Electric water heater?

JordanCT

New Member
Oct 16, 2018
15
CT
I’m looking for ideas and insights. I currently have solar panels, wood stove, and oil furnace/boiler with baseboard hot water. The solar panels over produce significantly, the wood stove is our main/only needed heat source in the winter, which means the oil furnace is basically just making hot water for cooking and showers. I am thinking that an electric hot water set up might be a more efficient and cost effective means of producing hot water. We would like to keep the option to run heat through the baseboard during winter vacations. Would an electric hot water heater be sufficient for this? Or would I need to keep the ability to use the oil furnace for this time? Thoughts, suggestions, recommendations for types/models of hot water heaters? Thanks!
 

Circus

Feeling the Heat
Jan 11, 2013
289
EC Wisconsin
Boilers usually run at about 180::F, water heaters 120::F so using a boiler just heating hot water is wasteful. Specially when not heating. I suppose you can pump water from a water heater through the baseboards but you wouldn't get much heat. Probably good enough to keep them from freezing. Check the design pressure of the baseboards.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,241
SE PA
The easiest option here is to:

(1) Buy an heat pump water heater (HPWH), which have really matured over the last several years, and use only about 33% as much energy as a conventional electric tank. I think CT has great incentives on HPWHs right now...might get the unit at a steep discount.
(2) Keep the boiler (for your desired backup) and leave it cold all summer.

Questions:
--On the HPWH, they can be loud, tall, and steal space heat from the room they are in. So you need to be able to site them somewhere where this will not be a problem. If you have a large family (or ar HW super users), you will want to get a 80 gal unit (IMO), which is more expensive than the stock 50 and 60 gal units, bc the recovery time when HW is used up can be a several hours. Some people fear that HPWHs don't pencil out in very cold climates. I am skeptical of that, esp since your space heat BTU are cheap (wood).
--Some older boilers will not be happy sitting cold for long periods (can rust out). If it is near the end of its life, or starting to leak a little, etc, this plan **might** hasten its demise. Conversely, most boilers will be aok with this.
--Some creative types think about putting the boiler and HPWH in series or something weird. Don't. I wouldn't even pay for the plumbing to have the option to switch between them. Just put in the HPWH, start burning some extra solar kWhs, and disconnect the boiler from the HW supply (ditching a mixing valve and other junk).
--Longer term, you could look at mini-splits for providing heating backup, or a whole house heat pump, depending on your climate. That and electric cars are common ways fo dealing with excess solar production. Of course CT elec rates are stupid expensive (my sis works at the elec company there) so that doesn't help elec pace heating.

--You can decide to run the boiler on standby in the winter or not, depending on several factors. My boiler burned more than a gallon of oil on standby per day. This had the effect of heating my house by 6-10°F above ambient. This drove up my AC bills a LOT (bc I would be running AC when it was not that hot out), but kept my furnace room (the wall of which was left uninsulated in 1960) nice and toasty. So obv you don't want that heat in the summer. But in the winter, if you leave the boiler off, your basement might get really cold, floors get colder, your wood consumption will go up, and the shoulder season might become longer. So, if you leave the boiler, you can decide to leave it hot on standby if any of those things are a problem, for a couple bucks a day. When I tore my boiler out, I ended up insulating that wall, and dropping a HVAC supply to that space. YMMV.
 
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SidecarFlip

Minister of Fire
Though not the norm, I heat my entire shop (40 x 60) with in floor PEX heated with a propane fired HWH and have for years. I have a bulb type thermostat in a well drilled in the concrete floor and epoxied in. The floor temp stays at 70 all winter. Nice and toasty. It's closed loop with a circulator pump and the T'stat controls the pump and the HWH runs when the fluid calls for hear. I never fool with it except in the summer I switch off the pump. Run RV antifreeze in the system.
 

peakbagger

Minister of Fire
Jul 11, 2008
5,523
Northern NH
Yes it can be done for heating but you will need a heat exchanger and preferably an outdoor reset controller to control the water temp being circulated. Ideally you only circulate the temperature needed to keep the place warm and on 50 degree day that may only be 80 degree water. The heat exchanger is to to keep the water being used for heating away from the hot water heater internals unless you never plan to heat potable water with it. You also need to isolate the boiler out of the loop as otherwise the hot water being circulated will go through the boiler and give up heat through the heat exchanger that then goes up the stack. As noted many older cast iron boilers will start to leak if stored cold. Its a hit or miss issue, my Crown cast iron boiler has been used in similar service for over ten years.

A much better alternative is install a high efficiency mini split for heating. If the place is in CT, your Coefficient of Performance (COP) will be quite high and its likely you can get a rebate on it from the utlity. A guess is over 3. That means that for every 1 KW of solar PV you generate you get 3 KW of heating. I do a sort of similar approach with my minisplit and use net metered surplus electric power to run my minisplit during shoulder heating seasons as my only heat source. I am well north of you so I switch over to my wood boiler during colder weather but it cuts down on a lot of hassle and wood use for free. I am dong it today where the overnight temp was 30 degrees but it supposed to warm up to 55 degrees. I even have AC for free during the rare but increasing times in the summer when I want it. I carry about a 2500 KW surplus going out of fall and time the minsplit use so I dont run out of surplus in April, then I build the surplus back up again until October. I do know folks with ski camps up here that have just a minisplit to heat their places during the week. They typicially have a few electric baseboards installed in key locations like the bathroom and keep them set low to keep the pipes from freezing in an extended cold snap. There are devices that run the curculator pumps every so many hours to keep water from freezing in cold spots in the pipes, depending on how you piing is set up you may need a couple of them.
 
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woodgeek

Minister of Fire
Jan 27, 2008
4,241
SE PA
I would say that the COP of modern HPWHs is also about 3.0, like a minisplit.

I found that my oil boiler when I stopped using it for space heat was burning 70% of its oil in standby. Like a COP of 0.3, counting 80% eff makes that 0.24. So every BTU of electricity I put in my HPWH replaces 12 BTU of fuel oil I was putting in my boiler before, for the same water output.

It will come down to things like if OP has room for a HPWH or a minisplit, or both. Whether he wants more AC in the summer, or basement dehumidification (a side bene of HPWH), how big his excess is, etc.

And I did have my circulation freeze a couple times, way down here by the Mason-Dixon line (15 miles from me). I was shocked, but I guess a lot of the runs are really near the sill plate, and they get cold drafts. The piping is usually heavier gauge than potable water, so it didn't burst....but kinda annoying when I DID want to circulate some heat....only to find the loop plugged with ice!
 

Circus

Feeling the Heat
Jan 11, 2013
289
EC Wisconsin
Which type? It all depends on how much hot water you use. It's hard to beat a simple electric hot water heater if you use very little hot water. They're cheap, simple, reliable and there's no heat sucking flue. Uses more electricity per gal. You'll have to figure out if you'll ever recoup the added expense of a heat pump. Either is better than using a boiler to heat water. If only to get rid of the flue.
 

Rob711

Feeling the Heat
Oct 19, 2017
351
Long Island, ny
I’m creative and weird! I started a thread on putting one before my new natural gas HWH. I like that I can have hot water if we lose power. It would look like a total cluster f.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,241
SE PA
I had a 1994 vintage Slantfin. I improved the insulation on it, but it still sucked on standby. The prices have come down on HPWHs, and the rebates are great I think in CT. I kept my two teen daughters in hot water for their teen years with one...no regrets.

As for power outs.... I have an 80 gallon unit, and it stays hot for 4-5 days without power. I just take quick showers a bit less often, and have not run out. If I wanted to get cute with a nat gas heater, I'd pipe it in parallel not series, with valves. Parasitic losses on a gas HWH are awful.
 

Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
Those HPWHs are very expensive compared to a standard electric water heater. Do they pencil out with respect to ROI? What is the break-even time on the cost difference? Additionally, from a green perspective, when you look at the complete product life cycle, from fabrication to recycling, is it a more environmentally friendly and overall cost effective solution?
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,399
NE Ohio
Those HPWHs are very expensive compared to a standard electric water heater.
Not so much anymore...I bought one for ~$300 more than a good electric resistance water heater
 

Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
Not so much anymore...I bought one for ~$300 more than a good electric resistance water heater
That may make more sense. When I took a quick look at HD, a Rheem resistance WH was $420 and a HPWH $1,300, about 3X the cost.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,241
SE PA
At the high prices of elec in CT, I am sure it pencils out.

The hardware is not that complicated....its just a compressor not that different from what is on a refrigerator...and those can run for decades.

.

This article says operating costs on a electric HWH is $780/yr (at $0.18/kWh). At COP =3, that is $500 savings per year.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,399
NE Ohio
This article says operating costs on a electric HWH is $780/yr (at $0.18/kWh). At COP =3, that is $500 savings per year.
We are about $0.118 cents per kWh (all in) here...I think I'm saving $15-20/month...
 
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Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
We are about $0.118 cents per kWh (all in) here...I think I'm saving $15-20/month...
With only a $300 delta, that would be an easy decision. Is the air going through the evaporator coil being used to cool something??
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,399
NE Ohio
With only a $300 delta, that would be an easy decision. Is the air going through the evaporator coil being used to cool something??
Its basically dehumidifying the basement...I didn't have to use the actual DH at all this summer...and the HPWH is about 10-12' away from my wood furnace, so when I light that off the "waste heat" going to the basement raises the ambient air temp about 10*...has to help the efficiency on the HPWH some...
 
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brenndatomu

Minister of Fire
Aug 21, 2013
5,399
NE Ohio

Brian26

Minister of Fire
Sep 20, 2013
508
Branford, CT
I’m looking for ideas and insights. I currently have solar panels, wood stove, and oil furnace/boiler with baseboard hot water. The solar panels over produce significantly, the wood stove is our main/only needed heat source in the winter, which means the oil furnace is basically just making hot water for cooking and showers. I am thinking that an electric hot water set up might be a more efficient and cost effective means of producing hot water. We would like to keep the option to run heat through the baseboard during winter vacations. Would an electric hot water heater be sufficient for this? Or would I need to keep the ability to use the oil furnace for this time? Thoughts, suggestions, recommendations for types/models of hot water heaters? Thanks!
CT has a $750 instant rebate on heat pump hot water heaters at Lowes and Home Depot. That is like 75% percent of the cost and makes it cheaper than even a standard electric tank. Just walk into any Lowes or HD and its automatically deducted.

CT is giving out money like no tomorrow for energy efficiency upgrades through its energizect efficiency program. Check out energizect.com.

The state also just tripled its mini split/heat pump rebate form $500 a ton to $1500.

How's your insulation? You can get $10k in free insulation right now as well. Thats not a typo.

I'm down in Branford and I am all electric with solar. I use 2 cold climate mini splits and have had a heat pump water heater for the past 7 years. Electric bill is $9.62 every month.
 
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Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
CT has a $750 instant rebate on heat pump hot water heaters at Lowes and Home Depot. That is like 75% percent of the cost and makes it cheaper than even a standard electric tank. Just walk into any Lowes or HD and its automatically deducted.

CT is giving out money like no tomorrow for energy efficiency upgrades through its energizect efficiency program. Check out energizect.com.

The state also just tripled its mini split/heat pump rebate form $500 a ton to $1500.

How's your insulation? You can get $10k in free insulation right now as well. Thats not a typo.

I'm down in Branford and I am all electric with solar. I use 2 cold climate mini splits and have had a heat pump water heater for the past 7 years. Electric bill is $9.62 every month.
What is the size of your solar setup and what is your monthly production summer/winter?
 

EbS-P

Feeling the Heat
Jan 19, 2019
330
SE North Carolina
I gave this idea some thought ran some numbers here our power cost is 12.5c per kw hr. I needed to replace two 40 gallon short boy water heaters located in the basement. At the same time we were converting 500 sq ft garage that occupied the other half of the walk out basement to living space. I figure my heat pump is under sized by 12,000-18000 btu for the space now.
I wanted infloor radiant heat but it was too expensive. And if I could use the domestic hot water heat pump inside just would just move the heat from the inside air to the floor back to the air. See the cycle? We don’t add any extra heat to the house.
A domestic hot water heat pump that does it use outside air (say in a garage ) need ambient above about 45 F. When you heating demand is the highest you would be running only on resistive heat.
It was at this point that I realized the electric 3 space heater left in the garage when we bought the house 10 years ago and use occasionally we’re really the best answer.

so I think the real question is can a hot water heater keep your pipes from freezing while you are not home. That’s a hard question to answer with any certainty. I had my hot water baseboard heat freeze up more than once just because I set the basement thermostat to low and there was a gap in the sill plate that they ran the ptex line next to.

Heat pump hot water heater is a no brainer at this point. If it makes your space to cold in the winter switch it to all electric. After I had that installed I would really evaluate if I wanted to keep the hot water heat. I might even have it winterized and go a winter with out it. Or, more than likely I would just commit to not replacing the boiler when it reached the end of its useful like. I don’t like the idea of not having thermostatically controlled push button heat.
Last thought the problem (keeping pipes freezing while out of town in the winter ) is not really a unique problem you solution might be. Really when it comes down to the most of my answers I ask myself what is the right way solve this. If the right way is out of budget I live with till it is in budget or other more pressing items arise and it’s really not a big enough issue to address.
Right way is to remove the boiler and add heat pump(s) or replace it with a high efficiency model.
Just my thoughts. evan
 

Brian26

Minister of Fire
Sep 20, 2013
508
Branford, CT
What is the size of your solar setup and what is your monthly production summer/winter?

5.4 kw. Annual production has been around 6500-7000 kwh/yr.

Here in CT we have the 3rd most expensive electricity in the US. Hawaii is first and Alaska is second. It's been around .23-.25 cents/kwh the last few years. After the state .70/watt incentive and federal rebate the system was $9,774 or $1.81/ watt. Payback period is a little over 5 years.

Here is my monthly production numbers. The top chart is this year.

Screenshot_20201024-083616_mySolarEdge.jpg
 
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Brian26

Minister of Fire
Sep 20, 2013
508
Branford, CT
The hardware is not that complicated....its just a compressor not that different from what is on a refrigerator...and those can run for decades
My 2nd generation GE Geospring has been running nonstop in heat pump only mode for 7 years. The compressor's don't see nearly the runtime of a fridge either. Mine usually just runs for an hour to recover from a shower.

The compressor is also an Embarco that makes millions of compressors and are oem on most US brand fridges. Looks identical to the one in my GE fridge.
 

Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
5.4 kw. Annual production has been around 6500-7000 kwh/yr.

Here in CT we have the 3rd most expensive electricity in the US. Hawaii is first and Alaska is second. It's been around .23-.25 cents/kwh the last few years. After the state .70/watt incentive and federal rebate the system was $9,774 or $1.81/ watt. Payback period is a little over 5 years.
I have a 6kW system (Solaredge Inverter) that I get 11-12 mW out of annually. Last year I had 1.2mW excess power produced so I may look into replacing my natural gas water heater with the hybrid. I need to estimate how much power I will use with the hybrid to heat water.
 

Mech e

Feeling the Heat
Feb 26, 2019
330
NorCal
www.dtengineer.com
My 2nd generation GE Geospring has been running nonstop in heat pump only mode for 7 years. The compressor's don't see nearly the runtime of a fridge either. Mine usually just runs for an hour to recover from a shower.

The compressor is also an Embarco that makes millions of compressors and are oem on most US brand fridges. Looks identical to the one in my GE fridge.
Every water heater I have replaced was due to tank failure. With the hybrid, I suspect that will continue. If the heat pump fails, it will most likely be a PCA failure. It seems most OEM appliance manufacturers don't know how to design a reliable PCA.