> I wish I could run a water heater, heating or fridge off this system to use the excess 270Wh of the daily energy production.
Or better yet, be able to sell the excess power. In the future power grid this will be possible.
Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
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Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#42Cool! The one thing I notice the author gets wrong is (out of modesty perhaps) claiming the system isn't very financially successful. But it actually is! > 200W system payback period: $300 / $48 = 6.5 years until payback > Either way you cut it, this is not a money saving machine. Energy prices are just too low. That represents like a 16% rate of return with little risk, which any investor would take in a second. How…
Unfortunately it isn't a 16% return because he can't sell that system for what he paid. If you buy a stock at $300 and sell it for $348, that's a 16% return. But for him, he probably would have trouble selling all of that for $100 (the battery will be worthless in about 2 years given how far it is being discharged and very few people buy these things on craigslist for anywhere near what they cost). If he can sell it…
Being able to sell the system is irrelevant as long as the system will last indefinitely (or say, 30 years, which approximates the same value anyway). Everything but the battery is solid state and should last indefinitely -- or certainly more than 8 years. I already excluded the battery as a consumable to calculate the 13% rate of return. But one thing you are right about is the other parts will fail eventually, dragging the return down as well.
Solid state parts can last decades though. The best way to calculate the rate of return would be to actually get accurate numbers for lifespans for all the parts and amortize them. It's probably greater than 4.5% and lower than 13%. Regardless, at near zero risk, even 5% is a great return these days, so it's totally worth doing.
Since you like the stock analogy -- a share bought at $100, that earns $10 a year, and that for whatever reason we confidently expect to keep earning $10 every year for decades, returns a 10% rate of return. The fact that the stock now sells for $50 makes no difference, as long as we believe we are right and the market is wrong about the likely future earnings.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#43I find the title kind of click baity, "$200 solar self sufficiency for my bedroom" would be more accurate
Hey. You're completely right :) My original title was was "Solar Self-Sufficiency for Renters", but my mates in marketing told me to clickbait it the f up. Would you have clicked on the former, though?
Your friend gave you good advice.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#44Earlier quoted context omitted.
Unfortunately it isn't a 16% return because he can't sell that system for what he paid. If you buy a stock at $300 and sell it for $348, that's a 16% return. But for him, he probably would have trouble selling all of that for $100 (the battery will be worthless in about 2 years given how far it is being discharged and very few people buy these things on craigslist for anywhere near what they cost). If he can sell it…
Being able to sell the system is irrelevant as long as the system will last indefinitely (or say, 30 years, which approximates the same value anyway). Everything but the battery is solid state and should last indefinitely -- or certainly more than 8 years. I already excluded the battery as a consumable to calculate the 13% rate of return. But one thing you are right about is the other parts will fail eventually, drag…
Honestly I think even my number is a little optimistic because I doubt his battery lasts 2 years. Most lead acid batteries are only good for 100-200 100% cycles. I also doubt that the PWM controller or the inverter last 30 years. I've seen failure rates as high as 50% for cheap PWM controllers like that after 10 years. The inverter is likely similar. Sure you can buy stuff that will last 30 years but that will be much more expensive. 8 years seems like an appropriate amortization schedule which puts my $100 at 6.5 years as a little generous.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#45Will the landlord notice? Maybe not. Will the wife notice all the wires all over the place? You bet!
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#46Far more cost-effective would have been to skip the battery and just put a cheap chinese pure-sine-wave grid-tie inverter to bridge between the wall outlet and the panel. It's simple- it has a 110V line cord and plugs into the outlet, sending current the opposite way of normal. Do a search on your favorite e-commerce site for "grid tie inverter" and you'll see what I mean. These cheap inverters have most of the same…
The two big reasons not to do this are his own words:
"cheap" and "chinese."
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#47Far more cost-effective would have been to skip the battery and just put a cheap chinese pure-sine-wave grid-tie inverter to bridge between the wall outlet and the panel. It's simple- it has a 110V line cord and plugs into the outlet, sending current the opposite way of normal. Do a search on your favorite e-commerce site for "grid tie inverter" and you'll see what I mean. These cheap inverters have most of the same…
Wow that's really great input. I'm going to check this out and write a follow-up! This would allow me to credit the power directly to my fridge bill, as opposed to just using it for lighting and devices!
Do not do this. You could kill a utility worker, and it's against the law for safety reasons.
Edit: Net metering/grid tie guidelines require inverters that will shutdown upon loss of utility power. Also, a disconnect switch must be on the exterior of the building/facility, clearly identified, and on record with the utility.
Bonus points if you Google "lock out tag out".
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#48Quite a side note: If you're renting in SF, your landlord needs to provide you with heating (http://sfrb.org/topic-no-257-minimum-heat-requirements)
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#49> Unless you live on an RV or a boat it doesn’t make financial sense yet If you're curious about what a system for an RV does look like, I work remotely full time in an RV and built my own system: https://therecklesschoice.com/2016/04/29/diy-rv-solar/ 6.5 times the solar, 15 times the storage, 20 times the inverter (but mine is overkill for us honestly).
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Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#50> I wish I could run a water heater, heating or fridge off this system to use the excess 270Wh of the daily energy production. Or better yet, be able to sell the excess power. In the future power grid this will be possible.
It's possible today, almost everywhere in the USA. In fact, the power company will usually buy it from you at the same rate that they are charging. My house is turning the meter backwards as we speak.
To do this, you need extra components to protect your house, the power grid, and the electricians who work on it.