On-grid domestic battery storage

Martyn1981 wrote: »

That said, I can see how a joint venture between the DNO's and pro-sumers (producer/consumers) like us could have financial benefits for everyone, so keep my fingers crossed for more (and better) offerings.

But ...... I really want a battery to play with!

Well, I've got a 40 kWh battery on the drive and it's quite capable of delivering all our domestic overnight needs. It can be charged either from solar only or E7, and is capable of discharging back into the house. All we need is a cost effective means of achieving it. Vehicle to grid is all very well but surely by using our excess storage from the car to only run our domestic needs then demand on the grid at peak times would also be reduced!:(

orrery wrote: »

Well, you might have, but isn't the whole idea of a domestic battery system to store solar energy generated during the day when you are out driving your EV and then using it to charge your EV overnight?

With this being the Green and Ethical section then charging with "cheap" E7 energy when 70% of it is made up of CCGT & Nuclear makes it difficult to reconcile!

Because of the above I'd never been convinced that EV's were paticularly green. It was only when it dawned upon me that we could make one so by charging totally from a Solar system installed on our property that we made the decision to go down that route.

Being fortunate in that we can charge our EV (or a storage battery if we had one) on 100% green solar energy during daytime hours then charging by alternate means, be it E7 or otherwise comes a very poor second. I appreciate that if you need the EV for work and away from home all day then what I'm advocating may not be plausible.

We all have differing lifestyles and goals. I merely made the point that for us our EV could fill more than it's original purpose and that V2G may not suit everyone.:)

Coastalwatch wrote: »

It was only when it dawned upon me that we could make one so by charging totally from a Solar system installed on our property that we made the decision to go down that route.

I'm glad that you've achieved such a thing - most people would find that impossible.


In the depths of winter a typical 4kWp system would generate less than 3kWh per day, with much of that going on the house background usage - so no real surplus for charging a car. Even in full summer, a 'typical' mixed cloudy/clear day would make it difficult to get 100% solar into the car (without spending even more money on a clever charger) and even that assumes that the EV is sat in the drive waiting to be charged during the day when most people would be heading out to drive their cars.


For most people with PV and an electric car, the "I charge my car from solar" is simply an aspiration which can't be supported by the data. For me E7 is far more sensible, using the PV to offset the background usage on peak rate, and subscribing to a renewable-only tariff.

NigeWick wrote: »

You're ignoring the smugness quotient. I know my PW2 doesn't make sense financially but I like to see how much of my solar it stops going to the grid. And, I can brag about it to anybody who will listen.

I am quite sure that solar + batteries will be cost effective in a few years and I like to think that as an early adopter, I am doing my bit to help the development of these technologies.

I agree. I may be wrong but I imagine most of us on this forum are blokes and we like our tech and by not having a battery, some fancy graphs and other data to play with you are missing out on some of the fun. Come on, use a bit of man maths and you can justify to yourself that you need a battery just like I have done.

Last year I used man maths to justify ordering a new Golf GTE (PHEV) as I was being offered a great deal but having waited 8 months for delivery I scrubbed that and bought a 2016 Golf tdi and splashed the rest of what I would be spending on my new solar panels and battery - again applying man maths.

We all make decisions and like to be able to justify our rationale to our peers and critics. It is hard for the minority of us who have committed to batteries to justify why we have become early adopters to the battery doubters.

I decided to get a battery at the same time as panels because I thought it would save a few bob on VAT and maybe installation, and because I wanted one. I also thought that Gridshare might work.

I don t actually know exactly how much my battery cost as it was part of a system. If someone can tell me how much a 7.8 kw system (26 x 300w mono panels) on two roofs with 2 inverters and IBoost should cost then I can work out the true cost of the battery.

I re-read the Moixa blurb and if you sign up to Gridshare you get unlimited warranty and the batteries I am told are replaced when they fall to 70% (of what I am not too sure). If Gridshare takes off and Moixa are making good profit selling surplus energy to the grid then it is in their interests to replace the batteries with more efficient ones. So hopefully that removes the argument regarding degradation.

My man maths projects a return/saving of £200 pa from the battery for the first 3 years with hopefully more to come from the profit share. If Moixa stay in business and the warranty is honoured then I should be ok.

I might have got it wrong but at least I have a new toy to play with.