GMP powerwall customers…feedback?

Submitted by slightlyrottensalmon t3_xy4eqz in vermont

I just signed up for a Tesla powerwall installation - current timeline is January. My original plan was to install a whole house generator, but powerwall seems like a better plan considering it potentially benefits more than myself (rate buffers, variability of electricity pricing given the New England grid’s reliance on fossil fuel generation, etc).

I don’t know anyone personally who has installed one, so I’d love to get opinions from those who have them and especially those if you who made the decision to install for the same reasons I’m heading that way. Also for those who have them, who was your installer?

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Real-Pierre-Delecto2 t1_irfkd5p wrote

Have one single unit got it years ago with a much better deal from GMP $15 a month lease and free install from Tesla themselves. Could not be more happy with the thing although at times they draw down to zero and while it's never caused any issues I pay for it for backup reasons not to save GMP money so if its really getting drained I take it offline. They do have a storm policy where they won't use it with a coming storm though.

How does it work? Awesome I almost can't tell if the grid goes out the switchover is sub 20ms or so almost invisible nothing electrical goes off or resets. It's rated at 5k per unit and I have pulled more 6ish for a few mins with no issues either. 2 units should be enough to power your whole house even with electric hot water although thats a hog anyways and you might want to shut that off in a long outage situation. My main complaint is it's not the easiest thing to hack but I am working on tricking it into thinking my generator is the grid so I can use it to charge the powerwall. It's also just about dead quiet liquid cooled etc. Also the app is handy just a few clicks and I can go off grid in seconds and that's real handy when a t storm is coming in as it physically disconnects the two hot lines from the pole outside. Anything else just ask.

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Thick_Piece t1_irfo919 wrote

I may be misinformed but I thought it was bad to draw those down to zero?

Does the batter put off heat?

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Loudergood t1_irfur5t wrote

Almost every lithium battery has built in circuitry to cut off before they get drawn to damaging levels.

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Real-Pierre-Delecto2 t1_irfqgay wrote

Not with the newer chemistry. They are rated for 4-8k cycles depending on the battery. They do get warm when charging but the unit is liquid cooled with a really nice radiator inside so no issues. Maybe if it was installed outside in the desert you might but not here in a VT basement or garage. Some even newer batts are rated at around 40k cycles thats about your lifetime!

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SomeConstructionGuy t1_iri6pit wrote

I think many manufactures are calling the low cutoff voltage 0% charge now. This lets them more easily communicate that the battery is at to 0% of capacity without the confusion of customers seeing a pack at 300v and wondering why it’s empty.

Edit: spelling

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Thick_Piece t1_irfoz6g wrote

As far as using your generator to charge it, I have a kill switch in my electrical box so I can directly connect my generator with a 220 plug.

Would it know the difference? I am curious as I wanted to get those batteries and figured I could just cycle back and forth. Use the battery until it is dead, start generator, charge batteries and have the house running on the generator.

I honestly have no clue how they work but they must know when the power is coming through the lines instead of a generator?

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Real-Pierre-Delecto2 t1_irfrr5d wrote

Sadly yes it does. And for disclaimer reasons don’t do this don’t try it ever unless you really understand what you are doing. It looks for a very stable frequency on the mains before it connects so you would have to have a real nice genny preferably an older very large 1600rpm unit that is more stable with lots of rotating weight. When the initial draw of about 4k comes to bear the genny will slowdown a bit until the motor catches up this causes the frequency of 60hz to drop and the Powerwall thinks that's the start of an outage and disconnects.

Also the way the unit is wired in you would have to add yet another disconnect because you would put the genny wires upstream of the Tesla box and without that you would be back feeding into the utility lines which is a big no no and can kill workers who might be in the area not expecting power to be on a line. It's not just the battery box there is also the "gateway" where the relays and brain are stored.

I want to do just as you suggest but I am not quite there yet.

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Thick_Piece t1_irftide wrote

I will take your disclaimer to heart as I have no knowledge on the matter. I was thinking of trying to figure out how to do the same with the standard deep cell marine batteries as I figure my electrician could figure out how to transfer some of the generator power over to the batteries or simply use a battery tender to do the same. Then Tesla came out with these batteries and I wondered if it was an option.

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Real-Pierre-Delecto2 t1_irfvkq5 wrote

Ya I hoped for that as well. The thing is very sensitive to power fluctuations which actually makes it work really good especially in my area. Where I live the mains have auto-breakers so if a tree or something touches the line they will trip but then re-engage a few seconds later to see if the fault has cleared. They do this up to about 5 times and it creates a huge surge in the house on-off on-off etc it's horrible for sensitive electronics. Use to have to run across the room and shut off the tube amps and other radio gear I have on. That never happens now as the Powerwall switches over so fast and wont switch back until it has about 5 mins of constant mains power.

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hudsoncider t1_irfeal0 wrote

What was the total cost? It’s a lease right or do you own them outright?

Edit - Nm I looked it up, 10 yr lease and $5500 total for 2 batteries.

Do you have to pay for installation on top of that cost and if so how much is it ?

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slightlyrottensalmon OP t1_irfgxil wrote

Single upfront payment of $5500 or $55/month. $2200 from GMP towards the installation. I don’t have a formal estimate for the remainder of installation costs. A bit strange that you have to sign up to get total cost estimate, that’s why I’m asking here. Hoping for some real world positive and negative experiences from those who already have them.

That single upfront payment is considerably less than what I was looking at for a generator (and dependence on natural gas to run it).

I’m not completely committed if feedback steers me elsewhere which is nice.

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hudsoncider t1_irfhar2 wrote

Yeah reading through it it does sound like a pretty good plan. I’d imaging the $2k should cover most of not all installation costs but definitely interested to hear if I’m completely off.

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Real-Pierre-Delecto2 t1_irfoohy wrote

IMO you should always stay away from propane and ng generators for fuel availability reasons. Yes I might seem paranoid but if the shit really hits the fan I want to be able to quickly fuel my generator. Gasoline and diesel and also veggie fuel will be avail for much longer. Remember also that nat gas is pumped with electricity so if the outage was catastrophic your generator would be useless. Prolly would never happen but I am kinda prepper minded and think of that stuff. On another note even if you get a powerwall I would still get a generator just a cheap one though couple hundy's down at Harbor Freight type of deal just to run your fridge or other essentials with an extension cord. Depending on where you are in VT we can and do lose power for days.

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patonbike t1_irfj2pw wrote

I’ve had them for a while. I got it long ago that I didn’t pay for install so not sure of that. I have no concerns except that of course their power output is limited to like 30 kWh. It’s enough for most outages.

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Distinguished_Parrot t1_irflz1t wrote

Not a customer personally, but maybe somebody from VEC will read this and offer something similar to GMP's program instead of their paltry level 2 charger offer for up to $300 credit.

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Loudergood t1_irfuj4i wrote

You're talking about completely different products here. But I agree, I'd love to to have a power wall deal like GMP customers get.

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Bernaroo t1_irfv1e8 wrote

The VEC flexible load program is better than GMP’s lease program in my opinion.

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couldbeyourex t1_irgpbat wrote

In my home we have 2 installed. They are amazing. One thing to keep in mind if your production ends up with net meter credits to your GMP account these will not be able to be applied to the $55 lease fee and you will always be charged monthly for the 10 years of your lease if you go the monthly fee route. Beyond that we were told we will have the option to keep them for 5 additional years to their 15 year life span max for no additional charge. But, we’ll see in 8.5 years if that is still the case. Our installer was Tesla, a small crew out of chittenden county and they were great. No install fee. This was in spring 2021. I say go for it

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slightlyrottensalmon OP t1_irgrn19 wrote

I don’t have solar, so these would be pulling from the grid. No net metering concerns.

Presume if I pay the lump sum, the units go with the house if I sell it? Vs if I make monthly and the house sells the buyer has to agree? Or is it like the water heater - just something buyers accept?

I’m really appreciative of the feedback!

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couldbeyourex t1_irh2clf wrote

There is a lease cancellation fee of i think around $500 if the new buyers did not want to assume the lease through GMP and they would remove them. If you bought them outright and included them in the sale of the house then include the value increase on the list price. But yes I would ask GMP directly regarding if you were to buy them outright if you could remove them if you sold the house.

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jsolt t1_iric4wa wrote

I did this in conjunction with the installation of solar and worked with SunCommon - GMP purchased one of my powerwalls in exchange for the ability to tap into it several times a month. Being the first year it looks like it will cover about 80% of my energy (heat, AC (heat pumps), electric, hot water) needs. Love it

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