertical axis toys, and so when I see stuff being mis-sold then I like to tell it like it is. I am all for electric vehicles (I have one powered by wind) and if they can help the grid to cope with variable sources and demands that is great indeed. But buying batteries so as to fiddle the deal with export tariffs (exports are not usually metered under FiTs) is not a big step forward for mankind. Nor is it actually likely to be profitable once you do the sums.

Leave a Reply

Your email address will not be published. Required fields are marked *