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What is likely to happen, if anything, if I try and export to the grid and import from the grid simultaneously?

Andrew J

I have this scenario:  I want to export from a house battery to the grid during the period 23:30 to 01:00 at 3.6kW (until battery is empty.)  At the same time, I have my car plugged in charging at 7kW.  Would that have the net effect of pulling 3.4kW from the grid?  Is anything likely to fail?

As a basic summary, I can charge my house battery up at 7p from 23:30 to 05:30 and discharge it to the house during the rest of the day, thus I pay only 7p for electricity used.  I don't fully discharge the battery during this period so I can sell the remaining charge back to the grid at 15p before fully charging up again ready for the day.  However, I also need to charge my car up which I also do 23:30 to 05:30 - Note because of the tariff I am on I have NO control over when the charging actually occurs so I cannot configure it to avoid the time period where the house battery is discharging.  Re-configuring the battery to not discharge when I plug the car in is a laborious process which I want to avoid.  I only actually charge the car once or twice a week.

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  • I am kind of joining the party late and because I don't have an EV, the post and responses initially came across as a very unfamiliar George Jetson kind of world.  For instance I had not even heard of a house battery.  I am wondering one thing though... if someone didn't have an EV... is the setup scalable.... can someone have multiple house batteries which they charge up during the cheap time and sell back at a higher rate later in the day?

  • in reply to dang74

    Technically, yes, but inefficiencies nab you. I suspect that if it were a good deal more and more would do it, thereby balancing everything out and then it becomes more and more uneconomical, especially if buying a new battery just to do this.

    I've heard of a few using old EV batteries for this sort of thing; especially EV owners. That is, when the EV needs battery replacement to improve performance & efficiency they take the old battery and place in the home etc. Then it's a no-brainer as you've already paid for the battery.

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  • in reply to dang74

    Technically, yes, but inefficiencies nab you. I suspect that if it were a good deal more and more would do it, thereby balancing everything out and then it becomes more and more uneconomical, especially if buying a new battery just to do this.

    I've heard of a few using old EV batteries for this sort of thing; especially EV owners. That is, when the EV needs battery replacement to improve performance & efficiency they take the old battery and place in the home etc. Then it's a no-brainer as you've already paid for the battery.

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  • in reply to BigG

    I see what you mean by how if everyone started doing this...demand would go up during the overnight hours which would raise the rate.  I guess the other factor preventing this is that like anything promising savings on your utility bills, it takes a number of years to break even due to the upfront cost of the equipment.