Oil boiler vs electric boiler vs heat pump choices. Help needed!

J_Cov

Hello heating experts!

I have several problems I’m trying to solve for long term and I’m spinning my wheels looking for the best solutions. Sorry for the long post but I'm trying to get all the information out there.

Currently I have a 2400sqft ranch home in Southwestern CT with limited space for HVAC and well water equipment due to the fact the house sits on a crawl space. There’s a 150k btu oil boiler that feeds an indirect hot water heater and hydronic baseboard heat.
Both the boiler and hot water tank are on borrowed time and will need to be replaced sooner than later. I have a wood burning fireplace insert that keeps a few areas very comfortable on cold days but that heat can’t reach any of the bedrooms. The insulation is okay but could always be better. Blown cellulose in the attic.

The central A/C that lasted close to 20 years called it quits this year and I had it replaced with a Bosch 20 SEER heat pump that has been great and super efficient running A/C but I have no idea yet as to how it will heat the house. I had a heat pump 15-20 years ago in a condo and it stunk for producing heat but I think this newer Bosch will do better but by how much is questionable come January and February. It does not have a secondary electric heat backup.

So….I see and opportunity to get myself off oil here and possibly a few other benefits. I plan on adding Solar panels within the next year that can make going to a fully electric house attractive.
If I’m able to get rid of the boiler I’ll be able to add a much needed laundry room with a half bath and take out the chimney used by the boiler as well. That would be a huge win.

What I’m leaning towards is to replace the hot water heater with a Sanden ECO2 systems heat pump water heater. I like the fact that the heat pump is located outside the house so it will be quiet, but unsure if anyone can service it if problems come up. https://www.eco2waterheater.com/

Electric boilers do not seem a popular choice to power the hydronic baseboard heat, but I’m wondering if they could work for me. I’d like to have 3 zones (currently 2 zones) and adding a zone for the bedrooms would be ideal and the most used zone in the evenings. Would I have one larger boiler maybe a multi stage unit to power the zones or three smaller ones that would operate independently as needed?

Any tips or ideas would be much appreciated. I’ve been impressed with the professional input on this forum and look forward to the replies and if anyone is in the area let me know!

Hot_water_fan

Awesome level of detail here. A few questions:
1. How much oil did you use last winter? Fill ups dates, gallons and zip code would be helpful.
2. What's the size of the Bosch? Model number too would be helpful.
3. The Sanden is efficient, but very expensive compared to heat pump water heaters that aren't split units. How many people in the household? Do you use a lot of domestic hot water? I think eliminating the Sanden should be considered.

Briefly, it's entirely possible to go fully electric and get that additional space back. With the solar, you'll be able to offset much of your usage and oil is particularly expensive to heat with. The capacity of your electric panel will matter a lot. If it's 100 amps, it'll be a constraint. I'd spend the money upgrading that before going with the Sanden.
There is some finesse required when it comes to sizing: if the heat pump can't 100% meet the load on the coldest days, you'll need a backup: that backup could be:
1. existing oil boiler (takes up space, will need replacement someday).
2. Electric heat strips added to Bosch (will take up least amount of space and can be used during defrost cycles/ even during cooling season to help with dehumidification)
3. Electric boiler using existing baseboards (as supplement, not 100% of load). There are heat pumps that can be used with hydronic systems, they're just very rare in the US for now. Keeping the baseboards offers that option down the road if they gain traction.

Jamie Hall

Here we go again.

To take it from the top: unless you have a very large lot and want to cover it with solar PV panels, you will not be able to heat your house with solar voltaic equipment. You may, however, be able to install enough panel area to cover your electrical needs -- including the heat pump water heater -- when the sun is shining. This is not to be opposed to solar panels, but rather just plain vanilla physics. Sorry about that.

Electric boilers are not a popular choice for hydronic heat, at least in your region, for one very simple reason: they cost too much to run. You have some of the highest electric rates in the country, and it just doesn't compute. They are also not a particularly green option, as the overall efficiency of an electric boiler from fuel to the generating station to warmth in your house is about 33%, contrasted with a good oil or gas boiler which is about 85% and up to 96% in some installations.

An air to hot water heat pump may, possibly, be an option. They are about as efficient, in terms of overall fuel use, as an on-site oil or gas boiler. However, in my opinion at least there is still some question as to whether even the most sophisticated of them can really deliver on your coldest days. If you were to choose that route, you would do well to get a written guarantee that the system would heat your building to at least 75 F on your design day without using any secondary (resistance) electrical heat, with an additional guarantee that if it fails to do that the installer will replace it with a fuel fired boiler which will, at no charge to you. This will require the salesman and installer to put their money where their mouth is, as it were -- and you may find that they are unwilling to do that.

The heat pump hot water heater, however, is a good choice -- but there are a couple of comments there, too. They do require service. A lot more service than either a fuel fired or electric heater. If you have concerns about the availability and adequacy of service, this may be a deal breaker. The other thing to remember about them is that their recovery is slow, unless they switch to the electric resistance auxiliary heat which most of them have. This may or may not be a problem, depending on how much hot water you use and how you schedule it.

Depending on how much boiler you really need (you should do, or have done, a full heat loss calculation for your house) you may be able to use a wall hung, direct vented, natural gas fired boiler. These take up much less space than your existing boiler, and don't require a chimney. This might be a very good option, but do check and see if you can get natural gas service for it.

I'm truly sorry to be a bit of a wet blanket with regard to the combination of on-site photovoltaic solar power and space heating. While it is quite possible -- and, in my view, desirable -- for a new-build house to be entirely heated by the sun (I've built a few in my time), that is direct solar space heating, not photovoltaics, and it is simply not feasible to do that for an existing structure. Your existing boiler has a power input of about 44 kiloWatts. In direct, full, sunlight, that would require around 2200 square feet of solar panel -- or, very roughly, the total area of your house. The problem is, of course, that there are times when the panels will not be in full direct sunlight. Night time, for instance, or on a cloudy day. A very rough rule of thumb for your area is that you need about 8 times that area to gain and store enough energy to carry through the night, or a string of cloudy days -- or, in this case, around half an acre of panels. Plus, of course, the necessary batteries and converters...

Hot_water_fan

The heat loss is really the first step here: Say you heat loss comes to about 50k btu. That's about 15kw worth of solar, which is not much size wise on a rancher. That's if you use an electric boiler exclusively. If you use the Bosch, you can cut that in half or more. That's only 20 panels or so, which is about 300 sqft. You will not have to use batteries, you will use the grid at night. You also do not have to cover 100% of your electricity usage with solar (it's generally cheaper the bigger the array, but there are limits in terms of roof space).

The solar installation is almost independent of the heating decision: CT has high rates, so it'll be cheaper than status quo. The decision then becomes: 5kw or 10kw (just as an example).

EBEBRATT-Ed

I don't know what your time frame is. Either way i would get the heat strips for the Bosch AHU and get them installed. They are low $$ Upgrading the wiring to the AHU will be a larger expense.

Then you can try heating with the Bosh and shut the boiler down and try it before you commit

I wouldn't go with a heat pump for heating in the northeast but that's just me.

You already have a hot water system. I would put in the heat strips and a new boiler if it was me.

You can use the HP for heat say Sept, Oct & November &March, April and use the boiler the rest of the time

J_Cov

Thanks for responding Hot water fan and Jamie Hall! good stuff.

so more details...My yearly fuel bill has averaged $2400 per year over the last 5 years. Fill ups for the winter average every 5 weeks and roughly 400 gallons each time. After the winter is over its a fill every 2 months about 300 gallons each time. The wife and kids use a ton of hot water and the indirect tank is a solid performer working off the boiler. 5 people in the household.

The Bosch units: compressor - BOVA36HDN1M20G, air handler - BVA036WN1M20

I'm loving the Sanden unit for a couple of reasons one being the heat pump is located outside away from the tank so the noise is not an issue and also not creating any cooling from a stand alone standard heat pump powered hot water heater. The family room (a converted garage) is right next to the utility room and the boiler firing up requires a few up arrows on the tv remote.

The electric rates are sky high here in CT and that's motivation to get solar panels up there. Easy money to spend for a safe return. I'd put the max amount of panels up there and the estimate is I can fit a 20kwh system up there. Going with Tesla and our power company Eversource is giving a direct discount of roughly 35% off of Tesla's powerwalls which is very attractive. Given the storms causing havoc the last 10 years it would be nice to not need to wheel out the gas generator to power the house anymore.

I didn't plan on truly offsetting the electric boiler with solar but kind of ease the bite from using it as a backup if I could....Or even if I use it as a primary source I don't get crushed by it.

STEVEusaPA

I like multiple sources and backups & practice what I preach. My biggest concern about electric only and especially heat pump only, is a power outage, or a repair.
Say the power goes out or the unit quits, during a huge winter storm. By the time the tech gets there the outdoor unit could be completely buried/frozen.
The logistics to get a tech to the unit and shovel out where the controls rest or worse, the entire thing if you need to replace a motor would be a nightmare for me and I probably wouldn't service it Then you'll need to get all the frozen snow ice, off of the blades before firing it back up.
I strongly disagree with the statement "...oil is particularly expensive to heat with." And not just with the grammar.

ethicalpaul

My heat pump water heater is extremely quiet, does not noticeably cool the basement, and has required no service so far (two years). And it's so cheap per month it's almost free. I still can't believe people run oil boilers to heat their water in the summer.

Hot_water_fan

I strongly disagree with the statement "...oil is particularly expensive to heat with." And not just with the grammar.

How about oil, propane and electric resistance are particularly expensive to heat with?

Jamie Hall

Hot_water_fan said:

I strongly disagree with the statement "...oil is particularly expensive to heat with." And not just with the grammar.

How about oil, propane and electric resistance are particularly expensive to heat with?

Or perhaps we can just leave it that energy costs money... and it's not getting any cheaper...

I have to admit that I have a problem with the power company/state paybacks for solar power, but it's not on the basis that it's a Good Thing To Do. It's simply on the basis that while it is wonderful for those who can or want to do it, one does have to remember that someone is paying the bill for it, either through higher electric rates for them or through taxes -- or both -- and that that those someones do not always have the option to install the equipment on their properties... the rich get rich, and the poor get poorer.

Hot_water_fan

@Jamie Hall I totally agree - seems like that extends beyond just energy too.

Back to the matter at hand: basically that heat pump (a nice one by the way!!!) is not big enough to solely cover your heating load. However, it's efficient enough that it is worth running for the whole winter, especially with solar power. Therefore, you'll need 10 kw of supplemental heat (or so - check my numbers with this: https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new). Probably easiest to include it in the air handler, but the electric boiler option is doable too. So is keeping the oil burner, but you won't gain the laundry room, will keep the chimney, and you'll have to replace it one day. You can test it out this winter, set the heat pump's set point above the boiler's when it's around 30 degrees, and just shut the boiler down above that (for heating, not DHW).
I'd take a second look at a large, 80 gallon heat pump water heater, I think sound insulation is cheaper than a Sanden.
However, another twist is that if you go with a Sanden, it can be incorporated into the baseboards but it's limited to a small output I believe.

J_Cov

@ethicalpaul and @Hot_water_fan When you're right you're right....Sanden is out and a large heat pump hot water tank is in. I appreciate the help here fellas.

@Hot_water_fan That Bosch unit is awesome. I was lucky to have had my older Trane unit fail when it did. So given how it's tough to source any materials or supplies this year this unit was reserved for a new build but the builder fell behind schedule and it was one of the few available. I wasn't looking for a heat pump but to snag this unit I was all in. I don't have pro level knowledge (just enough to get in trouble) but the local HVAC contractor told me that this unit is variable from 3 to 5 ton capacity. He's going to install it on his own house. It's probably skimmed $20-$30 off the summer electric bill each month so far and it was hot this year.

@STEVEusaPA and @Hot_water_fan I forgot to stress the amount I use that wood stove insert. I split my own wood with the splitter and it can crank out the heat to the point I have fans on high to move the heat around as much as possible. Its a Boston enviro 1700. I looked up in the manual and the heat range is 9,425 to 31,780 BTU/hour (2,760 to 9,306 watt). Now it I'm hit by a bus I don't know if my wife will run it like I do but it does keep a portion of the house toasty. It's unfortunate that It won't reach the bedrooms (and the real need for a separate zone for them, especially at night). After the storms we've been hit with is was nice to have the Oil Burner and stove as back ups compared to a fully electric house. If I can hold my breath until the solar panels get installed and maybe limp around with them and a battery backup in case its an extended outage.


Also to note is recapturing the space in the existing utility room for a laundry and half bath will be a quite a savings as buildable space. Without any combustibles from oil It'll be safer as well. At roughly $300 a square foot I can get about 24sqft "back" from the 72sqft room which can be worth $7200,

Okay so where I think I am in the plan is

- 80 gallon heat pump hot water tank replacing the indirect tank that was oil burner fired. I'm curious, how many BTU's did it take from the oil burner?

- strongly consider the heat strips for the Bosch AHU and test if those can get the job done without the boiler.

Jon_blaney

Some observations and comments:

What is your priority? Save oil/money, be more comfortable or gain space? Put these in order of importance and the answers will follow

Heat pumps and wood stoves frequently don't work well together. You need to figure out how to get heat to those cold areas. Is your current system zoned? How about the a/c? Warm air systems work best when turn on and left on. You don't want the thermostat calling for heat when the living room is already a toasty 78 degrees.

The demand for how water is killing your oil usage. I would concentrate on this before heating the house.

Hot_water_fan

- 80 gallon heat pump hot water tank replacing the indirect tank that was oil burner fired. I'm curious, how many BTU's did it take from the oil burner?

Usually DHW gets priority. So the indirect would have taken 30%-100% of boiler output probably (this is usually customizable). However, it wouldn't be for long. For comparison, a gas tank heater might have a burner with an output of ~28kbtu to ~50kbtu. The heating capacity matters less considering you'll have 80 gallons as a buffer. The 80 gallon heat pump water heater from Rheem outputs between 4200 and 20,000 btu depending on mode.

J_Cov

@Jon_blaney - I did some thinking about what you've said and It's helped. In order of importance I'd say Gaining space, Being comfortable, and ditching oil. By going fully electric and getting rid of the oil boiler I do gain the space so that's the goal. Now what I can do to be comfortable 3 months of the year without oil is the concern.

Both you and @Hot_water_fan easily convinced me to replace the current hot water heater with a heat pump hot water heater. That's a great start and will be done soon.

The house has 2 zones for heat. The family room (converted garage) is one zone (about 20% of the home) and the rest of the house is the other. Ideally the bedrooms should have their own zone for a total of 3. For the A/C the house is all one zone and keeps the temperature constant throughout the house. That Bosch has been wonderful.

Because of the current zone split it' s a constant battle balancing the thermostat regarding heat. The wood stove can heat the middle of the home which is close enough to the thermostat where I need to set it to at least 78 to get the furnace to fire up. If I leave it the bedrooms will be 60 even with corner fans trying (and failing) to push the warm air to them.

Because of all of the above I found electric boilers attractive as a possible solution to getting heat to the hydronic baseboards. By only needing to cover smaller areas it may not be as costly to run if they run independently but I really don't know that. Uncharted waters

I've paper sketched the layout of the home and circled the 3 proposed zones. The middle Zone 2 can will be easily heated by the stove so that would see the least use but its the largest area. Zone 3 would be active during the day and evening as needed and Zone 1 for the bedrooms would be active at night.

Hot_water_fan

@J_Cov You can use the electric boiler with zones. Another option would be to replace the hydronic baseboards with electric ones. That'd be easiest to zone since each baseboard can come with its own thermostat. You're correct that the load for the bedrooms will probably be low, so the efficiency hit shouldn't be too bad. Another pro would be that each electric baseboard would be independent, so lots of redundancy. It would probably rule out ever switching to an air-to-water heat pump in the future though.

Jamie Hall

Hot_water_fan said:

@J_Cov You can use the electric boiler with zones. Another option would be to replace the hydronic baseboards with electric ones. That'd be easiest to zone since each baseboard can come with its own thermostat. You're correct that the load for the bedrooms will probably be low, so the efficiency hit shouldn't be too bad. Another pro would be that each electric baseboard would be independent, so lots of redundancy. It would probably rule out ever switching to an air-to-water heat pump in the future though.

One might find it hard to believe, but I have used electric baseboards in one of the places I care for. Now I'll grant that it's three and a half seasons (the water supply would freeze) instead of four, and they do suck up a pretty fair amount of power on a cold day -- but the ease of installation and low first cost, plus the ease of zoning (I have wall mounted 240 volt thermostats in each room) is really wonderful.

leo95se

hi @J_Cov did you install your hybrid hot water heater? Curious to hear feedback.  Thanks!