for many it’s only the cost of the electricity
not to wax poetic.. it’s also about the autonomy for me, that’s very valuable
I did not mean to suggest that breaking even in 5 years is the only motivation to go solar, merely that achieving a 5-year break-even is a big challenge and places severe constraints on equipment choice.
And in particular I was questioning the claim that a 5-year break-even could be achieved with a Solark-based system (which I now understand is easily possible for a large enough system serving large-enough consumption).
i try to appraise the value of independence and somewhat factor that into the cost of the hardware.
paying for grid costs less, but costs more if autonomy is factored in so to speak.
all these systems are inspiring to me.
big thanks to
@GXMnow for explaining the context of their build.
i don’t know how anyone can stand to have a solar system that shuts off when the grid goes down!
I don’t know if you’ve already gotten your system in place yet or not, but I’ll add my experience in case it provides more insight.
I started with a 4kW Microinverter-based system under NEM in 2016. Overbuilt in anticipation of a hoped-for EV so electrical bills dropped from $700 annually to $0 and then back up to $120 when they changed the rules and decide to impose a minimum $10/month usage charge.
Between switching the oven from gas to electric, adding a kegerator and my son building a fancy new gaming PC he spends more hours than I want to admit gaming on, our consumption has now increased by ~25% consuming pretty much all the excess production I’d built to charge an EV.
I’m addition, our electrical rates have increased by ~25% since 2016 which on it’s face isn’t an issue since NEM means they credit at the same rate they charge, but then once you factor in the change in peak TOU window from noon to 6pm where it was in 2016 to the 4pm to 9pm peak window they are going to by 2023, and that translates to a ~17% reduction in annual generation credits coupled with an ~11% increase in consumption costs.
The net of all of this is that I went from paying $0 for electricity since 2016 (betting the $120/year in non-refundable charges) to having to pay $120 for electrical consumption at my last true-up this August.
Then you add in the new fire-prevention-motivated multi-day grid outages that result in good spoiling despite that 4kW of solar sitting idle, and the need to add a battery with capability for both backup during outages as well as time-shifting to cover increased consumption costs from 4-9pm was clear.
I ended up building a 14.3kWh LiFePO4 battery sufficiently big to power the full house for a full day, though my current 120V 3kW PSW is only large enough to power one leg of critical loads such as fridges during an outage (so no roast Turkey during a blackout for us
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To charge the battery, I added a new 1.1kW DC-coupled array on another face of my roof tied to a 60A MPPT charge controller (Epever AN).
During peak months of June to September, that array charges the battery with 6-8kWh of energy on Sunny days (more than enough to supply peak consumption from 4-9pm).
To offset that peak consumption, I added two 120V 1kW GTIL inverters, one per leg.
Those little inverters only cost me $275 each and they are powered from the LiFePO4 battery and can deliver up to 800W per leg to offset self-consumption. They use CT sensors on the L1 and L2 grid only wires to monitor grid consumption and generate offsetting power to maintain consumption if 5-10W per leg (as long as consumption is not greater than their 800W max output level).
I’m very happy with how they have performed so far (3 months in). They offset all of my peak consumption from 4-9pm over June-to-September peak months and consume all of the remaining day’s production by continuing to offset consumption into the night until the battery is depleted.
Efficiency of these little GTIL2 inverters is poor at 80%, but at a cost of $550 for 1.6kW output capacity, I can’t complain.
All-in, I’ve spent $500 on panels, $250 on SCC, $550 on inverters, and ~$500 on remaining BOM, or $1800 total for a system that should offset over $400 of consumption charges annually.
Another $300 for the PSW that only gets used once or twice a year during PSPS events and $1500 for the 14kW battery that is the heart of the system.
The battery is more three times the size I need right now but we’re still planning to get that EV, and once we do I’ll be able to add more panels to offset the increased consumption without making any other changes.
The $550 + $250 + $300 = $1100 I spent for GTILs + SCC + PSW may not last as long as I’d like and may eventually be more convenient being replaced with a hybrid inverter that would automatically switch to backup power when the grid goes down, but seeing the trend, I believe it’s likely we’ll see 3kW all-in-one hybrid inverters for under $800 within the next year or two.
Maxed out to a full 4kW DC-coupled array, I should be able to offset as much as 3750kWh of consumption with a system that cost me about $5000 in material cost.
That would translate to a best-case break-even of about 6 years or even 5 years if the solar tax credits remain in place when I eventually expand the system (ignoring installation costs since I did everything myself).
