Does The Powerwall Have A Feature To Limit Grid Peak Draw?

[matt_net_zero]

I have a situation where our [non-profit organization] campus has tiered + metered electricity pricing. So long as we don't exceed NN kW at any point in time, our bill is fairly reasonable. If we were to exceed NN kW for even one minute in a month, we'd get bumped up to a higher pricing tier and our monthly bill would more than double from increased tier pricing alone.

If we had a Powerwall plugged in between our power meter and our loads, could we tell the Powerwall, "if grid consumption is at (NN minus 2) kW, then start discharging to keep the grid load below that tier?

 

[Musterion]

What you describe is typically called “peak shaving” to reduce energy demand charges. The commercial version of the Powerwall, the Tesla Powerpack, seems to have this capability/algorithm as one of its main features. Powerpack - Commercial & Utility Energy Storage Solutions | Tesla
However the Powerwall software does not yet seem to have this particular usage case built in. It might be possible to do it with the Powerwall using scripting and communicating with the Powerwall directly. If you do a search on “OhmConnect” and “OhmHours” here, you will see people trying to do something similar, but that is for a specific time period and not over all time of use.

 

[matt_net_zero]

Thanks! That’s exactly what I was looking for.

If I understand properly, with a Powerwall or two, we could charge the pack(s) when our consumption is low (20 hours per day) and then adjust the reserve percentage (with a script) so that the packs are discharging during the hours when we’re running the Really Big Motor?

 

[cwied]

Unfortunately the only "peak shaving" algorithm the Powerwalls have is to try to limit grid draw to 0. This means you can't target a non-zero level of usage. This means that it's hard to do exactly what you want. You could definitely adjust the reserve percentage to offset predictable high loads if you know when they're going to happen, but you'll use a little extra stored energy because the Powerwalls will take your usage to 0 instead of the acceptable threshold.

The scripting is not that hard. The idea is just to use the same endpoints that the installer setup wizard uses to adjust the backup reserve.

 

[NuShrike]

I have a situation where our [non-profit organization] campus has tiered + metered electricity pricing. So long as we don't exceed NN kW at any point in time, our bill is fairly reasonable. If we were to exceed NN kW for even one minute in a month, we'd get bumped up to a higher pricing tier and our monthly bill would more than double from increased tier pricing alone.

If we had a Powerwall plugged in between our power meter and our loads, could we tell the Powerwall, "if grid consumption is at (NN minus 2) kW, then start discharging to keep the grid load below that tier?

How many PWs does your NPO plan to have? PWs can't cover more than a day of electricity usage, depending on your usual daily load. If you're trying to do tier-limiting, you're going to need a lot of PWs.

It may be more economical to audit and budget your electrical usage with smart-plugs, and some gas/oil generators.

How are you going to charge the PWs -- the power has to come from somewhere. Grid-charging would obviously take it out of your tier-budget.

PWs can only time-shift electrical capacity. Does your utility allow you to shift to a different plan that isn't tier-based, but more time-based?

 

[Sailnavy]

Looks like the only time of use net metering plan for Dominion in VA is a demand time of use, so shaving the peaks would be the optimal approach to using the PW. The trick would be figuring out the set point. Hopefully Tesla adds the feature to Power Walls soon. Also an oddity here is a split peak hours. Some in the am, then off peak, then on peak in the pm.