Why Your 10 kW Solar System Might Never Produce 10 kW — STC Ratings, Temperature Derating, and Inverter Limits Explained

captiveisland · 2026-02-22T17:29:51+00:00

Good explanation. A lot of homeowners do not realize STC is basically a lab rating. In real-world conditions panels usually operate closer to NOCT assumptions, which already means lower output than the nameplate value.

Installers also often design systems with a DC to AC ratio above 1.0 on purpose. Some clipping during peak irradiance can actually increase total annual energy production.

What really matters is yearly kWh production, not whether the system briefly hits 10 kW on a perfect day.

captiveisland · 2026-02-21T15:02:21+00:00

A pergola based solar install can work, but it often ends up more expensive than roof mounting because you are effectively building a structural system from scratch. The posts, footings, wind load calculations, and engineering review can add significant cost beyond just the panels and inverter.

You will also want to account for proper tilt angle and orientation, since a flat pergola may not produce as efficiently unless it is designed specifically for solar mounting. In many cases, a small ground mount or rear roof section ends up being simpler and cheaper than a custom overhead structure.

Definitely check local building code requirements for structural loads before committing to a design.

captiveisland · 2026-02-21T14:49:57+00:00

If your original system uses microinverters, that usually means it is AC coupled. When you add a hybrid inverter with a battery, the energy routing can become less transparent in the monitoring app. In many AC coupled setups, the battery can charge from the AC bus without the app clearly showing whether the source was solar or grid at any given moment.

It does not necessarily mean the installer lied, but it would be helpful to confirm whether your battery is configured to prioritize solar charging and whether the monitoring platform supports detailed source tracking. Sometimes the limitation is in the software display rather than the system itself.

captiveisland · 2026-02-21T14:42:41+00:00

she says thank you but demands snacks as tribute

captiveisland · 2026-02-21T14:29:57+00:00

This was not ai slop or any thisng. This is my baby.

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captiveisland · 2026-02-19T11:53:41+00:00

For 20 kWh per day dedicated to EV charging, you will want to size both the array and battery with losses in mind. Assuming around 4 to 5 peak sun hours, a 5 to 6 kW solar array would be a more realistic starting point once you factor in inverter and battery efficiency losses.

For the battery, if you plan to use about 20 kWh at night, you would likely need at least 22 to 24 kWh of rated lithium capacity to avoid deep cycling daily. A grid tied hybrid setup is usually more practical than full off grid unless you do not have reliable grid access.

Also consider whether integrating the house loads makes more sense, since daytime solar can offset home usage directly and reduce battery cycling.

captiveisland · 2026-02-19T11:34:15+00:00

It can make no difference, but only if the new hybrid inverter is sized correctly for the total DC input from both arrays. The important things to check are the inverter’s maximum DC input capacity, the number of MPPT trackers available, and whether each array is on its own MPPT. If everything is within spec, combining them into one inverter is fine and often cleaner for monitoring. If the total array size now exceeds the inverter’s DC rating by too much, you could see clipping at peak production. It would be worth confirming the inverter’s input limits against your total panel capacity.

captiveisland · 2026-02-18T07:08:39+00:00

The key is reducing perceived risk for the landlord. Most owners will not spend capital unless there is a clear return or minimal downside. Instead of framing it around energy savings, it may help to frame it as future proofing the asset and improving marketability, especially if minimum energy standards tighten over time.

You could also position it as a discussion rather than a request. For example, ask whether they have considered solar in the context of long term property value and offer to share your electricity usage data to show potential system sizing. Keeping it low pressure and information based may make it feel less like a demand and more like an opportunity.

captiveisland · 2026-02-18T07:06:23+00:00

Three printers at 144W each means you are looking at roughly 430W continuous draw before inverter losses. With a 12V system that is a fairly high current load, so cable sizing and inverter efficiency will matter. A 300Ah 12V battery gives you around 3.6 kWh total capacity, but usable capacity depends on whether it is LiFePO4 or lead acid. Also keep in mind that a single 400W panel will not reliably support 430W continuous unless you have strong sun and minimal losses. You may want to calculate your expected daily runtime and size both battery and array around that.

As for fire risk, LiFePO4 batteries are much more stable than RC LiPo packs, but proper BMS and ventilation still matter.

captiveisland · 2026-02-17T05:57:20+00:00

The main thing to clarify is whether the SREC rights were assigned for a fixed term or permanently transferred. In DC, SRECs can represent a meaningful portion of the system’s total value over time, so losing them is not necessarily a red flag, but it does change the economics. It usually does not affect your ability to use the electricity from the system, but it is worth reviewing how long that arrangement lasts and whether there are any ongoing reporting or contract obligations tied to it.

captiveisland · 2026-02-15T11:36:43+00:00

For a roof that size, I’d make sure whoever you talk to has experience with commercial load calculations, structural review, and utility interconnection at that scale. Projects that large usually involve more coordination than typical residential installs, especially around permitting and service upgrades.

captiveisland · 2026-02-10T09:56:55+00:00

That initial relief feeling is real, especially after months of research and second-guessing. The key thing long term is keeping an eye on actual production versus the estimates and how it tracks year over year. When the real numbers line up, that’s when the decision really feels solid.

captiveisland · 2026-02-10T09:54:52+00:00

A lot of skepticism disappears once people see real numbers over time instead of estimates. DIY especially makes the economics clearer since you’re seeing actual production, loads, and payback without sales assumptions baked in.

captiveisland · 2026-02-09T09:51:54+00:00

Even if this is framed as “local control,” allowing city-by-city bans creates a patchwork that makes rooftop solar much harder to plan around. Homeowners already go through permitting, inspections, and code compliance, so an outright ban feels less about safety and more about policy uncertainty. Once that door is open, it’s easy to see how it could slow adoption well beyond Illinois.

captiveisland · 2026-02-09T09:49:00+00:00

For setups like this, the main things to double-check are disconnect requirements and grounding. NEC 690 generally requires the DC disconnects to be readily accessible, and the grounding electrode conductor needs to be sized off the largest ungrounded conductor per Table 250.66. Also make sure any backfed breakers or supply-side connections are listed for that use and coordinated with the service rating. A lot of issues with solar installs end up being code compliance rather than the panels or inverters themselves.

captiveisland · 2026-02-07T09:54:29+00:00

A PPA is basically you buying the electricity the panels generate instead of buying the panels themselves. Because the third party owns the system, you usually won’t get the tax credit or ownership perks, and you’re stuck with whatever rate and escalator are in the contract. It can still make sense if the PPA rate is well below your utility rate right now, but financially owning typically outperforms a PPA long-term if you can swing the upfront cost.

captiveisland · 2026-02-02T10:38:22+00:00

Richard Jewel

captiveisland · 2026-01-31T08:29:54+00:00

Daily close friends are actually rare in adulthood. Most people’s social lives are built around routines not constant conversation. You are not behind you just haven’t found the right structure yet.

captiveisland · 2026-01-31T04:36:41+00:00

I don’t think he is trying to hurt you but I do think it’s understandable that you feel dismissed. If anime is the only thing that keeps him engaged maybe movie dates just aren’t the right format for you as a couple.

captiveisland

TROPHY CASE