Can Powerwall be configured to reduce demand charges?

Can Powerwall be configured to reduce demand charges?

Can powerwall be configured to lower demand charges? For example, when load exceeds 10kW can powerwall kick in to keep the utility load to 10kW?

tkaiser | November 10, 2017

Currently there is no way to setup triggers like that in the app.

However the energy for your loads should be supplied by the solar panels, whatever the panels cannot cover is supplied by the Powerwall, and whatever the Powerwall cannot covered is supplied by the utility. So that 10kW load could largely or entirely be supplied by a combination of Solar + Powerwall(s).

A single Powerwall supplies 5kW of continuous power. So you may need two powerwalls for a 10 kW load.

Earl and Nagin ... | November 11, 2017

My understanding is that what @tkaiser describes is exactly what will happen and it should keep the load under 10 kW for as long as you have charge in the battery. Remember that each PW holds 13 kWh so two full, new PWs will only be able to deliver 10 kW for 2.6 hours.

tes-s | November 12, 2017

Are there any plans to update the programming? I can see where the current programming is designed for places where there is no net metering.

But in places where there is net metering, demand charges, and/or TOU plans, there are much better algorithms to optimize ROI.

Related question - when grid goes down, does the standard installation have the PW power a subset of circuits, or is that something the installer would have to do external to the PW?

harrye | November 12, 2017

Software development is ongoing to provide richer and more flexible features. For example, ToU is scheduled for the end of this year (2017) or early next year.

By default, the PW-2 is installed either as a whole home or partial (critical circuits) backup. Essentially, the PW-2 connects to grid, solar and the home, solar powers the home, charges the battery and exports to the grid if the battery is full and there is excess. During lower light on solar, power is provided from battery and/or solar. Obviously at night, power is from battery and/or grid.

If the grid fails, the PW-2 acts as a UPS and is limited to 5 kW continuous power so this aspect should be considered as part of a whole home backup or just critical circuits. PW's can be combined in parallel to increase this limit.

There are more detailed descriptions of function elsewhere in the forums.


Harry E.

s.grot | November 20, 2017

Demand meters are typically on commercial users with 3 phase 480vac. Demand meters measure the highest average kw draw over any 15 minute period. We pay $20/kW ; and use 5000 kWhrs per month. So if the draw could be entirely leveled out it would be a 7kW continuous draw. We typically see 30 kW Demand charge; so it would save us $460/month. Our utility is shifting their revenue stream from kWhrs to Demand charge.

mark | February 21, 2018

I'm with you s.grot --- looking for ideas for my building to cut demand charge. I don't qualify for Tesla Solar on the building as I don't have enough usage but maybe a grid connected powerwall would take care of those peak demand charges. I am about in the same situation as you.

j.o.williams | August 15, 2018

I am also with s.grot. Don't know why rather then bringing the peak to the average of 7kw, how about bringing the peak to 0 kw? If the facility ran off of the battery and the batteries only drew power 13 out of every 15 minutes, then wouldn't the peak charges be $0? Saving $600 per month.

cwied | August 15, 2018

If the meter measures the kWh every 15 minutes and then multiplies by 4 to get the kW number, drawing for 13 of every 15 minutes does not drop the usage to 0.

george.whitridge | August 21, 2018

being able to do demand charge shaving w/ a powerwall would be amazing! I would strongly consider installing one at my inn if it were possible