Solar Projection v Estimates

We got a solar system in 2022 to try and fix some of our power costs and hedge against the future. We were fairly confident it would work well, but weren’t 100% sure. So far, it has reduced our power bill quite a bit, though it’s a bit hard to tell right now if this is actually saving much money.

However, the performance is above what was estimated. I’ve built a Power BI Report that tracks the actual production v the estimates. So fat, almost every month has beaten estimates and our power production is well above what we expected.

Given the fact that power prices have increased in CO and I expect more increases to come, this is nice.

I can’t embed the report here, but this is an image of the report:

Power BI report of production v estimates

I need to add some more costing here, but our current bill is often around $22/month, of which $13.50 is a connection charge. Usually we are paying around $8-12 of demand charges for peak usage from 4-8pm. Hard to get the family to slow down here, and there isn’t much solar during this time.

This is, however, much better than last Nov/Dec, when we had $220 bills. Even with the loan payment, I think we’re paying less than in the past.

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9 Responses to Solar Projection v Estimates

  1. Robert Sterbal says:

    This will be a frequently shared post.

    Thanks for sharing your experience.

    —Robert Sterbal 412-977-3526 mosaics:


  2. Dave Wentzel says:

    That’s pretty cool. You might consider sharing the economic arrangement…you mentioned “loan payment”. There are a few of these outfits that essentially give you the system for free and most states will actually pay you to backfill power to the grid. The marketing is that these outfits get to keep that revenue in lieu of an installation loan. I have some neighbors with complete horror stories about this. Essentially these companies attach a lien to your property for the installation. Seems reasonable…until you go to sell and suddenly you have a lien holder that can make your life completely miserable…to the point where they had to buyout the lien at a significant markup, just to sell their home. I’m quickly seeing what the real business model is here. Regardless, it’s clear this is the future.


    • way0utwest says:

      We own the system. It’s on a loan through a bank, just like a car. Is there a lien, sure. Just like if I took a loan for home improvement. That isn’t a nightmare in most people’s minds, but it certainly can be if you haven’t accounted for that.

      Sound financial advice: Don’t take loans on things you plan to sell within the term of the loan.

      In terms of what this means, we used to pay $200+/mo for power. The estimate in 2020 was around $180/mo across the year, but certainly some higher months. The system was about $170/mo, and we choose terms that worked better for us. We could have a lower payment, but it would impact other stuff.

      Instead we now have around a US$20/mo-$30 for power from the company. $14 of that is always there. The rest is a demand change for power consumption from 4p-8p. I try to remind people not to do power intensive things during that time as they take your peak usage in that time for the month and then charge a rate. Lots of people are struggling with this change. However, for us, it’s a $5-15 add on.

      For us, we pay USD$0.14/kWh. That’s going up. I’ll calculate out the cost from solar, but over time, that’s consistent, while the utility tends to avg 4.5%/yr rises over time.

      So far, we are seeing overall less cost to us across the year for power. Our loan+monthly < previous monthly.


  3. luther atkinson says:

    Curious if you added any battery backup to your system or not. But either the estimates were on the low side, or you’ve managed to optimize placement and angle of your panels for maximum performance. Good on you.


    • way0utwest says:

      Luther, no battery for us. We bought a whole house propane generator early on that is hooked up to the house for limited power and well purchases. We didn’t want to change that as it’s worked well for over a decade.

      Estimates were good, I think, but the weather in CO has been dry this year. One of the dryest, which meant sunniest, we’ve had. A mixed bag as I’d sacrifice some solar for more water, but it’s not my choice.

      Our placement is about perfect. Our house faces almost due south with no obstructions for hundreds of feed. So the panels get sun about as long as they can without having mechanical movement devices attached.


  4. Daniel says:

    Good for you. I know this article was about Power BI, but ultimately, we all want to save time, money, resources, and headaches. So, to snoop a bit, what brand/manufacture/solar company did you use? Just like database engines, not all solar panels are made equal.


    • way0utwest says:

      Daniel, I’ll write more on this with some details, and did a little here:

      We ended up with a local CO company that a friend had used twice. Good referrals. We had spec’d some LG 370W panels for the house, but during the design they were replaced, so we ended up with LG375QIC 375W panels with a 21.7% efficiency. LG is moving out of the market, but they are honoring warranties, so I’m not too worried. When I looked around, they were quite highly rated.

      Not sure of other hardware. So far, performance is pretty good.


  5. Dave in England says:

    Steve, If you add some batteries to the system then these could be charged up during the day during low power use, and then used during dark when the family is using power. Is this feasible?


  6. way0utwest says:

    Dave, we could, but the batteries change the economics and ROI. Plus, if we exceed the draw during the 4-8p, we’d still get charged something extra. The demand charge isn’t usage, but peak usage, which is weird.

    adding a battery would have been on the order of $5kish, maybe 4, maybe 6-7, but wit 5K, I’d need to try and calculate what that means for power. Assuming we never got a demand charge, which has usually been about $10/mo, or say $15. That’s $180/yr. For $5k, that’s 27 years to pay back. Plus, not sure if batteries would sustain us during extended outages. We’ve had 8hr ones in the past, so I don’t know that we could disconnect from the utility and save another $15.


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