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I think most people would be happy to just charge the thing up via solar during the day and use it at night.

ryan-allen 12y ago
Even if it was powered from the grid, if these were installed everywhere you could have distributed charging mechanisms, which would lower the peak load on the grid, which would mean less peak power required across the board. There should be savings there as well!
ghshephard 12y ago
It's the opposite though - during the night, you want to use power from the utility, when it's plentiful, and cheap (particularly if you have a TOU contract). The objective would be charge the battery up at night from the grid, and then use that power during the day + your solar power, when power is expensive.
- nhaehnle 12y ago
  Once solar becomes widespread enough, the dynamic changes. In Germany, electricity spot prices can be lower around noon because of solar energy. A quick Google search brings up this example: http://cleantechnica.com/2012/03/23/german-solar-bringing-down-price-of-afternoon-electricity-big-time-more-charts-facts/ http://cleantechnica.com/2012/03/23/german-solar-bringing-do... (note that this already happened in 2012!)
  - jimmcslim 12y ago
    Spot prices could even go negative, depending on the rules of the market. That's certainly a feature of Australia's National Electricity Market (NEM) which covers the eastern states. The price can drop to a floor of around -$1000/MWh, so at these times the large generators are paying the network for the privilege of keeping their running - which they are generally forced to do, since such a period of negative prices doesn't tend to last long... certainly not long enough to justify shutting a coal-fired turbine down and then the expense of spinning it back up again.
- marssaxman 12y ago
  If you have solar panels, daytime power is as cheap as it gets. The cost of daytime power is negative for me, since my home solar array produces more power than I can use. Net metering is an accounting trick which lets you treat the grid as a big storage battery. My house "charges up" this battery during the day by running the meter backward; then I can "draw down" the battery at night, when my panels are inactive. If I had a literal storage battery at home, the economics would work exactly the same way: but instead of externalizing the cost of the battery onto the public utility, I'd be paying the cost myself by purchasing the battery.
  - ghshephard 12y ago
    Very few people have an excess of power from their solar grid - unless they aren't at home (which, come to think of it, is an excellent use case for a home battery). For most people, the home battery is going to be useful from day one by entering a TOU contract with their local utility, and then charging at night, and using the power during the day. Solar power, on top of that, will be a bonus. For the summer, California E-6 Residential rates are $.32/kWh during peak times, $0.13/kWh during off peak. If your house is using, say, 4 kW, for 5 hours during peak - then that 20 kWh will cost save you 20 * ($0.32-$0.13) = $3.80/day in power costs, approx $115/month. Do that for 4 months/year ,that's $460/year. With a 5 year life, that battery would need to be less than $2300 to come out even. http://cleantechnica.com/2014/09/05/teslas-gigafactory-may-hit-100-per-kilowatt-hour-holy-grail-ev-batteries-report-predicts/ http://cleantechnica.com/2014/09/05/teslas-gigafactory-may-h... suggests that $100/kWh is in the ballpark - so this might make sense right out the door.
- hyperbovine 12y ago
  My point is that most people would be perfectly happy just to say that they're no longer reliant on burning fossil fuels to power their homes. Life is just too short for me to care about arbing the residential electricity market.
Brakenshire 12y ago
That is effectively a form of arbitrage, I suppose. You're charging the battery when electricity is either cheap (middle of the night), or free (from solar on your roof) and then using it in place of expensive day time electricity. You could argue using battery electricity in stead of bringing in grid electricity is functionally equivalent to selling it to the grid, both in terms of pricing incentives, and the effect on the grid – in the same way that people are discussing being able to switch fridges on and off minute by minute as being equivalent to building grid generators which can be switched on and off on that timescale.

Even if it was powered from the grid, if these were installed everywhere you could have distributed charging mechanisms, which would lower the peak load on the grid, which would mean less peak power required across the board. There should be savings there as well!

ghshephard 12y ago

It's the opposite though - during the night, you want to use power from the utility, when it's plentiful, and cheap (particularly if you have a TOU contract). The objective would be charge the battery up at night from the grid, and then use that power during the day + your solar power, when power is expensive.

nhaehnle 12y ago
Once solar becomes widespread enough, the dynamic changes. In Germany, electricity spot prices can be lower around noon because of solar energy. A quick Google search brings up this example: http://cleantechnica.com/2012/03/23/german-solar-bringing-down-price-of-afternoon-electricity-big-time-more-charts-facts/ http://cleantechnica.com/2012/03/23/german-solar-bringing-do... (note that this already happened in 2012!)
- jimmcslim 12y ago
  Spot prices could even go negative, depending on the rules of the market. That's certainly a feature of Australia's National Electricity Market (NEM) which covers the eastern states. The price can drop to a floor of around -$1000/MWh, so at these times the large generators are paying the network for the privilege of keeping their running - which they are generally forced to do, since such a period of negative prices doesn't tend to last long... certainly not long enough to justify shutting a coal-fired turbine down and then the expense of spinning it back up again.
marssaxman 12y ago
If you have solar panels, daytime power is as cheap as it gets. The cost of daytime power is negative for me, since my home solar array produces more power than I can use. Net metering is an accounting trick which lets you treat the grid as a big storage battery. My house "charges up" this battery during the day by running the meter backward; then I can "draw down" the battery at night, when my panels are inactive. If I had a literal storage battery at home, the economics would work exactly the same way: but instead of externalizing the cost of the battery onto the public utility, I'd be paying the cost myself by purchasing the battery.
- ghshephard 12y ago
  Very few people have an excess of power from their solar grid - unless they aren't at home (which, come to think of it, is an excellent use case for a home battery). For most people, the home battery is going to be useful from day one by entering a TOU contract with their local utility, and then charging at night, and using the power during the day. Solar power, on top of that, will be a bonus. For the summer, California E-6 Residential rates are $.32/kWh during peak times, $0.13/kWh during off peak. If your house is using, say, 4 kW, for 5 hours during peak - then that 20 kWh will cost save you 20 * ($0.32-$0.13) = $3.80/day in power costs, approx $115/month. Do that for 4 months/year ,that's $460/year. With a 5 year life, that battery would need to be less than $2300 to come out even. http://cleantechnica.com/2014/09/05/teslas-gigafactory-may-hit-100-per-kilowatt-hour-holy-grail-ev-batteries-report-predicts/ http://cleantechnica.com/2014/09/05/teslas-gigafactory-may-h... suggests that $100/kWh is in the ballpark - so this might make sense right out the door.
hyperbovine 12y ago
My point is that most people would be perfectly happy just to say that they're no longer reliant on burning fossil fuels to power their homes. Life is just too short for me to care about arbing the residential electricity market.

Brakenshire 12y ago

That is effectively a form of arbitrage, I suppose. You're charging the battery when electricity is either cheap (middle of the night), or free (from solar on your roof) and then using it in place of expensive day time electricity. You could argue using battery electricity in stead of bringing in grid electricity is functionally equivalent to selling it to the grid, both in terms of pricing incentives, and the effect on the grid – in the same way that people are discussing being able to switch fridges on and off minute by minute as being equivalent to building grid generators which can be switched on and off on that timescale.