Differing quotes

Hello,

I have two quotes that are both from reputable companies but they are very different and I can’t make out which one is closer to being correct.

There will be two arrays in the final analysis - one on a southern facing roof and one on a western facing roof that is also slightly north. The money was pretty equal so I am not worried about that. Can you tell me what you think about each proposal?

The annual usage is 13,003 kWh.

Proposal #1: 45 Q-Cell 315’s with 45 Enphase micro inverters. 100% grid tied with no back up. 28 panels on the southern roof and 17 on the western roof. (maybe 26 and 19 depending on fit)

Proposal #2: 34 Mission 305’s with a StoreEdge SE76 and P320-5 Optimizers AND an LG RESU10H battery (this system is actually a little cheaper despite having the battery).

My concern is that I really want to cover my usage with a little buffer and I can’t understand how these two quotes could be 11 panels apart - with the larger panels being the most numerous. Any thoughts or comments would be appreciated!! Thank you!

Hi @jjclara

They are indeed very different.

You are using approx 35kWh per day on average. Quote one is about 15kW and quote 2 is 10kW of solar. Assuming you’re in a reasonably sunny part of North America, that will equate to about 60kWh a day for quote 1, and 40kWh a day for quote 2. Both above your needs, quote 1 significantly so.

In most parts of the US I believe you are able to get a “net feed in tariff”, which means you receive the same amount of money for the solar you export, as for the solar you import. In which case I don’t really see the benefit of getting a battery. Do you know if you are able to get a net feed in tariff, or what the deal is in your state?

I would be inclined to get a 10kW system without a battery. In fact, if you can fit 28 panels on your south roof, I think that would suffice. 28 x QCells 315W with Enphase inverters would be my choice.

Hope that helps.

Marty

Hi Marty,

Thanks you!! I forgot to mention that we are in NH, so we do recoup money for excess energy produced.

The battery is being considered because we don’t have a generator- it is primarily for back up because we are so far north and would be lost if a significant power outage were to occur.

Do either of those things change your opinion?

Thanks you!!

Hi Julie

I guess that’s a personal decision whether you want backup or not. How often do you lose power up there? What do you have in place at the moment if you lose power? Wood fire? Gas? Do you really need the electricity backup?

As for sizing the system, I don’t think it makes that big a difference. I would probably still go for 28 panels on a south roof without storage, because it’s simple. But again, it really depends on how you feel about the need for battery backup.

Hope that helps.
Marty

Hi Marty,
Thanks for the reply! I am slow to get it but still appreciate it. We don’t lose electricity very often, truth be told, but plenty of people up here have generators… so it isn’t an uncommon concern. In the dead of winter a lot of damage could be done if the electric went out. We have a pellet stove (requires electric), a furnace (requires electric) and a fireplace (doesn’t).
I’m on the fence. Is there a way to install the system and add a battery later? I keep hearing that isn’t possible but I find it hard to believe.
Thanks again!
Julie

Hi Julie

You can most definitely retrofit a battery, my understanding this is now quite simple to do with the Powerwall 2, and other modern batteries. @Svarky, do we have an article that discusses this? I think I have seen it somewhere.

Hi Julie,

I am surprised both systems are the same price even though the first option has around 4kW larger solar array (panels are relatively cheap these days). The LG RESU-H 10kWh battery is quite expensive and SolarEdge is also not cheap so this seems like a very good deal. Do you mind providing a rough cost that you were quoted for each system?
I personally would be inclined to go with the SolarEdge system and have the security of back-up power considering the crazy weather which seems to be happening these days.

Hope this helps,
Jason

Hi Jason,
Thank you for your reply.
The first system came in at $33,900 for 45 Q-Cell 315’s using Enphase micro inverters
The second came in at $35,100 for 35 Mission 310’s plus an LG RESU10 using SolarEdge inverters with P370 optimizers.
I am leaning towards the system with the battery too. It just seems like the most value for the money and having back up would be peace of mind.
I’ll be interested in your reply.
Thanks!
Jjclara

Hi the prices quoted are reasonable for the US (but this would be considered expensive in Australia).
The cost of supply and installation in the US is a little over $2000 per kW so based this estimate (depending on your roof type and state reguations) the first option would be a little over-priced. Therefore the second option with the LG battery seems like a much better deal.

My only concern is that I’m not familiar with the ‘Mission’ panels, if you think the company is reputable then I would go with this option.

Jason