Trying to figure out total savings of switching from oil to LP

tommygags

Hi everyone. Trying to help my parents determine if they should make the switch from their 35 year old oil boiler to a tankless LP high efficiency boiler. Their oil tank is also 35 years old and although they don't have any problems, they want to replace the underground oil tank Incase it starts to leak, which started this whole discussion.  Or if they should just replace the oil tank and keep everything as is. 

Besides the cheaper price per gallon (about 10% cheaper), are there some estimates or online calculators that can help estimate yearly savings using a high efficiency condensing boiler vs a 35 year old oil boiler?

They live in the north east
4k sqft home
Heating is radiators
DHW is a 50 gallon tank
3 ppl in home


Thanks!

kcopp

https://www.amsenergy.com/fuel-cost-calculator/

I can see wanting the tank out of the ground.
A new tank inside is prob your bet best.
If the boiler is in good shape keep it.
The high efficiency they promote will only be if you are running lower water temps. If the system runs at 190F all the time there will be no savings.

EdTheHeaterMan

When you say "Radiators" are you talking about Cast Iron radiators look like this?OR
Panel radiators the look like this?OR
Baseboard radiators that look like this?

There is a reason because the last one, the baseboard radiators, will yield the least efficient use of a Modulating Condensing (ModCon) boiler because the return temperature from those radiators will be to high to realize the savings of the Condensing boiler. The first one, the cast iron radiators, are probably older than the 35 year old oil heater you have. If they were installed in the 1920s or 1930s, there is a chance that they can operate at lower temperatures that will get more efficiency from the Condensing boiler.

So which radiators do you have?

depending on the combustion efficiency of your 35 year old Oil Fired boiler, and the type of radiators you are connecting to, there may be a savings by switching to LP Gas. Not because the fuel cost per unit of power is better. because the fact that you can get over 95% fuel efficiency from a gas boiler where you may only get 80% (+,-) efficiency from your oil boiler.

So the more efficient boiler connected to cast iron radiators can actually use a more expensive LP gas with greater efficiency than the oil fired boiler using the lower price fuel oil. You see LP Gas contains about 91,333 BTU per gallon while Fuel oil contains 140,000 BTU per gallon. So when you compare the price per gallon of oil to the price per gallon of LP Gas there are several factors to consider.

1. How efficient the appliance will use the fuel
2. The price per gallon
3. The BTU per gallon
4. Cost of maintenance on the equipment
5. What a leaking fuel oil tank might cost
6. How long you plan on living there.

bburd

Keep in mind that while a gallon of No. 2 heating oil has a heating value of 138,000 BTU, a gallon of propane has only about 90,000 BTU. You have to buy many more gallons of propane to get the same amount of heat.

The comment above about high-efficiency boilers and supply water temperature is well taken. If you have baseboard radiators or fin tube convectors, the high-efficiency boiler is not much of an advantage because these systems require high water temperatures and most of the time it will not be able to condense. If you have radiant floors or an older system of cast-iron radiators, the high-efficiency boiler is more of an advantage. They do need annual servicing and most only last 10 to 15 years, so while conventional boilers use a bit more fuel the lifecycle cost is frequently less.

if you stay with oil, a basement tank is a much better idea than an underground tank from a leakage standpoint.

Steamhead

What make and model is their present boiler?

tommygags

Thank you everyone for the in depth responses! 

They have baseboard radiators and he keeps the water temp to 180.

Based on everything you all just said, it doesn't look like it would make sense to switch over to LP. 

I will find out the make and model of his boiler tomorrow. 

Maybe looking into heat pumps is the better option?

Jamie Hall

No, heat pumps aren't a better option -- you'd essentially be scrapping the present system entirely, No air to water or even, so far as i know, ground source heat pumps can get the water temperature high enough to make those baseboards run.

Further, "northeast" is a pretty elastic term. If you are south of New York City, or along the coast as far up as Boston, you might be able to actually heat the house enough with heat pumps. Otherwise... not yet, anyway.

EdTheHeaterMan

I had a boiler in my home for the 30+ years that I raised my family in southern NJ. I was very comfortable at 68° in that home even on the coldest days. I now have in a single home in Charleston, South Carolina with a 34 year old heat pump. I am freezing in the winter with the temperature set at 73°. The heat from radiators (at 180°) is superior to the cold air (100°) being blown around by my heat pump. And the weather is warmer in SC!

hot_rod

How are you generating hot water? A coil in the boiler.? Cooking and drying clothes, electric? Barbecue? All those could be LP also.

The tough number to come up with is the actual efficiency of the current boiler. Short cycling boilers from commonly oversized cast boilers can drive the efficiencies into the 50% range.

What size is the boiler and how many feet of baseboard is connected to it? That is a good place to start to match up what you have with what you are considering.

Another good number to know is the heat loss of the home and how it matches up to the fin tube output.

Oil and LP can vary a lot in price based on many conditions outside our control.

If it is possible to run a consensing boiler in the high efficiency mode for part of the season, that too changes the math. You could run 90% efficiencies for some of the year. Even in high temperature operation count on a condenser giving you 85% efficiencies. Most new boilers have outdoor reset control onboard, more savings and comfort options.

So the math is not so straight forward.

Here is a simplified calculator that you can put some actual numbers into and get an answer.


https://coalpail.com/fuel-comparison-calculator-home-heating

Toggle between oil and LP here.
https://www.eia.gov/dnav/pet/pet_pri_wfr_a_EPD2F_PRS_dpgal_w.htm

Hot_water_fan

You can condense with baseboards with no issues - you only need the highest temps at the coldest outdoor temperatures. There’s no reason to think that you need 180 degrees currently either - that’s usually just the default. 

If the parents want AC, then heat pumps are the way to go. You can still keep the boiler if desired. 

Jamie Hall

Realistically, @tommygags , we don't have enough information to suggest a change to a completely different heating system. The question of money savings -- if any -- for changing from an older oil fired boiler to a newer gas fired boiler is actually not that difficult, although even there there are variables which we don't have which will affect how much money, if any, you would save.

One of the key questions in that calculation -- never mind trying something like a heat pump -- is the relationship between your installed radiation capacity and the heat loss of your house -- not just at design temperatures, but at intermediate temperatures. Nor do we have enough climate information to determine what the relative time your system operates under mild temperatures vs. more extreme temperatures, when the full power of you existing system is needed.

Answering some of @hot_rod 's questions will help you a good deal along those lines.

If you can find a true heating professional in your area -- one who has good expertise in all types of heating and cooling systems -- to come and evaluate your application for the best option among the many would be helpful. Unfortunately, it is hard to find one of those. Try to avoid a salesman or a one note Charlie; they are much easier to find, and will cheerfully sell you what they have or what they believe in, not what you need or want.

hot_rod

Another important step would be to tighten up and insulate the home as best as possible. In some areas your utility will do an energy audit and suggest ways to lower fuel consumption. They may even cover the cost of some upgrades.

www.dsireusa.org will show any programs in your area

Then do the heat load, baseboard survey, and boiler size and temperature requirements.

This journal has some ideas for lowering supply temperature even with the system you have.

https://idronics.caleffi.com/magazine/25-lowering-water-temperature-existing-hydronic-systems


Notice in this data for upstate NY.
Suppose the coldest day, 0 degrees, requires 180F. Any day above 0° the supply temperature from the boiler could be reduced. So on a 30° day you may only need 150°.
Lower boiler temperatures = lower energy consumption and cost.

Another slide shows the 3-1 ratio for fuel savings.

AND around a 68° day the heating would be free

So do some more number crunching to get a good answer to your question.

pecmsg

With the cost of the equipment and the labor to install it I doubt you’ll ever see a return on investment

EdTheHeaterMan

Agree with @pecmsg. For someone to replace a perfectly good, working heating system, that has a life expentaccy of at least 10 more years, there will rarely be a savings or even a break even point.

On the other hand, if the heating system is going to be replaced regardless of type, then there are savings and break even points based on certain choices.

Step 1 Is to look at the least expensive choice of the replacement options. WE will call that X
Step 2 Is to look at the cost of operation and maintenance over the next 10 years for X
Step 3 Is to look at the additional cost of the upgrade. We will call that (Y-X)
Step 4 Is to look at the lower cost over the next 10 years for equipment Y
Now compare the total or the cost in step 4 plus (Y-X) with the cost of step 2 and see if there is a savings

Basically if spending $1000.00 more for a better heater today will save $2000.00 in operating and maintenance costs over the next 10 years then select the more expensive equipment. Unless you have a guaranteed compound interest rate of 8% or higher, the $1000.00 is better spent on the better equipment.

Higher cost energy costs will actually improve your savings over 10 years all things being equal, which energy costs usually rise equally over the long run.

hot_rod

Any idea on how long they may be living in the home?
Resale would be much better with heat and air, especially watching current weather related events.

Their quality of life my be better in a conditioned home, temperature, air quality, adding or removing humidity, etc. So it is not always just a $$ decision.

tommygags

Thank you everyone for all the great advice! I still need to look at everyone's comments but wanted to share some more information 

House was built in 1989, open floor plan, high cathedral ceilings in some areas, 4k sqft
They are located in CT. 
Boiler is 248k BTU
Ft of baseboard, roughly 200ft; this is in addition from piping going from the boiler in the basement to first and second floor of home.
They also have their kitchen, which is radiant heat, about 600 ft of tubing. 

hot_rod

tommygags said:

Thank you everyone for all the great advice! I still need to look at everyone's comments but wanted to share some more information 

House was built in 1989, open floor plan, high cathedral ceilings in some areas, 4k sqft
They are located in CT. 
Boiler is 248k BTU
Ft of baseboard, roughly 200ft; this is in addition from piping going from the boiler in the basement to first and second floor of home.
They also have their kitchen, which is radiant heat, about 600 ft of tubing. 

Yikes! If you can determine the brand and model of the baseboard you could come up with actual output.

Assume 550 btu/ ft of common residential fin tube X 200' = 110,000 btu/ hr output.
Does the home maintain temperature on the coldest days? if so the amount of fin tube is probably adequate, maybe oversized.

So add maybe another 15,000 for the radiant floor. So a boiler with an output of around 125,000 btu/hr would seem about right. So that boiler could be twice the size that is needed.

The heat load number could help dial in the numbers.

There are some formulas that could determine actual cycle efficiency by timing the burner on vs burner off cycle times. I think it is safe to say the current boiler is quite a bit oversized, running low efficiencies.

tommygags

hot_rod said:

Thank you everyone for all the great advice! I still need to look at everyone's comments but wanted to share some more information 

House was built in 1989, open floor plan, high cathedral ceilings in some areas, 4k sqft
They are located in CT. 
Boiler is 248k BTU
Ft of baseboard, roughly 200ft; this is in addition from piping going from the boiler in the basement to first and second floor of home.
They also have their kitchen, which is radiant heat, about 600 ft of tubing. 

Yikes! If you can determine the brand and model of the baseboard you could come up with actual output. Assume 550 btu/ ft of common residential fin tube X 200' = 110,000 btu/ hr output. Does the home maintain temperature on the coldest days? if so the amount of fin tube is probably adequate, maybe oversized. So add maybe another 15,000 for the radiant floor. So a boiler with an output of around 125,000 btu/hr would seem about right. So that boiler could be twice the size that is needed. The heat load number could help dial in the numbers. There are some formulas that could determine actual cycle efficiency by timing the burner on vs burner off cycle times. I think it is safe to say the current boiler is quite a bit oversized, running low efficiencies.

Thank you Bob for this useful information!  Is it safe to say a boiler twice the size it should be, uses about double the amount of oil than a properly sized boiler if that is half the size?

Yes, the house maintains temperature on the coldest days. 

Slant Fin is the brand, from 35 years ago. 

tommygags

hot_rod said:

How are you generating hot water? A coil in the boiler.? Cooking and drying clothes, electric? Barbecue? All those could be LP also. The tough number to come up with is the actual efficiency of the current boiler. Short cycling boilers from commonly oversized cast boilers can drive the efficiencies into the 50% range. What size is the boiler and how many feet of baseboard is connected to it? That is a good place to start to match up what you have with what you are considering. Another good number to know is the heat loss of the home and how it matches up to the fin tube output. Oil and LP can vary a lot in price based on many conditions outside our control. If it is possible to run a consensing boiler in the high efficiency mode for part of the season, that too changes the math. You could run 90% efficiencies for some of the year. Even in high temperature operation count on a condenser giving you 85% efficiencies. Most new boilers have outdoor reset control onboard, more savings and comfort options. So the math is not so straight forward. Here is a simplified calculator that you can put some actual numbers into and get an answer. https://coalpail.com/fuel-comparison-calculator-home-heating Toggle between oil and LP here. https://www.eia.gov/dnav/pet/pet_pri_wfr_a_EPD2F_PRS_dpgal_w.htm

Thank you. 

Based on that calculator, and current rates. An oil boiler at 50% vs a propane boiler at 85%, would save him about $1,500 per heating season (150millon BTUs). 

If they can get away with lowering their water temp to 160 (down from 180), would that get a propane boiler to 85% efficiency, or still too high of a temp?

Hot_water_fan

Thank you Bob for this useful information! Is it safe to say a boiler twice the size it should be, uses about double the amount of oil than a properly sized boiler if that is half the size?

Probably not double, but it's more than necessary. A modern boiler can be oversized a bit better due to what we've learned (basically a pump is left running to remove some of the heat post heating call), but why oversize if you can avoid it.

Jamie Hall

"Is it safe to say a boiler twice the size it should be, uses about double the amount of oil than a properly sized boiler if that is half the size?"

No. It will use more, as cycling on and off is not as efficient as constant running, but nowhere near twice as much. 10 percent would be more accurate as an upper limit on the additional amount, and it depends very much on the exact nature of the cycling which the boiler will have.

This will apply to whatever fuel is being used -- it is not unique to oil.

That said, it should be also observed that a poorly maintained oil boiler does lose efficiency to a somewhat greater extent than a poorly maintained gas fired boiler. The very low overall efficiencies sometimes cited for oil boilers which are too large are almost always more closely related to inadequate maintenance than to being oversized.

Now you also ask if being able to reduce the circulating water temperature to 160 F will allow a gas fired boiler which is intended to condense (not all are) will yield improved efficiency. Not much, if any, is the answer. You need to get down to the dewpoint of the exhaust, which is around 140, for the improvement to take place. Both a properly maintained oil fired boiler or gas fired boiler should operate in the 80 to 85 percent range at that temperature. I'll say it again: if the oil fired boiler is operating at 50 percent, it has been improperly maintained and adjusted -- or possibly, is just very old (like 40 to 50 years old). I might add, in some defence of the technician working on the boiler, that it is necessary that he or she be well acquainted with the use of appropriate instruments to properly adjust the boiler, and that he or she take the time to clean it completely.

tommygags

Jamie Hall said:

"Is it safe to say a boiler twice the size it should be, uses about double the amount of oil than a properly sized boiler if that is half the size?" No. It will use more, as cycling on and off is not as efficient as constant running, but nowhere near twice as much. 10 percent would be more accurate as an upper limit on the additional amount, and it depends very much on the exact nature of the cycling which the boiler will have. This will apply to whatever fuel is being used -- it is not unique to oil. That said, it should be also observed that a poorly maintained oil boiler does lose efficiency to a somewhat greater extent than a poorly maintained gas fired boiler. The very low overall efficiencies sometimes cited for oil boilers which are too large are almost always more closely related to inadequate maintenance than to being oversized. Now you also ask if being able to reduce the circulating water temperature to 160 F will allow a gas fired boiler which is intended to condense (not all are) will yield improved efficiency. Not much, if any, is the answer. You need to get down to the dewpoint of the exhaust, which is around 140, for the improvement to take place. Both a properly maintained oil fired boiler or gas fired boiler should operate in the 80 to 85 percent range at that temperature. I'll say it again: if the oil fired boiler is operating at 50 percent, it has been improperly maintained and adjusted -- or possibly, is just very old (like 40 to 50 years old). I might add, in some defence of the technician working on the boiler, that it is necessary that he or she be well acquainted with the use of appropriate instruments to properly adjust the boiler, and that he or she take the time to clean it completely.

Got it, that makes sense. Thank you Jamie for the additional information and indepth response!


Anyway to tell or estimate what the current efficiency is? 

hot_rod

The word efficiency can be used in a number of different ways in heating systems.

Most simply desired output÷necessary input.

Steady State Efficiency when all is going well everything constant air to fuel ratio, air temperature, return water temperature, a clean well dialed in burner basically.

Steady State heat output ÷ energy input

Combustion Efficiency, a combustion analyzer would give you these numbers. The temperature and Co2 content of the exhaust under steady state operating condition.

Cycle Efficiency, here is where you may be taking a big hit, heat output over a period of time ÷energy content of fuel consumed over that time period.

The Run Fraction can lead you to cycle efficiency heating requirement ÷ steady state heat output

With that number use this graph to get an idea of cycle efficiency.

So for example a home with a heat load of 100,000 btu/hr, at 0F outdoor, maintaining 70F indoor on this day. The home has a boiler with a 150,000 btu/hr heat capacity (obviously oversized)

That home at a 40F outdoor condition would look like this

100,000 (70-40) ÷ (70-0) deduct some internal gains from appliances, people, cooking etc 20K leaves you with 22,860

Run Fraction is 22,860 ÷ 150,000 = 15%
Plot that into this graph and your alleged 85% boiler is running 72% at these conditions.

Using past weather data you could determine how often you at at various outdoor conditions and plug a range of numbers into this formula. I predict rarely if ever are you running at 85%, based on the info we know so far.

What you get with a mod con style boiler in your case is MODULATION. A properly sized boiler with a 10-1 turndown would run at the steady state condition for most, maybe all of the heating season.
The modulation combined with outdoor reset control could possibly keep that boiler running non stop providing the exact amount of heat input as the building needs under varying conditions. That would be the holy grail of boiler operating condition. So even running a mod con at higher temperature 180 and below based on outdoor, you will still be in the mid to high 80% range.

When the load is satisfied you get 100% efficiency. The boiler is off

The biggest question, impossible for any of us to determine does it make sense $$ to change or upgrade. Only you can make that decision. And that too will be based on unknowns like fuel costs, how long you or the folks will be there, maintenance costs of the old vs the new equipment, rebates available for upgrading to high efficiency equipment, etc.

Hopefully this helps shed some light on a difficult decision.

Steamhead

tommygags said:

.....Boiler is 248k BTU......

What make and model? Some boilers can be fired at different rates................

rsilvers

Every time I have done the calculation, oil ends up cheaper. Propane can run stove and generator, so there is that benefit. 

You need to use a website where you plug in the cost per gallon of each and the efficiency of each burner and it will tell you. 

Check heat pump rebates. $10,000 in MA. 

Jamie Hall

Wow! Free money (courtesy of your taxes, of course). Question: is that rebate accessible if you want to keep you existing system for those days when the heat pump can't hack it?

hot_rod

Lp prices vary quite a bit across the nation. LP is the predominate fuel in the rural midwest

End of last week around 2 bucks a gallon in Kansas, 3.80 in CT