What happens with excess power?

Wet1
Wet1 Registered Users Posts: 4
So I'm trying to decide how large of a system I want to install, but I need to understand what happens with surplus power. 

I have fairly low requirements today, yet know I will have to add an EV or two in the future at some point, not to mention I'd like to use this system to utilize my mini-split for additional heating during the winter (I usually stop using it from mid Nov-March) and also heat DHW with a HHWH.

On average I only use about 7.5-8kw per day right now, but it's been trending up and with the additions mentioned above, I'm sure there will be much more demand in the future,  I live in CT, I'm grid tied, but would like to get a hybrid inverter with a limiter to avoid exporting (I understand what this means, and I have no interest in having big brother in my affairs any more than necessary), and have backup power during outages.

With this said, I was thinking about doing a 6kw to 8kw system, likely adding batteries later.  So my question is, what happens with the excess power I generate through the system if it doesn't get exported to the grid and if there are no batteries (or if they are already full)?  Does the inverter just force the panels to go into VOC?  I'm assuming this is the case, and if so, is there any harm in doing this?  I'd rather buy the larger (AIO) inverter today (8kw?) and not have to add on in the next year or two as needs increase.  I'd likely install only 2kw to 4kw worth of panels initially, but even this will likely be way more than I need today.  I just want to make sure there's no issue with doing so before I start buying/installing stuff...  

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    excess power just is not used.  nothing is damaged. Solar PV may run just a few degrees hotter because you are not extracting power from them.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Wet1
    Wet1 Registered Users Posts: 4
    Thank you Mike, I appreciate the validation! I have a lot of large panels and while I could install them, I realistically know I can't utilize all that power so I wanted to make sure I don't do more harm than good by prematurely oversizing at least that portion.  I will likely go with an 8kw inverter and install a little over what I need as I go. My thoughts are having more than I need will help cover even cloudy days.

    Strangely, I'm having a harder time trying to figure out what to do with all the potential panel power I have!  One can only use so much DHW, air conditioning, dehumidifiers in the basement, etc.  Heating seems like a good use, but solar is limited in the winter and only available during the part of the day when it's needed least.  Battery storage is expensive.  Maybe use the house as a "battery" and overheat during the day, letting it cool at night?  And what to do with it during the long summer days?   Maybe I should look into mining crypto currencies, lol!   Or just locally sell some panels...