The house I live in has an existing oil-based boiler for both heat and hot water. The hot water tank (50 gallons) will likely need to be replaced in the next few years as it is more than 10 years old, probably approaching 15. I am on well water without a water softener, and I assume that the previous owners never did any sort of maintenance with the current hot water tank. (A neighbor mentioned that there is some sacrificial part that can be replaced every so often to extend the life of the tank.)
I keep reading that the hybrid heat pump water heaters are incredibly efficient, and I hate having to burn oil during the warmer months just to heat my showers. My plumber tells me that it’s a really efficient system and that I should keep it intact as long as I can. He also seems a bit old school in his opinion and preferences, as he scoffs at the idea that I would eventually like to replace the whole boiler and system with a heat pump system instead.
Is there a good place to learn about how my existing system works, and any way to compare to possible savings (or pitfalls) of switching to a new system? Are there other options, such as tankless hot water heaters, that I should consider? I gather that recovery time with a hybrid heat pump water heater will be much slower than the existing system, so should I also calculate for a larger system (65 or 80 gallons)? Two adults live here full time but we frequently host guests and family gatherings, and we sometimes need enough hot water for 10 or so adults to shower. There are three full bathrooms in the house and one day we may add a fourth.
(A neighbor mentioned that there is some sacrificial part that can be replaced every so often to extend the life of the tank.)
It’s called a sacrificial annode. It’s purpose is to attract all the rust to it’self to prolong the life of the tank. They’re supposed to be replaced every 3years or so, even more frequently if you’ve hard watter.
Most people don’t know and have never checked. If it’s been more than 5 years, it’s probably just a thin red mud at the bottom of the tank. (one of the reasons water is drawn from the top).
I replaced my gas water heater with a heat pump water heater. It’s great! I live in a humid climate and having the extra cooling/dehumidifying in the summer is a great bonus. It does make the basement noticably colder all year round though. The energy/financial savings are essentially, I get free hot water in the summer, and a little extra demand for heating the house in the winter.
Recovery time is not really noticeable unless we have company staying with us. My Rheem unit has a “High Demand” mode that kicks on both the heat pump and resistive elements to provide recovery comparable to a gas heater.
The old heater was end of life and the local incentives made it cheaper to install a heat pump water heater than any other type. 15-20 years is considered end of life, most warranties only go to 10 years.
Most tank water heaters have a sacrificial rod or two regardless of heat source
Tankless water heaters are really only practical with burning either oil or gas, the main benefit being you’ll never run out of hot water.
Undecided with Matt Ferrell has a good video on heat pump water heaters Technology Connections has a good video on home electrification
Edit: find a contractor(s) who know how to work with local incentives. Federal tax credits were ended by the “Big Beautiful Bill” last year.
unit has a “High Demand” mode that kicks on both the heat pump and resistive elements to provide recovery comparable to a gas heater.
This is the thing that people often ignore about heat pumps. Resistive heating elements, while only 100% efficient, are super simple. If you end up having to run the resistive elements a few times a year, it’s no big deal, it’s not going to break the bank compared to having a much larger system.
If you don’t live in a hot climate, many heat pump water heaters take heat from indoor air. Be aware of that - you’re heating air, then moving that heat into the water tank. It really drops efficiency. But they’re almost certainly a lot cheaper to run long term than paying for oil deliveries! They’re not necessarily cheaper than gas, because gas is just so cheap. I’d be wary of replacing a working system, because it’s probably not going to break even, but check for incentives that might help with the cost.
If you make the investment, a water softener could be a good investment. Draining/flushing and maintaining the anode rod is a big factor in longevity.
Tankless is ok, but it burns oil or you need pretty serious electric service. One downside is that the hot water piping doesn’t get the heat transfer from the tank of hot water so the whole pipe length cools fairly rapidly; 1hr between showers and you need to run the tap for a while.
I believe that a heat pump boiler should have backup electric heating elements that kick in when there’s high demand or if it is too cold for the heat pump to keep up.
it really drops efficiency
Eh, not in comparison. Burning oil counteracts your AC, so both fight your HVAC somehow. And heat pumps are more than 100% efficient. I.e they can heat the water more than the amount of energy spent.
heat pumps are more than 100% efficient.
This is true if you are pulling the heat from outside of the house. If it pulls from inside, and you are needing to heat your home, it can only be %100 efficient since it’s a closed system. Depending on where you live, though, the extra cooling is more of a positive than a negative, though.
I wonder if anyone makes a heat pump water heater that can pull from both outside or inside.
I almost built that for my last house but ended up moving before I could. It wouldn’t need much, just an extra pipe with a baffle and a door that opens internally.
You need to be licensed to work with refrigerant, though, right?
No refrigerant. Just a stream of cold air coming from a vent on the unit.
Well, there’s probably a refrigerant in there somewhere. But it’s not like HVAC system with a refrigerant line and a compressor outside. It’s all contained within the unit, and cold air just pours out. You can direct that using ducts.
Ah, so that’s like the 50% solution. You can choose to exhaust cold air outside, but still pull warm air from inside either way.
If there were two refrigerant loops, you could choose between pulling heat from outside/exhausting “cold” outside, and pulling heat from inside/exhausting “cold” inside.
I dont have it in me to try to calculate what efficiency gains you’d get for that trouble, though.
Tankless systems require frequent descale maintenance to maintain the warranty.
Yes but make sure you get a really solid labor warranty. We got a State branded hybrid water heater and the heat pump failed in the first year. Had it failed after one year we’d be on the hook to pay foe the labor to replace it even if the water heater itself was covered under warranty.
Thankfully the replacement has been flawless so far, hopefully it was just a fluke.
It’s so neat walking into the utility room and feeling the air is noticeably cooler and dryer, especially with my modest almost-homelab setup in the same room. I love being able to feel that its doing its thing, and that’s also how I knew the previous one had its heat pump fail, it was immediately obvious when walking into the room after no hot water.
Even when the last one failed, it was one button press to make it fall back to the resistive heating (I run mine in pure heat pump mode full time) and that worked perfectly fine until the replacement installation
Pitfalls:
You have a small space: heatpumps need airspace and it needs to circulate. An enclosed closet won’t work.
Your heater is outside: heatpumps pull air through and dust/cobweb buildup isn’t good.
You dont have electricity to the heater: heatpumps need a decent cuirruit size to run. Some can run off a small 120v circuit.
You didn’t size right: heatpumps can’t keep up with sustained demand usage. A larger tank offsets this.
You can keep your old system too though. Just put your hybrid before it and set your temps at like 125 for the heat pump and 120 for the boiler. Your boiler will rarely need to run unless you have sustained usage, a power failure, or it needs to bring temps up in the water it’s holding.
Heatpumps can have an external element to exchange heat.
I haven’t seen a water heater with one though.
The eternal plate can get frost on it in the middle of summer.
Here’s a This Old House video explaining the system and why it is better for colder climates.
We swapped last year. Getting hit with several big oil bills every winter sucked, and the price doesn’t really go down.
Oil furnace hot water baseboard heat - yearly boiler cleaning and maintenance, oil filter changing, complex issues like valves, pumps or whatever that we’d had that probably averaged easily a couple hundred a year in preventative and actual maintenance. Roar under the floor when the unit kicked on. Negotiating delivery schedules and price contracts with heating oil services. Colder than normal and need an earlier delivery? Fee. Takes a while to warm the house up due to needing to heat the mass of water and circulate. Got rid of a big boiler, pipes, and fuel tank.
That said, I found the baseboard heat very comfortable and uniform during winters. I miss that slow, even heat sometimes.
Heat pump system - removed our built in AC handler and installed the heat pump unit, forced air, used existing ducting from AC. Got several thousand in incentive rebates from the State to install the efficient units. Covered installation costs easily. Maintenance is far easier, I swap a HEPA filter every 4 months or so myself. Quiet operation, quicker heating or cooling. Love the dehumidifying feature during summer, it gets really humid.
Downsides: drier air in the winter, we now run a regular ultrasonic humidifier in the winter, but could have installed a whole-house humidifier with the unit. That would have cost thousands more. The unit is the “extra” efficient version that is supposed to run down to -20. Wouldn’t you know it, this was the coldest winter for the longest stretch we’ve had in forever, and the unit struggled. We did not install the “heat strips” that would have added more heat in such a situation. Again, thousands $ more.
And of course the electric bill is higher. I would say that the additional electric cost compared to the overall oil cost, maintenance, and contracts for the oil furnace is lower. Not ridiculously lower, but the heat pump system is clearly a winner as far as cost to operate.
Summing up…Get a good heat pump for your climate. You will realize savings and a reduced headache for maintenance. However, it isn’t a miracle solution.
I’m going to assume a solar heater isn’t n option where you live. I’ve got that on the roof works great where I live, basically no energy cost once you install AFAIK (I rent)
What is your goal? To save money? How much more does a heat pump cost? How quickly will the energy savings add up to the difference? How much more expensive and frequent will maintenance be?
If you live in the US, power company and tax rebates make it much more attractive to get a heat pump water heater.
If you live in a warm climate, you can add a duct to the water heater exhaust to move the cold air somewhere warm, like a garage or an attic.
https://www.bchydro.com/powersmart/residential/tips-technologies/heat-pumps.html
Your local energy provider might have info on that.
You may not need to plan for a larger capacity. Many of the new heat pump water heaters over heat the water, then mix it back with a little cold before sending it to the taps at your desired temp. You get something near 75 gal out of a size 50 tank.
Heat pumps don’t work in freezing temps so replacing your entire system with a heat pump is a bad idea. Heat pumps are very efficient, so adding a heat pump to support your current system is a good idea.
And your plumer is right about it being efficient, at least as far as hot water for showers etc. during cold months. I’m not so sure how efficient that is during hotter months so using a heat pump for hot water during hot months would be efficient though.
Geothermal Heating is the most efficient but also the most expensive(15k-30k ish).
Yet somehow Scandinavia manages just fine with their heat pumps
These days, they make heat pumps that work in freezing conditions. Plus, a lot of the heat pump water heaters have the heat pump directly on top of the unit, so if your water heater is in conditioned or semiconditioned part of your house, it shouldn’t ever reach temperatures where it runs into inefficiencies.
Heat pumps are some of the only appliances that have more than 100% efficiency. They’re practically magic, and I think everyone that can afford them should get them. Of course, for house heating, you should still have a backup furnace (my heat pump has an electric backup)
I guess my info was outdated, thanks for the correction.
Unfortunately they use a stupid amount of electricity and cost a lot to run. Source: installed 2 Mitsubishi heat pumps last year in northern Maine. Electricity delivery rates are insanely high here.
Sure, YMMV. But I replaced an oil fired furnace with one. Back in 2021, I had to spend about $900-1000 every three or so months in the winter. My heat pump comes out to about ~$60 a month, or $180 for the same timeframe at the same time of year. My area has relatively cheap hydro @ ~$0.15/kWh (USD) and it was a no-brainer. Even if my electric was $0.60/kWh, it would still have been cheaper in the long run. Note that I only have one of course, so it’s different than your setup, but mine is also a Mitsubishi.
I can’t imagine what it would cost to fill my oil fired furnace tank these days. After doing some research, it seems that heating oil prices in my area are around $5.90(!), meaning to fill my 500 gallon tank, it would be nearly $3,000. Of course, I never ran it empty, but it would still have been around $2k these days… for three or so months. That’s insanity. The heat pump has already paid for itself multiple times over by this point.
It’s important to note that while they sure do use a lot of electricity, they’re extremely efficient. In most cases, they can double (or triple) the amount of heat energy output than energy consumed. Resistive electric heating can’t do that, neither can natural gas, oil, or any other form of whole home heating (except maybe if you’re lucky enough to have geothermal heating, but it could be argued that geothermal is also a form of heat pump).
For the record, my heat pump system works just fine throughout the entire year, including the times in the depths of winter where it drops into the single digits or, in the case of this last winter, below zero on the Fahrenheit scale. (That’d be -17° C, for our Euro bros.) And no, mine does not have resistive electric backup heat.
Heat pumps work just fine to about -10° and cold climate air to air heat pumps go comfortably to -30, and most maintain >100% efficiency to about -20.
Unless you live somewhere that drops to absolute zero this is bullshit.
