Switching between Powerwall and power company

[Xminus6]

When my PowerWall was installed, it was made clear to me that the power utility would disconnect me if they found I was charging the PowerWall at cheap rate and selling the energy back to the grid at prime rate. So the issue may be with the power company, not the PowerWall. As a result, I believe UK installations cannot charge the PowerWall from the grid, only from PV. In any case, the gains are greatest when you are storing your own solar-generated energy rather than simply time-shifting your grid consumption. The SolarEdge inverter can be set up to disable the battery at certain times of day, so my setup doesn't use the battery during off-peak hours, when I am charging my car on cheap overnight electricity. (A typical car charge for me is 28 kWh so the PowerWall's 6.4 kWh wouldn't make much impression on that).

There is a semantic difference between charging at Off-Peak and selling back at Peak vs charging at Off-Peak and consuming at Peak. I can understand them not wanting you to buy their electricity for a cheap price to sell it back to them at an expensive price. But for those with solar and who are on a Time-Of-Use plan, I makes sense to charge during Off-Peak and let the house run off the battery during On-Peak to allow for all the solar generation to be sold back to the utility. You could say that functionally it's the same thing but I wonder if the regulations are different. For TOU plan users with solar, charging from solar and using at night makes no financial sense. It's actually a money loser to the tune of -($OnPeakRate-$OffPeakRate)*(PowerwallCapacity). So it would cost me somewhere around $0.33/kWh with my utility company.

 

[Ampster]

......the power utility would disconnect me if they found I was charging the PowerWall at cheap rate and selling the energy back to the grid at prime rate.....

Yes that is probably true in the US under a Net Energy Metering arrangement for the inverter that is listed in your NEM agreement. In my stationary storage system (not powerwall) that inverter does not connect to the grid so I am behind the meter and only subject to building codes. I charge at night at $0.11/kWhr and run my critical load panel during peak rate (between $0.27 to 0.37/kWhr. It frankly has a poor rate of return because I probably lose 25% round trip but it doubles as a power failure backup. I also rationalized it as a hobby and protection from rate changes. NOTE: Posted before seeing @Xminus6 post with similar comments.

 

[WannabeOwner]

the power utility would disconnect me if they found I was charging the PowerWall at cheap rate and selling the energy back to the grid at prime rate

Do you have a Net meter? My utility pays me for 50% of my PV generation (on the assumption that is what I export) as there is no actual metering of what I export. (Thought that was the norm in the UK, but it was a while ago that I had install, and did research!, and probably forgotten what-is-what in the meantime ...)

Incentive is for me to use 100% of generated PV, as Utility will pay me assuming I export 50% ... personally i think its a typical British Con; it works fine for me, I work from home, but most people will be out 9-5 and using zero power and thus exporting 100%