diy solar

diy solar

Supplemental electric heating; 6kw inverter, 5kw of battery, 2kw of panels

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Redacted

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I am looking for the most efficient electric heat I can leverage my system for.

Right now, this is running critical load, ie fridge,freezers,pump etc.

I would like to have an electric heater kick on in the morning (before the sun comes up) to warm the general areas of my house.

We already have propane and an electric forced air to keep the house at a constant temp in the winter. This would just be to take the edge of when it's extra cold.

I think one of the standard ceramic space heaters would be fine, peak 1500w. But I am wondering if there is anything newer or more efficient that anyone has used.

I am in Canada, and we get to about -40C/F max a few times a year and lots of snow.

Thanks
 
Electric heat is the exact same efficiency, 100% regardless of medium. Ceramic, radiant, oil filled, eventually all electricity used by the device turns into heat.

I'd buy a cheap oil filled radiator and run that on the 800W setting. As a matter of fact I bought 5 of them and I am planning on dumping all my excess solar into them throughout the day, my system is a fair bit larger than yours.
 
GregTR said:
Electric heat is the exact same efficiency, 100% regardless of medium. Ceramic, radiant, oil filled, eventually all electricity used by the device turns into heat.

I'd buy a cheap oil filled radiator and run that on the 800W setting. As a matter of fact I bought 5 of them and I am planning on dumping all my excess solar into them throughout the day, my system is a fair bit larger than yours.
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Interesting I had not thought of it that way. I tend to overcomplicate everything lol

I just picked one of those up and am experimenting with it now.

How big is your system ?
 
I have 19.4 kW of panels, 33.6 kWh of batteries with a Sol-Ark 15K in the middle.

My system is sized for summer A/C usage but since I have gas furnace for heat I have a LOT of free solar in the winter that I have nothing to do with. Since my REP only gives me $0.03/kWh but I can save $0.05/kWh worth of natural gas by using the oil heaters I am planning on dumping the excess electricity as heat into the house instead of putting it on the grid.

I am thinking about putting in a couple mini-split heat pumps but the cost of running 240V across the house from the breaker and the cost of the mini-split system have really bad ROI when compared to the oil heaters. I estimated the ROI on the heaters to be 120 days but on a mini-split it would be years...

I got free night (9p-7a) electricity locked in for 2 years so I'm also going to run the space heaters all night with free power for the next two years which makes the mini-split heat pump even less of an ideal proposition.

When it's all said and done I'm estimating $0 electricity cost and about $600 worth of natural gas saving this winter with this setup.
 
That is quite a bit larger!
I am hoping to double or triple my panels and double my battery asap. Unfortunately Time of day charges are not available for me right now. When I break 600kwh it goes up in price. So I am trying to leverage as much solar as I can, while maintaining battery for backup as the grid is unreliable here.

I am hoping to be able to supplement heating 24x7 I just have a whole lot of math do to as far as battery goes. I have been trying to get it set up using the inverter to manage the BMS but that is not going well. I still have a lot of work to do.
 
a 1500w heater won't heat much more than an 8x10 room. that's a lot of juice for the amount of heat output.

you'd be better off investing in more insulation.
 
GregTR said:
I have 19.4 kW of panels, 33.6 kWh of batteries with a Sol-Ark 15K in the middle.

My system is sized for summer A/C usage but since I have gas furnace for heat I have a LOT of free solar in the winter that I have nothing to do with. Since my REP only gives me $0.03/kWh but I can save $0.05/kWh worth of natural gas by using the oil heaters I am planning on dumping the excess electricity as heat into the house instead of putting it on the grid.

I am thinking about putting in a couple mini-split heat pumps but the cost of running 240V across the house from the breaker and the cost of the mini-split system have really bad ROI when compared to the oil heaters. I estimated the ROI on the heaters to be 120 days but on a mini-split it would be years...

I got free night (9p-7a) electricity locked in for 2 years so I'm also going to run the space heaters all night with free power for the next two years which makes the mini-split heat pump even less of an ideal proposition.

When it's all said and done I'm estimating $0 electricity cost and about $600 worth of natural gas saving this winter with this setup.
Click to expand...

Free electricity for 10 hours everyday?

Man, don’t even need solar, just storage.

Which power company offers that? Did you have to sleep with the CEO?
 
x98myers7 said:
a 1500w heater won't heat much more than an 8x10 room. that's a lot of juice for the amount of heat output.

you'd be better off investing in more insulation.
Click to expand...

I agree with the first assertion but disagree with the second one.

Facts:
A 1500W oil heater can be had for $90.
I pay $1.55/CCF for natural gas at the moment (I can change so the math will change accordingly)
1 CCF of natural gas has about 103,700 BTU of energy
103,700 BTU is the equivalent of about 30.39 kWh of energy
My furnace has an 80% AFUE rating so I only get 80% of energy into actual house heat.

Therefore, my actual cost per kWh of heat energy that makes it to my house from gas: $0.064/kWh
My electricity buyback agreement gives me $0.03/kWh for energy I put on the grid.
Therefore my net gain of using the electricity myself to heat the house over putting the electricity on the grid is: 0.034/kWh
At that price I would need to generate about 2,650 kWh of energy with an oil heater to offset its $90 cost. If I generate about 20 kWh of excess energy every day in the winter my payback period is 132 days.

So buying a space heater makes absolute sense for me, even just to use up surplus solar.

Now, since I get 10 hours of free energy every day, I can use these space heaters even more and the benefit for every hour I use them at night. At 1,500W I can use 15kWh every night which is a fuel saving of $0.064x15=$0.96 each night. With that, and the additional excess solar use my payback is 55 days on the heater.

Now given that I get the free nights I actually bought 5 of these, one for each bedroom, one for my office and one for the upstairs open space. This way I can just not heat the upstairs all night and significantly lower the downstairs temperature at night, possibly saving even more on heating.

As soon as November rolls around I'll be able to give you actuals on the saving, but a space heater, no matter how little it contributes, it undoubtedly produces significant savings and the ROI is better than anything else in the solar realm.
 
Danke said:
Free electricity for 10 hours everyday?

Man, don’t even need solar, just storage.

Which power company offers that? Did you have to sleep with the CEO?
Click to expand...

Just Energy in Texas. 100% Green Nights Free Plan - 24 months. $0.29/kWh 7am-9pm, $0 9pm-7am.

You're correct, you would not need solar to take advantage of this plan, but without solar you don't get the federal credit and on my system the federal credit paid for my batteries.
 
GregTR said:
Just Energy in Texas. 100% Green Nights Free Plan - 24 months. $0.29/kWh 7am-9pm, $0 9pm-7am.

You're correct, you would not need solar to take advantage of this plan, but without solar you don't get the federal credit and on my system the federal credit paid for my batteries.
Click to expand...

I think someone posted here that under the recently passed bill, batteries alone also qualify for the 30%. Did you buy in 2021 or prior?

I’m kinda doubting power companies will be offering that deal after two years.
 
GregTR said:
I agree with the first assertion but disagree with the second one.

Facts:
A 1500W oil heater can be had for $90.
I pay $1.55/CCF for natural gas at the moment (I can change so the math will change accordingly)
1 CCF of natural gas has about 103,700 BTU of energy
103,700 BTU is the equivalent of about 30.39 kWh of energy
My furnace has an 80% AFUE rating so I only get 80% of energy into actual house heat.

Therefore, my actual cost per kWh of heat energy that makes it to my house from gas: $0.064/kWh
My electricity buyback agreement gives me $0.03/kWh for energy I put on the grid.
Therefore my net gain of using the electricity myself to heat the house over putting the electricity on the grid is: 0.034/kWh
At that price I would need to generate about 2,650 kWh of energy with an oil heater to offset its $90 cost. If I generate about 20 kWh of excess energy every day in the winter my payback period is 132 days.

So buying a space heater makes absolute sense for me, even just to use up surplus solar.

Now, since I get 10 hours of free energy every day, I can use these space heaters even more and the benefit for every hour I use them at night. At 1,500W I can use 15kWh every night which is a fuel saving of $0.064x15=$0.96 each night. With that, and the additional excess solar use my payback is 55 days on the heater.

Now given that I get the free nights I actually bought 5 of these, one for each bedroom, one for my office and one for the upstairs open space. This way I can just not heat the upstairs all night and significantly lower the downstairs temperature at night, possibly saving even more on heating.

As soon as November rolls around I'll be able to give you actuals on the saving, but a space heater, no matter how little it contributes, it undoubtedly produces significant savings and the ROI is better than anything else in the solar realm.
Click to expand...

You are in Texas, I am in Minnesota. I would think space heaters are more than enough down there, lol.

My NG furnace Draft Inducer fan died, of course on the coldest day a couple of years ago.

I had about a day and a half before I could get a replacement.

I ran three space heaters downstairs, and that was enough to hold 70 degrees in a older not so well insulated home of ~1,500 sq. ft.

Now, could those have reached 70 if it was much colder inside to begin with, probably not. But it was -20 outside.

Once my solar system is finished, I will definitely supplement furnace heat with electric from any excess generation.
 
Danke said:
I think someone posted here that under the recently passed bill, batteries alone also qualify for the 30%. Did you buy in 2021 or prior?

I’m kinda doubting power companies will be offering that deal after two years.
Click to expand...
This was a 2022 purchase which I essentially got an additional 4% off thanks to the 26 to 30% bump. However due to income limits on the home efficiency credits so I'm in fear of losing any and all credits going forward. Trying to get as much of this thing built this year before someone changes the law :).

I actually did some cursory numbers on the free nights plan with solar only and at the rate they gave me and based on my usage I'd be paying about $0.11/kWh without any battery or excess grid dump what-so-ever. So the free nights are almost worth it for solar only installs too as the lowest rate that is available in Texas now is around $0.15/kWh.

But yeah, I would assume if more people buy solar and batteries and chose to go with this plan, then yeah, it'll be a net loss for the power companies and will discontinue them. I'll enjoy the next two years then see what happens.
 
x98myers7 said:
a 1500w heater won't heat much more than an 8x10 room. that's a lot of juice for the amount of heat output.

you'd be better off investing in more insulation.
Click to expand...
this is purely supplemental heat. I have a propane fireplace downstairs that runs 24x7 and a electric forced air not on solar I try to run a little as possible.
 
Baseboard electric heaters can be run on DC as well as AC power. You don’t lose the inefficiency of putting it through the inverter and you don’t need as large of an inverter.
 
Chriskruger said:
Baseboard electric heaters can be run on DC as well as AC power. You don’t lose the inefficiency of putting it through the inverter and you don’t need as large of an inverter.
Click to expand...
question: what kind of wire are you going to run to run those DC baseboards? Unless you have high voltage DC at your house (most won't) and you're willing to run separate wiring with obscure voltages just stick to the basics and run the heat off of 120V AC. Again, if you're out in the wilderness where you're only building for yourself and adhering to no code, by all means do what you want but I would advise anyone in a city/suburbia setting to do anything this special, all in the name of efficiency.

Fun fact: the inefficiency turns into heat at the inverter so if you're thinking about running a DC heat to warm the place your inverter is in you're definitely wasting your time.
 
Diy geothermal cost me 6k after tax credit and that's with 2 wells drilled. Ohio doesn't get all that cold. Foam insulation is why my heating costs are low at 50 per month in winter. Now that I've added solar I will not have to use the grid at all. If temperatures get to zero I will just use my woodstove to supplement.
 
GregTR said:
question: what kind of wire are you going to run to run those DC baseboards? Unless you have high voltage DC at your house (most won't) and you're willing to run separate wiring with obscure voltages just stick to the basics and run the heat off of 120V AC. Again, if you're out in the wilderness where you're only building for yourself and adhering to no code, by all means do what you want but I would advise anyone in a city/suburbia setting to do anything this special, all in the name of efficiency.

Fun fact: the inefficiency turns into heat at the inverter so if you're thinking about running a DC heat to warm the place your inverter is in you're definitely wasting your time.
Click to expand...
The inverter is helping keep my basement at a good ambient temp of around 17C, I have a propane stove down for primary heat
 
nc73 said:
Diy geothermal cost me 6k after tax credit and that's with 2 wells drilled. Ohio doesn't get all that cold. Foam insulation is why my heating costs are low at 50 per month in winter. Now that I've added solar I will not have to use the grid at all. If temperatures get to zero I will just use my woodstove to supplement.
Click to expand...
I looked at it, we get real cold. The other option is a propane or electric element assisted heat pump I have heard of. Lots of research to do!
 
Redacted said:
I looked at it, we get real cold. The other option is a propane or electric element assisted heat pump I have heard of. Lots of research to do!
Click to expand...
If you have enough wells drilled, not affected by outside temps much.
 
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