Oil to Electric options to keep hydronic baseboard?

darkmatter762

I have an old Oil-fired System 2000 hot water and hydronic baseboard heating system. I want to get off Oil eventually, especially as I just installed solar power at the house. So I am looking to power my hot water and heating needs with electricity, despite how inefficient electric resistance heat is compared to oil.

Is there a way I can keep my 11-zone hydronic baseboard system and just heat the water with an electric resistance boiler/tank? As well as provide domestic hot water?

I've Googled this for days and have not found a perfect solution yet. I have considered geo-thermal and heat-pumps, but that would require putting in new ductwork as well.

Appreciate any ideas here.

delcrossv

If you already know it's inefficient, why do it?

hot_rod

what’s what supply temperatures do you need? Air to water heat pump might work. Or hybrid it, heat pump with oil back up for high load conditions
How many KW of PV?

bburd

There are electric resistance boilers, but they only make financial sense where electric rates are extremely low; and you would almost certainly need a much larger electric service than you now have.

Unfortunately the greatest heating load does not coincide with the greatest output from your solar panels, and in most places the very favorable “net metering” arrangements that have been common for years are going away.

Jamie Hall

The ONLY option which really makes sense at all is an air to water heat pump, and they only work if your baseboards will run at low temperature -- 140 or so.

There are electric boilers available -- quite a number of them, in fact, and they work well. You'll want to do the math on running costs; it isn't possible to make a generalization on relative cost, since electric rates vary so widely depending on where you are.

I'm not sure what you mean by electric being inefficient -- an electric resistance heater will convert all the kilowatts you feed it into heat, 100%, although the power plants that feed the grid are much less efficient (33% or so) than your oil burner is.

You cheerfully mention that you now have solar power at the house. As was asked, how many KW installed power, and what is your battery capacity? A good rule of thumb in the northeast is that you need to have enough battery capacity to power your house for 3 days (72 hours) without charging and enough installed solar panel capacity to charge those batteries in nine hours. Other parts of the country are not so cloudy, and so you may need less. Otherwise while your panels are a nice virtue signal, they aren't much help in keeping you actually warm.

Hot_water_fan

An air to water heat pump (connects to the baseboard, no ductwork) is your best bet- possibly in a hybrid situation with oil as backup. Solar electricity will be much cheaper than oil . You don’t need batteries, but perhaps you may want them.

GroundUp

I'm going to go against the grain here and answer your question instead of trying to make suggestions you didn't ask for.

No, there is no combination electric boiler/water heater available. Yes, you can use one or the other with a heat exchanger to perform both functions assuming the proper sizing and piping. No, that wouldn't really make a lot of sense. An electric boiler to replace your oil boiler, and a separate electric water heater (possibly a hybrid HP if you so desire) for domestic water are the best bet to maintain your hydronic baseboard system with an electric heat source.

STEVEusaPA

darkmatter762 said:

...So I am looking to power my hot water and heating needs with electricity, despite how inefficient electric resistance heat is compared to oil...

lmfao

Jamie Hall

On electric boilers for home heat. A ten second search found these:

https://www.supplyhouse.com/Electric-Boilers-1738000?utm_source=bingad&utm_medium=dsa&msclkid=e24b90c5eb4119676f8df2effad9d4e4

Good luck.

Roger

@darkmatter762 , it would be helpful to know what you have as a goal.
It would be very surprising if you had enough solar PV to cover even a small portion of the winter heating load with electricity. Many states limit the size of solar PV installations relative to your historical electricity usage, but there are often loopholes to install more. Hot water in the summer may be a different story, although you are likely using less than 1/3 a gallon of oil per day for hot water in the summer with System 2000 (probably about 10 kWh equivalent with electric hot water, or $2/day electricity at $0.20/kWh without sunshine; and $1 per day for oil at $3.00/gal*), so payback is a challenge even with available PV.
If your goal is using your new source of electricity for heating, it is likely not enough for the winter.
If your goal is reducing carbon intensity, fuel oil frequently has biofuels blended in already and there are many liquid heating fuel (oil) companies offering higher blends levels.
*I used $3/gal as for future reference to this post, prices are higher today; electricity rates generally reflect natural gas pricing in the long run.
Roger

fentonc

What air-to-water heat pumps are actually available in the US? My baseboards would probably be fine down to 130F or so at the design temp, but I've never seen any of the companies around here mention them as options (NY area).

Jamie Hall

Carrier, Mitsubishi for fwto

darkmatter762

Thanks for the responses here, I appreciate the help. A few answers & additional details:

• House is 3,750 sq ft, built in 1980.
• I have a 12kW solar roof plus 2 13.5kW Powerwall batteries, recently installed, so I don't have a full years usage history to know all the metrics
• I am getting usable sunlight from ~6am-6pm here in NJ right now
• I was able to get the batteries charged from 22%-100% in about 9 hours, but still haven't had a solid sunny day here yet.
  
• My oil tank is 275gallons capacity
• Since Oct 30th 2021 I have refilled the tank 7 times, for a total of 1257.4 gallons. In today's money it's about $1000 per 200 gallons.
• I used the wrong word "efficient" in my original post. I meant I had heard that heating a house with electricity is more expensive than gas/oil due to how hot those forms of fuel combust in comparison
• I am not looking to power my heating needs entirely from solar, as I agree it is not powerful enough, especially in winter time. But perhaps using electricity from the grid plus my solar to offset a little would still be a good goal to reach for.

So perhaps air-water heat pump might be the best direction to go in for hydronic baseboard & radiant floor heat. And then a hybrid electric/heat pump water boiler combo unit for domestic hot water.

Jamie Hall

Well, let's do some number crunching here. Your oil consumption is around 10 gallons per day, on average, which is -- allowing for combustion efficiency -- around 1,130,000 BTU per day. That's about 360 KWh per day. On average, in the northeast, you can get somewhere around 4 hours per day of usable sunshine -- so your solar panels can produce about 50 KWh per day of energy, of which you can store 27 (I presume you meant that those Powerwalls are 13.5 KWh each -- the measure of energy -- rather than 13.5 KW, a measure of instantaneous power). This brief exercise in number crunching indicates that, on average, you couldn't heat your house -- even with a heat pump -- for more than a few hours once the sun went down from the batteries. Your solar panels could power a heat pump, on average, however -- but only when the sun was actually shining.

Such are the tough numbers of physics. Sorry about that. As you note, however, it might be worth using that solar capacity to offset some of the power draw of the heat pump.

Cost is another matter, of course, and is quite dependent on what your utility or oil supplier charge you, and has remarkably little to do with real physics or engineering.

Roger

Thank you for your post, @darkmatter762 .
Your home is using much more fuel than I would expect for the size you mentioned with 1980's construction in NJ. The building shell and system operation should certainly be reviewed.
New Jersey is a net metering state, so power you generate is effectively credited back at the residential electric rate. At $0.17 kWh, that's almost $7/gallon of oil.
An additional consideration is that in rough terms, you'll generate about 1,200 kWh per year per kW of installed solar in NJ. That's 14,400 kWhs/year, or the equivalent of about 350 gallons of oil in total.
Just food for thought if you're interested in cost savings; again biofuels may be a better option if you're interested in reducing carbon intensity.
Roger

Hot_water_fan

@darkmatter762 sounds like you’re on the right path! Air-to-water could also be used for both domestic hot water and heating, so you won’t necessarily need two systems.  You might not find it useful to cover 100% of your heating loading with the heat pump and that’s perfectly fine, as you have a boiler already. With the cheap solar electricity, you’ll be spending much less on fuel if using a heat pump vs. oil. The solar/battery capacity discussion is interesting, but not relevant to your goals. The solar and battery size matters if you’re trying to power the house without the grid, which as noted, isn’t going to happen when it’s very cold as things currently stand.

I used the wrong word "efficient" in my original post. I meant I had heard that heating a house with electricity is more expensive than gas/oil due to how hot those forms of fuel combust in comparison

You heard wrong - nothing to do with the heat of these fuels. Sometimes oil/gas is cheaper than electricity, sometimes not, you’ll have to figure it out for your situation using these calculations. 

The equation output $/MMBtu for oil is: $/gallon x (1,000,000/138,000) / COP.

for electricity: $/kwh x (1,000,000/3412) / COP.  

darkmatter762

Roger said:

Thank you for your post, @darkmatter762 .
Your home is using much more fuel than I would expect for the size you mentioned with 1980's construction in NJ. The building shell and system operation should certainly be reviewed.
Roger

Thanks Roger. I've just emailed your company to have those numbers reviewed and maybe someone can help suggest a good service provider to do an inspection of the system.

Hot_water_fan

At $0.17 kWh, that's almost $7/gallon of oil. 

This is half of the story. This is cost per BTU input not cost per BTU output. @darkmatter762 you care about BTU output. $.17 x 293 / 3 = $16.6/ MMBtu for electricity. 

That’s equivalent to $1.94/ gallon of oil.

I’m with Roger, that’s a ton of oil for a NJ house of that age. 

EdTheHeaterMan

I have seen some Weil McLain Cast Iron Electric fired boilers. I was very impressed with them, but they no longer have them in their current catalogue. They were individual boilers for an apartment house (4 unit) so each tenant paid for their own heat.

Try this company
https://www.ecomfort.com/heating/electric-boilers.html

With Solar, I can understand wanting to go Electric. But if the power goes out, it might be nice to have that oil heater available. That way you won't be using up your backup batteries or backup generator capacity. Is it cheeper to make heat from the boiler than it is to make enough electricity to operate the electric boiler from a backup generator?

Mr.Ed

Jamie Hall

Hot_water_fan said:

At $0.17 kWh, that's almost $7/gallon of oil. 

This is half of the story. This is cost per BTU input not cost per BTU output. @darkmatter762 you care about BTU output. $.17 x 293 / 3 = $16.6/ MMBtu for electricity. 

That’s equivalent to $1.94/ gallon of oil.

I’m with Roger, that’s a ton of oil for a NJ house of that age. 

I respectfully disagree with the math... unless that 3 in there is the COP of the heat pump.

Hot_water_fan

I respectfully disagree with the math... unless that 3 in there is the COP of the heat pump.

Indeed it is . 

EdTheHeaterMan

If you do go with an electric boiler as the primary heat source, DON'T throw away that EK boiler. I'm assuming you would keep it connected and have the ability to fire it up as a backup heat system. Some manual valves are easy to install to isolate the boiler(s) from each other. Folks have been doing that with wood stove boilers for years. I'm a gadget guy so I would figure out some electric valve actuators with a switch that has options like Electric - Oil ...and... Winter - Summer. But thats just me

kcopp

It would be simpler to just move....

TAG

oil is just expensive right now ..... for quite a while it was cheap. My new house in PA used 1500g of propane last year ... it's a bit bigger w/ foam. My last was about your size and oil --- used about the same in oil. I was also oil water heater for domestic

Robert_25

darkmatter762 said:

Roger said:

Thank you for your post, @darkmatter762 .
Your home is using much more fuel than I would expect for the size you mentioned with 1980's construction in NJ. The building shell and system operation should certainly be reviewed.
Roger

Thanks Roger. I've just emailed your company to have those numbers reviewed and maybe someone can help suggest a good service provider to do an inspection of the system.

You should also have an energy audit done on the house. That is a lot of heating oil - the BTU's are going somewhere. For comparison, my house requires about the same amount of BTU's - but I live 5 minutes south of Quebec in a 100+ year old house.

In_New_England

darkmatter762 said:

Since Oct 30th 2021 I have refilled the tank 7 times, for a total of 1257.4 gallons. In today's money it's about $1000 per 200 gallons.

That seems like a LOT of oil consumed. That is about 139000 BTU/gal * 1257.4 gal = 174778600 BTU
over 5 months. Which is an average of 174778600/(5 * 30 * 24) = 48549.6 BTU/Hr

Now, for design day losses in New England, I would believe this, but on average, it's pretty high, even for a 3,750 sq ft house, especially built so recently and in NJ, which I think is milder than, say, Boston.

It could be that the oil burner is very inefficient. With a 60% efficiency that comes out to 29129 BTU/Hr which I can believe, but I wonder if a first priority should be insulation.

EBEBRATT-Ed

@darkmatter762

The first thing you should do is an energy audit of your house and find out where the heat is going. Tighten the envelope, windows , insulation, caulking etc. Then you will save $$$ no matter what fuel you use.

Dave Carpentier

Ya, I think that amount of oil shocked everyone, including me.
My design temp is -21f here (brr) , 2600 sqft above ground and only moderately sealed, and we use around 500-600 gallons of oil (80% eff boiler).

In_New_England

I don't know if anyone has mentioned it, but there are companies in Europe trying out high temperature air to water heat pumps that can be drop in replacements for gas/oil boilers for high temp baseboard systems.

The web search term is "High temperature air to water heat pump."

I don't know when this will come to the US.

hot_rod

Space Pak Solstice Extreme is a low ambient A2WHP made in the US. They have been pioneering this technology for 10 year or more. Installations all over the New England area. 120F supply is the sweet spot. So you need heat emitters that can cover your load with 120swt. Radiant, panel rads, and air handlers with properly sized coils 
several other US brands and 5 or 6 cold climate brands manufactured in Canada

JakeCK

I would really love to install a a2w hp at some point. Rarely do I see water temperatures above 120f and usually only for a brief time at the end of a cycle. 

A large buffer tank with a HP for the milder days and to decouple the boiler from the houses heating load would make for an incredibly efficient system I have think. 

hot_rod

JakeCK said:

I would really love to install a a2w hp at some point. Rarely do I see water temperatures above 120f and usually only for a brief time at the end of a cycle. 

A large buffer tank with a HP for the milder days and to decouple the boiler from the houses heating load would make for an incredibly efficient system I have think. 

The latest inverter drive units work fine with much smaller buffer tanks, as they modulate to the load.

426hemi

You do understand the amount of current required to heat your house with electricity right? To replace a typical 500k btu boiler your looking at 150kw! Assuming you have standard single phase 120/240 200 amp service it’s impossible as the current draw is going to be over 600 amps at 240volts! Your certainly not running it off some solar panels. Maybe you have a hydroelectric dam or small nuclear reactor we don’t know about 

Hot_water_fan

@426hemi the typical 500kBtu boiler in a NJ house? Ha!

cowdog

You have better savings converting from oil to wood or coal.