Dumb question about electric boilers

MaxMercy

OK, it's almost New Years and most of us have some time off, so I thought I'd ask this now. I'm asking this in Connecticut where electric is so expensive that this might be the answer to my question, but what is the point of electric boilers? Resistance heating, although expensive, is 100 percent efficient at turning electricity into heat. I don't see how an electric boiler can improve on this, particularly when adding in the cost and complexity of the associated hydronic system. And even if electricity was somehow (or somewhere) cheap, how does an electric hydronic system equal the simplicity of baseboard resistance heating? I must be missing something here but I don't get it. Thanks.

ethicalpaul

It can't be improved on, as you say, because resistive heating is already 100% efficient.

That pales in comparison to heat pump technology which is about 350% efficient, but other than that, there's no magic.

It's probably cheaper and more efficient to send hot water to the rooms of a house than it is to send large amount of electricity to them...that's about all I can think of

GroundUp

The point of an electric boiler is to heat water which in turn heats a space. What's the point of a gas or oil boiler? Obviously, efficiency cannot be improved past 100% but electric is already there and gas/oil will never be there. Can you run baseboard, radiant slab, radiant walls, forced air, and panel radiators in the same house all with one appliance without using a boiler? It's merely a matter of preference. If you want in-floor heat in your garage and basement slabs on separate zones and electric rates make sense to do so, using resistance mats will work until they don't. Not if, but when there's a break in a cable, it's junk forever and cannot be used any longer nor can that break be found. Wires running everywhere make that a very distinct possibility and the cost of the mats greatly exceed hydronic anyway. With hydronics, the heat source can change, leaks can be found, it's just a cheaper, more reliable version of resistance heating. Electric boilers require almost zero maintenance, ever. The same cannot be said for gas and oil burners. Electric boilers are half the price of gas boilers upfront when talking smaller heat loads. In many parts of the country, utility companies offer dual fuel or off-peak rates making electric a very attractive option from an operating cost point of view. Low load spaces like small additions and garages may never use enough BTU to justify the cost and maintenance of a gas or oil boiler. I install a LOT of electric boilers here in MN because over a 20 year lifespan, most times they're still cheaper than gas boilers to do the same job.

JUGHNE

I am no big fan of electric heat, but it seems that electric BB heaters are a much cheaper install than copper tube BB.
And more efficient operation with individual room control.

One 20 amp 240 volt home run (12-2-G Romex) can feed 4 KW of BB heaters.
16' x 250 watts/foot will load the circuit up to 16 amps, 80% of a 20 amp circuit. 4000 watt x 3.413 = 13,650 btu.

The old quick and dirty rule of thumb for electricians used to be figure 10 watts per sq foot. So by that logic the above circuit could heat a 20 x 20 room. Giving you 34 btu per foot.
With today's homes that would guarantee more than enough heat in that room.
But with a wall tstat in that room one would have good control, short cycling not really an issue. Also giving quick recovery if needed.

Individual room control with copper BB is easily possible but requires a fair expense with zone valves or such.

And the energy source at the home is still electric resistance elements, whether in a boiler or in each room.
The only time the boiler seemed logical was if there was off peak power available from the utility. But with the light mass of copper BB heaters it seems you would not coast thru with some elements shut down.
Wet radiant in concrete floor would be the best for the off peak system, IMO.

Jamie Hall

Electric boilers -- or any other type of resistance heat -- are, indeed, 100% efficient. In terms of turning the electricity that reaches your switchboard into heat.

And that's where it stops -- and, apparently, where most people's thinking stops. Somewhere out there at the other end of the wires there is a power plant. If it is a thermal plant, it has somewhere in the area of 30% efficiency in turning the heating value of its fuel into electricity. Subtract another few percent in getting the power to you, and you might be still around 30% to be optimistic.

Now where is your efficiency? You burn oil in your home boiler -- 85% efficiency. You burn electricity in your home boiler -- 30% efficiency. You say but we can use a heat pump. At 0 Fahrenheit? Might be 350% on a nice day out, but not at that point. Even if it doesn't turn on its resistance heaters, it's still going to be around 200% -- so great. That gives the electric 70% efficiency.

I don't get it. I just don't get it.

jumper

Ceiling height radiant heaters are superior to baseboards in my opinion. For one thing floor level heat is easily obstructed. Too bad some women object to appearance.
Individual room control helps make electric competitive economically. In many homes most rooms are mostly unoccupied so 55° is acceptable.
If electricity is super cheap at certain times an electric boiler can heat water to high temperature and then one has energy storage.

EdTheHeaterMan

What if you like the feel of hydronic heat but live in an apartment with no ability to get gas, oil, or propane into your apartment or vent a fossil fuel heater from your apartment?   How would you heat the water for those radiators?   You can’t deny that a warm radiator is much more comfortable than an air duct connected to a heat pump.   

I think the higher temperature of electric resistance baseboard heaters are not as comfortable. It might just be in my mind, but sometimes you want what you want and that’s it.  

Robert_25

In my area electric boilers are usually found in old houses in towns with an agreement for cheap hydro power from Quebec.  Those houses originally had cast iron radiators and  coal or oil boilers, but electric boilers were retrofited in some of them.  No maintenance, quiet, and no fuel tank or chimney to worry about. As long as the rates are low enough and you have an electric service large enough it seems like a reasonable option to me.  I have actually considered a small electric boiler for my own house for a backup boiler.

Zman

If you want to have unlimited options headed forward, install low temp hydronic emitters. A good example would be a well designed hot water infloor radiant panel.
Once you have this in place you can change your heat source to anything from condensing boilers to solar to heat pump technologies.

Robert_25

Double post.

SlowYourRoll

not to mention...ever lose power in the middle of a blizzard?

mattmia2

I could see a retrofit or radiant heat, other than that, i see no advantage. you can get oil filled electric radiation with similar characteristics to hydronic emitters. I guess i could see it as emergency backup if you had the service for it or as a supplement to solar, geothermal, or an air to water heat pump when conditions exceed the capacity of the system

PerryHolzman

I'm also looking at a small electric boiler as a backup (to at least keep the house from freezing while the main boiler is being serviced).

I can clearly see them where you don't want radiators in each room for cosmetic or other reasons, and used warm water floor heating.

IF the cost of electricity is reasonable in the area it might indeed be cheaper and more reliable than installing and routine maintenance on a mod-con boiler over the years.

My wife and I have had several discussions about the cost of my Vitodens 200 retrofit into the house and its maintenance requirements and cost (even with me doing most of the work). The parts I installed earlier this year was noticeable (and the boiler out of service for days). I had the heating contractor in for a service call to replace the expansion tank, the auto-fill valve, and back-flow preventer, install an expansion tank isolation valve, and a pressure gauge. Lets just say that was not cheap either. So we have talked about the cost of installing and maintaining the system; and what are expected future maintenance cost are.

Would an electric boiler and paying the electric bill have actually been cheaper overall? Good question.

bburd

@PerryHolzman All of those parts you mention replacing are part of any hydronic heating system and would be required for an electric boiler as well.

ethicalpaul

Natural gas delivery losses—one of the great unknowns. My friend worked for PSE&G where there is a database of thousands of known leaks across NJ. They only fix the big ones, or the ones where people threaten to call the state regulators.

Right now there is one of those “chimneys” in the road around the corner from my house that vents the leaking gas a bit higher so passing cars can’t smell it as much.

There’s plenty of loss whether electric or gas.

https://www.scientificamerican.com/article/how-much-natural-gas-leaks/

https://www.greenbiz.com/article/natural-gas-production-releases-more-methane-estimated-why-matters

EdTheHeaterMan

Robert_25 said:

In my area electric boilers are usually found in old houses in towns with an agreement for cheap hydro power from Quebec.  Those houses originally had cast iron radiators and  coal or oil boilers, but electric boilers were retrofited in some of them.  No maintenance, quiet, and no fuel tank or chimney to worry about. As long as the rates are low enough and you have an electric service large enough it seems like a reasonable option to me.  I have actually considered a small electric boiler for my own house for a backup boiler.

That is a great idea! Having a backup heat source in case the electricity goes out for a long stretch. I might do that too!

psb75

Not understanding putting in a small ELECTRIC backup boiler in case the ELECTRICITY goes out. ??

bburd

You certainly won’t be able to run one off a house sized generator!

EdTheHeaterMan

psb75 said:

Not understanding putting in a small ELECTRIC backup boiler in case the ELECTRICITY goes out. ??

Sorry for the misunderstanding. That was a bit of Sarcasm. This is my official mask and it was my thumbnail picture until last month.

psb75

Sarcasm is hard to transmit esp. on a heating forum. Also tricky when folks often don't know each other--sight unseen.

jumper

Smart meters are coming. Unfortunately rates are not so smart. For example California often has surplus daytime electricity from solar but rates don't decrease until 10 PM.
Low cost electricity + energy storage is not new. Long ago cheap night time electricity heated ceramic furnaces.
For off grid locations least expensive storage is hot water. Are T&P safeties available for 250°?

ethicalpaul

I caught it @EdTheHeaterMan 😂

bburd

@jumper I live in northern California.  My home is on a PG&E time of use electric rate that is highest from 4-9 PM. 

Just as the sun goes down and solar power output drops to nothing, the dinner hour arrives. People start cooking on their electric ranges and using electrically heated water. That evening peak load beyond what nuclear and large hydro baseload plants can supply is filled mostly by natural gas fired peaking generation, the most costly power source on the system.

The off-peak discount is not much in the winter at $.03/kWh; but in the summer it’s $.085/kWh. The off-peak rate in the summer is higher than the on-peak rate in the winter; the summer cooling load is the biggest challenge to our system.

Robert_25

psb75 said:

Not understanding putting in a small ELECTRIC backup boiler in case the ELECTRICITY goes out. ??

My reference to a "backup boiler" was not in reference to something to use during a power outage, it is for a boiler that is hands-off if I need to travel for extended periods.  My main heating plant is a coal stoker boiler that draws a whopping 2.6 amps.  It is very reliable, but does need some attention every couple days. I also have a hand fired stove that doesn't require any electrical power.

EdTheHeaterMan

True Story!
My brother (later in life after selling a full-service retail fuel oil business to Sunoco) worked in sales for another fuel dealer in the Bucks County area of Pa. They were full service, sold and installed Air Conditioning equipment and also backup generators. With his vast experience in the industry, he became the "Go-To Guy" for all things unusual at the company.

After the devastating "Super Storm Sandy" the generator business was overwhelming. They could not get them installed fast enough.

As we all know in the HVAC industry, the 3 most common sources of heat are Gas, Oil, and Electricity. That said, one of the calls that were handed off to my very tactful brother was a woman (who's hair color is unknown) who was interested in an emergency back up generator. She did not want Propane tanks or Oil tanks on her property. There was no natural gas service to her property either. She wanted an emergency backup generator that worked off of electricity.

That is where I got the idea for the Backup Electric Boiler comment.

jumper

@bburd
I don't know how legal it is in California but it may actually be economical to install off grid solar with energy storage there. For heating I'd use quite hot water and for A/C I'd look for an ice maker. Hot water is much less expensive than batteries and should last longer than the house. You probably want an ice bin of several hundred cubic feet!

bburd

@jumper Trying to install such a system  in my seventh floor condo would be...interesting. 😎