Hot tub solar
- Thread starter WJazz
- Start date
40A x 240V = ?watts
How many solar panels do you think you need?
Batteries?
How fat is your wallet?
I want to save $ long term... looking to keep hottub at a low heat and provide the rest buy fire. That’s another story...
I want to be able to maintain 80 degree heat to hot tub through the cold winters (can be -20 here). I was thinking 600w in panels and 2 battery’s. But if there is an ac input won’t that take over if the solar isn’t doing enough?
Thinking I would try it out and add if needed?
I want to be able to maintain 80 degree heat to hot tub through the cold winters (can be -20 here). I was thinking 600w in panels and 2 battery’s. But if there is an ac input won’t that take over if the solar isn’t doing enough?
Thinking I would try it out and add if needed?
schmism
Solar Addict
You'll want to figure out if this is a single heating element or are there 2.
If its a single 240v then when the tub is on with the pumps its rated to draw 9600w.
your going to want to run 48v. 4 - 3kw units in parallel or dual 6kw 240v units or a single 10kw 240v unit ~$2500
280ah cells from the group buy here on the boards =$1700 this would net you some were between an hr and several hrs run time on battery.
48v*280ah=13440wh/5hrs of sun = 2688w 3kw of solar panels ~$1500
Napkin math says budget is $5k-8K
If its a single 240v then when the tub is on with the pumps its rated to draw 9600w.
your going to want to run 48v. 4 - 3kw units in parallel or dual 6kw 240v units or a single 10kw 240v unit ~$2500
280ah cells from the group buy here on the boards =$1700 this would net you some were between an hr and several hrs run time on battery.
48v*280ah=13440wh/5hrs of sun = 2688w 3kw of solar panels ~$1500
Napkin math says budget is $5k-8K
mitchofcanada
Dirtbikes, Beer, Wifi.
swedish hot tub best bet...
MisterSandals
Participation Medalist
I am guessing you do not get more than 3 hours of sun in the winter.
How many "solar hours" of sun do I get per day throughout the entire day at a city near me?
I'll take some of the joy out of this and SWAG that this needs to run 10% of the time to keep the water at 80 when its -20 out. So that puts it at 2.4hours of runtime.
40A x 240v = 9600w
9600w x 2.4h = 23,040wh
23,040wh / 3hr solar = 7680w of solar panels
Assuming you need to store (24-3)/24 of this in batteries for when the sun isn't at peak:
Assuming 12.8v battery(s):
(7680w / 12.8v)/ (21/24) = 685ah of batteries (double that if lead acid which can only be discharged 50%)
Yep!
curiouscarbon
Science Penguin
- Joined
- Jun 29, 2020
- Messages
- 3,022
this video comes to mind. it’s a bit silly, but feels relevant to the topic.
good luck with your solar tub. i think it’s an awesome challenge idea
totally agree that 280ah cells seem appropriate here given the load requirement
good luck with your solar tub. i think it’s an awesome challenge idea
totally agree that 280ah cells seem appropriate here given the load requirement
Thanks everyone! More specifics...
I’m in western South Dakota. I would say between 3-6 hrs per day in winter.
And I need to figure out how much the tub is using next... we are paying 40$ per month right now with the hot tub at 98 degrees during the week and 104 on the weekend...
what if I just get a system and see how much heat I can get? Realistically if the solar keeps water above freezing that’s fine...
also is there a way for the solar to ‘help’ the power usage?? Can I switch the hottub power from solar to house ac?
I’m in western South Dakota. I would say between 3-6 hrs per day in winter.
And I need to figure out how much the tub is using next... we are paying 40$ per month right now with the hot tub at 98 degrees during the week and 104 on the weekend...
what if I just get a system and see how much heat I can get? Realistically if the solar keeps water above freezing that’s fine...
also is there a way for the solar to ‘help’ the power usage?? Can I switch the hottub power from solar to house ac?
If there isnt power in the batteries the the controller just shuts off power so they don’t drain too low right? I still want to estimate like everyone’s doing, but then I just want to buy the system and see...
I think $3000 would be my max investment...
so maybe some recommendations for the best $3000 system that could handle this kind of load???
I think $3000 would be my max investment...
so maybe some recommendations for the best $3000 system that could handle this kind of load???
EDIT. You get 3.2 to 4 hours sun in winter with panels angled for winter and facing South
Solar Irradiance Calculator
www.solarelectricityhandbook.com
Gonna cost you thousands for panels, racking, wires, inverter, scc, etc, and even minimal batteries to save less than $40 a month.
You do the math.
Heating water in South Dakota in winter with solar is going to be very expensive.
Last edited:
MisterSandals
Participation Medalist
Agreed.
It may be more cost effective to switch to a natural gas spa heater. These normally heat quite a bit
faster than electric so can be run on-demand more than hot all the time.
2009Bounder2020
New Member
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- Dec 28, 2020
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- 111
if you want a cheap option to just keep it from freezing you could use a farm sinking tank deicer. they are less than $100 and run on 120 volts mine is 1500 watts. After having a hot tub heater burn out once we keep one in our tub in the winters as a backup.
then use your campfire hydronic heater (im guessing this is what your saying you wanna do). and there is nothing better than a fire by a hotub to make a winter evening more enjoyable.
but dont try to heat the tub with solar and batterys your could build a addition to your home for less.
then use your campfire hydronic heater (im guessing this is what your saying you wanna do). and there is nothing better than a fire by a hotub to make a winter evening more enjoyable.
but dont try to heat the tub with solar and batterys your could build a addition to your home for less.
Good idea. Like what they use for cattle water tanks. So I use multiple systems to offset costs.
1. insulation around tub
2. Power the other from hot tub and a cattle deicer with solar.
3. Yes, hydronic heat from a stove
4. The tub will still be hooked to grid system for those cold winter nights...
what about water filled solar pannels? I love the idea but how are they used when it’s below zero? I guess they circulate 24/7???
1. insulation around tub
2. Power the other from hot tub and a cattle deicer with solar.
3. Yes, hydronic heat from a stove
4. The tub will still be hooked to grid system for those cold winter nights...
what about water filled solar pannels? I love the idea but how are they used when it’s below zero? I guess they circulate 24/7???
2009Bounder2020
New Member
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- Dec 28, 2020
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simple way would be one of the mpp all in one units that will recomments, or build your own from components.
get 3 full size panels and whatever flavor of 100AH @48 volt batterys to start.
technically you should figure out your "load" before getting the equipment, but with this use( the temp thats gonna vary,) its alsois the tub in the sun during daylight? how much insulation?, beef up the insulation etc. would go 48v no brainer.
get 3 full size panels and whatever flavor of 100AH @48 volt batterys to start.
technically you should figure out your "load" before getting the equipment, but with this use( the temp thats gonna vary,) its alsois the tub in the sun during daylight? how much insulation?, beef up the insulation etc. would go 48v no brainer.
So the 48v 3kw all in one. 700$
Solar panel x 4 $320
Batteries 2la $550
Cables $120
$1690 investment
am I on the right track?
And there’s room to expand to more batteries/panels should I see fit...
Then I just see how well it heats the water and expand if needed?
Solar panel x 4 $320
Batteries 2la $550
Cables $120
$1690 investment
am I on the right track?
And there’s room to expand to more batteries/panels should I see fit...
Then I just see how well it heats the water and expand if needed?
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,508
Why use batteries to store power for when the sun isn't shining?
Get an electric water heater. Heat it to a higher temperature and use a thermostat (and optionally timer) to run a pump circulating whenever tub drops below desired temperature.
Get an electric water heater. Heat it to a higher temperature and use a thermostat (and optionally timer) to run a pump circulating whenever tub drops below desired temperature.
Even a tub deicer on solar is going to cost a fortune in batteries and panels to power. And unless your hot tub is inside a building it isn’t going to keep pipes from freezing in SOUTH FRICKING DAKOTA! I lived in Newell for 3 miserable winters... nope, nuh-huh...
to keep a hot tub from freezing there, and the pipes inside it, you will need a building around the tub, and a large heat pump running keeping that space warm.
Resistive heating water is crazy demanding of energy...
1500W x 24 hours is 36KWh of batteries... at 48V that is 750AH for one day... and you will need 5 days minimum due to lack of sunshine IN WINTER in SFD... SO, 3750Ah of batteries...
using average Battleborn pricing (I know... you can build for less yourself... but not a lot less... figure a BEST case of 1/3 Battleborn pricing...)
50Ah 24V BB IS ABOUT $900 each... on sale, with coupon... so, carry the one... um... 38K in batteries...
Now... you need enough solar to recover the 36KWh daily use... divide by 3hours of average winter sunlight... that’s 12000 watts of panels for one day of recovery...
you would need to double that so you can cover the daily use, and recharge the bank some... 24,000 watts of panels... just to keep a 1500W heater going one day...
and a hot tub that isn’t in ground... is going to need way more than 1500W to keep the pipes from freezing.
it’s been a while since I lived there... maybe global warming has softened the winters there since I left in 83... but if I remember correctly, the frost line was 6’ there... so, the tub would need to be below that to keep from freezing...
“Beef up the insulation” is not realistic... build a building around the hot tub, and have THAT built with significant insulation... keep a minisplit running to keep the building above 32F... might be possible on solar...
to keep a hot tub from freezing there, and the pipes inside it, you will need a building around the tub, and a large heat pump running keeping that space warm.
Resistive heating water is crazy demanding of energy...
1500W x 24 hours is 36KWh of batteries... at 48V that is 750AH for one day... and you will need 5 days minimum due to lack of sunshine IN WINTER in SFD... SO, 3750Ah of batteries...
using average Battleborn pricing (I know... you can build for less yourself... but not a lot less... figure a BEST case of 1/3 Battleborn pricing...)
50Ah 24V BB IS ABOUT $900 each... on sale, with coupon... so, carry the one... um... 38K in batteries...
Now... you need enough solar to recover the 36KWh daily use... divide by 3hours of average winter sunlight... that’s 12000 watts of panels for one day of recovery...
you would need to double that so you can cover the daily use, and recharge the bank some... 24,000 watts of panels... just to keep a 1500W heater going one day...
and a hot tub that isn’t in ground... is going to need way more than 1500W to keep the pipes from freezing.
it’s been a while since I lived there... maybe global warming has softened the winters there since I left in 83... but if I remember correctly, the frost line was 6’ there... so, the tub would need to be below that to keep from freezing...
“Beef up the insulation” is not realistic... build a building around the hot tub, and have THAT built with significant insulation... keep a minisplit running to keep the building above 32F... might be possible on solar...
And, the problem with a minisplit in SFD is snow... I recall drifts 60’ deep when I was there... so... keeping the unit out of of the snow line is wise...
let’s see... maybe you live near hot springs? Can you access geothermal for heat? How is your house heated?
let’s see... maybe you live near hot springs? Can you access geothermal for heat? How is your house heated?
I like finding odd ways to do things... maybe we can find a way cheaply.
what town are you in? I sold fruit boxes for my school FFA class to most neighboring towns when I lived in Newell and I had to deliver them... I had just moved there and I outsold the entire class... I called every name in the phone book pitching school apples and oranges... everybody else in class just asked friends and relatives... teach was freaked out how many truckloads I sold that week...
what town are you in? I sold fruit boxes for my school FFA class to most neighboring towns when I lived in Newell and I had to deliver them... I had just moved there and I outsold the entire class... I called every name in the phone book pitching school apples and oranges... everybody else in class just asked friends and relatives... teach was freaked out how many truckloads I sold that week...
