Avoiding a transformer upgrade

[lordofthereef]

Hello!

Been trying to do a bit of research as to what the best plan of action for our upcoming solar and battery backup installation might be. We previously sized a 15.2 kW system that is estimated to handle roughly 120% of our current needs. We do not have any EVs currently, but plan to in the coming years, hence the over sized system.

We have been informed that anything above 13kW will require a transformer upgrade, to the tune of $3200. Estimated savings on dropping down to the 13kW in solar panels and install costs is $5000, for a total of around $8000. The 13kW system seems like the way to go based on the numbers, but we were informed that Tesla (our installer) doesn't add panels to existing systems, so it seems like we need to size the system to our wants/needs out the gate. This is really what gives us pause, because we figured go with 13kW and then add panels down the line if our demand increases. Is this possible to do with other companies? Can we have another company add panels to an existing Tesla system if we wanted? Or are we genuinely "stuck" with whatever we have built day one?

Hopefully this is an appropriate place to ask. Found the forum based on others mentioning builds requiring transformer work from the utility, and if I am understanding correctly, it's par for the course for the consumer to have to foot that bill. I realize a bit of this is subjective in that it depends what our plans are, but hopefully I can get some insight from people more knowledgeable than I am on the subject.

 

[electrofelon]

The decision on if a transformer upgrade is necessary is of course up to the utility, and costs will vary widely depending on the details of their tariff. One thought: presumably it is the AC KW value that would matter for transformer sizing, so one option might be to just go with a higher DC/AC ratio thus giving you more production without a higher AC output.

 

[jaggedben]

Can we have another company add panels to an existing Tesla system if we wanted? Or are we genuinely "stuck" with whatever we have built day one?

Another company could almost certainly add a separate additional system. (As long as we're not talking about the Tesla Solar Roof being involved.) Few other companies have that blanket policy. However doing things in two stages will be less cost effective.

Hopefully this is an appropriate place to ask.

Not really, this forum is supposed to be for professionals. But as long as you're not doing the actual work as a DIY project it may be okay.

 

[lordofthereef]

Another company could almost certainly add a separate additional system. (As long as we're not talking about the Tesla Solar Roof being involved.) Few other companies have that blanket policy. However doing things in two stages will be less cost effective.


Not really, this forum is supposed to be for professionals. But as long as you're not doing the actual work as a DIY project it may be okay.

They are panels, not the tiles. I was surprised to hear Tesla's policy on this, which is why I was seeking additional knowledge on the subject. Glad to hear it's not a technical limitation.

I did read the rules and it seemed to be vague on the specifics, however my initial post needed moderator approval before being viewable by anyone else, so I figure it's ok too.

 

[lordofthereef]

The decision on if a transformer upgrade is necessary is of course up to the utility, and costs will vary widely depending on the details of their tariff. One thought: presumably it is the AC KW value that would matter for transformer sizing, so one option might be to just go with a higher DC/AC ratio thus giving you more production without a higher AC output.

This is something I should bring up with the installer?

 

[electrofelon]

This is something I should bring up with the installer?

Yes. If they are competent it will make sense to them.

 

[curt swartz]

If you want any flexibility or customization of your system Tesla should be your last choice followed closely by SunPower. They offer decent pricing but zero customer communication or support. They will designing a system based on what they think you need and that is what you get. The installers are robots programed to do what they are told and noting else.

I have talked to many people that have had project take over a year from start of installation until system is functioning. Also trying to get them back out is near impossible.

Just had a customer that needed some panels removed and reset for some roof work part of an addition. Also needed the inverter moved about 10'. They put many calls into Tesla over several months and never got a response. They ended up finding another company to do the work. They tried to get me to do it but since this was a lease (power purchase agreement) system I didn't want to touch it.

If you want a custom system with options and good support you are better off going with a smaller local company.