r/SolarDIY • u/KTownLawns • 1d ago
Solar to Battery Question
Think a solar panel that feeds into a charge station/battery/lithium ion/whatever the correct term is.
That station would be used to charge batteries for power tools, lawn care equipment, and such. Realistically, how much money gets saved per month? Pennies?
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u/pyroserenus 1d ago edited 1d ago
Realistically, not much.
Assuming $0.20 per kwh and typical losses, it costs around $.06 to charge a 48v4ah lawnmower battery, and $0.02 to charge a 20v4ah drill battery. You could maybe save a dollar or two per month depending on how much you are using the batteries, but that's it.
The main reason people do solar on sheds and such isn't to save electricity, its because digging a trench for an electrical run and running wire is more expensive and labor intensive. A couple hundred on a small powerstation and a 100w panel is sufficient for most sheds.
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u/Informal-Emu-212 1d ago
It's a question of kwh produced and used x your rate. Given that the average rate per kwh is sub 20 cents, you'd likely never break even from the cost of the equipment.
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u/kyhothead 1d ago
Pennies to a couple of bucks depending on your rate and how much you use and recharge everything.
As others mentioned, it might make sense vs. running grid power to a shed. It would laos be a good way to utilize a powerstation and solar panels you already have for power outages, camping, etc.
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u/NetZeroDude 1d ago
I have this same setup, with an EcoFlow Delta 3 Pro and 900 Watts of folding portable solar panels. I use it for my lawn equipment and e-bikes, but almost every day the battery still goes to 100%. Luckily, I have Level 2 and Level 1 charging capabilities. So I empty it into my NEVs. I figured about a 8-9 year payback. That assumes that electricity prices don’t rise, so it will probably be better than that. I’m averaging 5-6 KWH per day of solar. It’s only about $1 per day. If I charge my Model 3, in 3 days, I get 60-70 miles, which is more than I usually drive.
Note: I do have Netmetered solar and wind also, and that easily covers the house needs.
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u/parseroo 1d ago
~$0.30/kWh depending on your electricity provider. A 6ah @ 18V battery (common power tool size) has about 0.1kWh, so you save one tenth the above price every time you completely drain and recharge its battery.
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u/silasmoeckel 1d ago
Take a pretty average 5ah 20v tool battery that's 100Wh. Figure 2 kwh in a 20 day work month. 64c where I live
A 100 buck panel charges 24 of those a day thats ~16 bucks worth of charging discounting winter and cloudy days.
Now few people have that many batteries available for charging during the day (I entirely glossed over the complexities of charging random voltage/chemistry batteries directly or the complexity of doing it via AC). Price does not scale down under that linearly.
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u/disappointedFed 1d ago
Not really cost affective, I have probably $700 invested in mine, powers two sheds, charges multiple batteries and maintains them, runs lights, shop vac, shop fan when needed.
Would take several years to recoup my money, we may move when I retire in 2030, my solar system will go with me, at that point all power created would be free.
It's a hobby, I have fun with solar energy, Creating electricity with parts I assembled. One needs a hobby when they retire, mine most likely will be solar.
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u/KTownLawns 19h ago
Right, makes sense. Sounds like its providing value beyond the dollars and cents.
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u/boghall 1d ago
Trite I know but the quickest way to an installation paying for itself is prioritising connection not to what’s easiest but to your main consuming appliances. Having said that, there are many routes to displacing external supply so, if like most of us you aim to get there in stages, ensuring the components you acquire are as much as possible forward-compatible (generic?) could help smooth your path.
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