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I am looking for advice on how to get hot water if I remove my current central heating system for an electric system.

Current system

I live in an old 4 bed property built 1800s. I have an oil fired hot water and heating (vented) system, but both the oil tank and boiler need replaced (20+ years old). The property has two bathrooms with two electric showers.

New sytem

I am thinking about going all electric (I know the prices are increasing, so bare with me) by removing the oil tank and boiler completely and replacing all radiators / rails with wifi connected electric (oil filled) radiators

I'd like to do that, but I'm not sure what to do about hot water i.e. for a bath (a rare occasion) and for the sinks

Idea 1:

For the sinks (3-off), I was thinking about installing under the sink water heaters, which means I get instant hot water from the three of them and the hot water doesn't need to travel so far across the house.

For the bath, I was thinking about just keeping the hot water tank and using the immersion heater any time I want a bath - not very often. It's an indirect vented cylinder, so I'm guessing as part of removing the radiators and boiler, we could just cap off the flow pipes from the boiler to the cylinder?

Idea 2:

The alternative is that I just replace the indirect vented cylinder with a direct vented cylinder and heat the hot water that way. But that seems a waste of energy given how little hot water I use (we have electric showers and use a dishwasher for dishes).

Question

Which idea do you think would be more energy intensive?


PS One of the reasons I am also removing the oil fired system is that I live in a remote location, and it's so difficult to get the system serviced / maintained. There are two of us in the property and it is well insulated.

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    Do you have enough capacity in your panel for all electric heat? It takes a lot. A heat pump system will probably be much better for your electric bill.
    – crip659
    Jul 26, 2022 at 13:52
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    Had an electrician here last week who said we had enough capacity.
    – gelviis
    Jul 26, 2022 at 16:24
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    Get an HVAC specialist in to make suggestions.
    – FreeMan
    Jul 26, 2022 at 18:17
  • What country? UK are about to ban gas & oil heating on new installs [from 2025, though you will still be allowed to replace existing systems]. Heat pump all the way now. My parent's new build [though of course it has underfloor] is entirely heat pump, no gas in the house at all. Hot water comes off it too.
    – Tetsujin
    Jul 26, 2022 at 18:24

1 Answer 1

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I can't answer the hot water heating so easily. But do not go with your current plan for space heating.

TL;DR If you're going to switch to electric heat, get a modern heat pump.

Background:

With some unusual exceptions, most modern (last 100 years+) space heating systems for small buildings are one of the following:

  • Burn fossil fuels to heat water, transport hot water throughout the building
  • Burn fossil fuels to heat air, transport hot air throughout the building
  • Electric resistance heaters in individual rooms
  • Electric resistance heaters to heat air, transport hot air throughout the building
  • Use electricity to pump heat from outside to inside (exact reverse of air conditioning which pumps heat from inside to outside)

The first system (you have a variant of that) is one of the older types (though modern versions are available). It has the advantage of working with minimal electricity (thermostat, controls, etc.) or possibly no electricity at all. If powered by oil, it has the advantage of being self-contained (no natural gas supply needed). But there are disadvantages too, and they are gradually disappearing.

The second type is extremely common in the US, generally powered by natural gas piped in via a utility. This can produce a lot of heat very quickly (feels great!), but generally requires a natural gas line or a propane tank. The air handler requires a moderate amount of electricity, but not all that much, and the air handler also doubles as part of an air conditioning system in the summer. These systems have become more efficient in recent years, with new systems more than 90% efficient.

The third and fourth systems are almost the same. Electric resistance heat, whether simple baseboards, room-size units with fans, portable plug-in heaters, or whole-house systems connected to ductwork (which from the user perspective are little different from natural gas furnaces), is also nearly 100% efficient in converting electricity to heat. This seems ideal (until heat pumps) except that are significant losses in producing electricity (which is often from fossil fuels) and in transmitting electricity long distances. As a result, the cost effectiveness of oil (usually boiler) or gas (usually forced air) heat vs. electric heat has varied over the years and by location. Where electricity is relatively cheap (typically in nuclear or hydro areas), electric resistance heating can be less expensive than high-efficiency gas heating. Where electricity is more expensive, burning the fuel locally with an efficient system will generally cost less.

The last type is the newest. Heat pumps have been around for a long time, basically as long as air conditioning. Actually, modern refrigeration is really a miniature heat pump, but except for big commercial units (walk-ins) with the heat going from the inside of your refrigerator to your kitchen (great in winter, not in summer).

The beauty of heat pumps is that they have become incredibly efficient, and the hardware is not that much more complex than an air conditioner. A heat pump works both directions (heat in to out and out to in) instead of the single direction of an air conditioner (heat in to out). Older heat pumps did not handle relatively cold weather very well, so they come with "emergency heat". That emergency heat can be a full natural gas furnace, but unless you already have that in place, the usual solution is electric resistance heat because it is very low cost to buy and install.

In the old days, heat pumps were not used much in northern parts of the US because they could not handle cold weather (e.g., 20s F) very well. When the outside temperature gets too cold, a heat pump won't work well (if at all) and falls back (typically) to the relatively expensive to run electric resistance heat. If you need that emergency heat a lot of the time, there is little point in bothering with a heat pump as a natural gas furnace will cost less to run.

However, today's more efficient heat pumps (a) can handle much colder temperatures, so the emergency heat is rarely needed if the right system is installed for your climate, and (b) have gotten so much more efficient that they not only save a lot of money when running than electric resistance heat, but they save a lot of money (=power, fossil fuel, CO2 emissions, etc.) compared to the old standard of high-efficiency natural gas furnaces.

"electric oil filled radiators" produce a more even heat than "giant toaster baseboard heaters". But the power in/out is exactly the same. Which is 100% efficient for direct electricity usage but far less efficient compared to moving heat from outside to inside.

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    Are today's heat pumps able to heat water enough to drive hydronic heating, which OP already has?
    – jay613
    Jul 26, 2022 at 15:04
  • If you choose to go with a heat pump for an 1800s house you should also look at replacing all your radiators and pipework with a high velocity air handler. (Spacepak, Unico ... look it up). It's an expensive installation but makes good use of the limited space in an older house.
    – jay613
    Jul 26, 2022 at 15:07
  • @jay613 As far as I know (but then again, in UK (based on "electric showers", among other hints) they may have heat pumps that can heat water. But I wouldn't count on that. OP is talking about dumping the existing setup altogether. A multiple head split system might make a lot more sense than installing ductwork. Jul 26, 2022 at 15:30
  • One of the local plumbers said he didn't think a heat pump would produce enough power for heating the house. Based on some Google searches, there are some hot water only heat pumps, but seems like newish technology - or maybe just not common. Thanks for the reply.
    – gelviis
    Jul 26, 2022 at 16:29
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    To a hammer, everything looks like a nail. To a plumber (unless they also do general HVAC including forced air systems, heat pumps, etc.) everything looks like a water pipe - they go with what they know. Jul 26, 2022 at 16:34

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