5 gallons of oil a day Normal?

Beefboi99

I bought a 2200 sq ft. house built in 1962 with Hydronic Oil Boiler and Baseboard Radiators. I’m located in South East PA. I added a smart oil gauge to my oil tank and an Ecobee thermostat. With the weather dropping I have been using ~ 5 gallons a day of oil.

Does this seem like a lot of oil? I’m thinking my house doesn’t have great insulation and my windows are older. The thermostat is calling for heat approximately ever 15-20 minutes. But I didn’t think I’d use that much oil.

My oil tank is a single 275 gallon tank. If the smart oil gauge is somewhat accurate I’m going to be filling my tank every 30-40 days. With oil at ~$3.80/gal that’s almost like $520 a month to heat the home. 

**EDIT the boiler does my domestic water as well. During the summer I used 0.5 gal/day.**

I had a heat pump replaced this summer that does not have an electric heat kit installed yet. Would it be cheaper to add an electric heat kit and use that to heat. I rented a 2000 sq ft home before this house and the most I spent a month in electric was $350 a month with a Heatpump electric heat kit. 

**EDIT The heat pump has its own thermostat. I was using it in October for heating the home when it was 45-50 degrees outside. I noticed when the outside temp would go below 40-35 it would go into defrost mode and start blowing cold air into the home. The technician warned me that it needed a heat kit to defrost or it would blow cold air.**

Hot_water_fan

That seems about normal. Use the heat pump to save $. You can use the heat pump without the electric strips if that’s what you’re asking. Using the heat pump is 3x cheaper than using electric resistance, so don’t worry about installing the resistance. Use the heat pump and if it can't keep up (depends on the situation) you have oil ready to go.

You can try reducing your heat loss but the investment in insulation and new windows is usually a loser.

ethicalpaul

The heat strips will almost surely be more expensive than even the oil.

but yes you should definitely be using the heat pump as much as possible. Find out from the documentation or the installer of the heat pump how low the outdoor temp can be for it still to work well.

Since you have the oil for "backup" you don't even need the heat strips. They are there for supplemental/emergency heating only anyway for when the heat pump can't handle it (check me on this @Hot_water_fan to see if you agree)

My mother's heat pump is old but still heats her house just fine down to like 25F

There are thermostats that will automatically switch over from the heat pump to the oil at a certain outdoor temperature that you can set.

You have to watch out when the oil guys come to work on the furnace, though, they will switch the thermostat over to just use the oil and then "forget" to switch it back, if they are like the guys who come to my mom's house.

Also, your electric utility might give you a lower rate when you call and tell them you are using electricity to heat the house. It depends on the utility. My mom gets a lower rate due to this, they may send a guy over to verify.

Lesson: when you buy a house, ask to see the last year's utility bills. Although in this market, they might tell you to get lost and sell to the next guy.

Hot_water_fan

Another thing to consider is switching to a time of use rate if your utility offers them - get some extra low cost electricity and switch back to oil during the peak hours. 

ethicalpaul

That electricity would have to be pretty dang high to make oil cheaper than a heat pump during most eastern PA days

Jamie Hall

Cheer up, friend. Cedric has a 330 gallon tank -- and in the winter it gets filled every week. He powers a somewhat bigger house, but on a really cold day he can quite easily guzzle 30 to 40 gallons.

And to @ethicalpaul 's comment on the cost of heat pumps, there is a heat pump for an apartment in the building Cedric powers. A very good one. With our electric rates, it costs more to run than Cedric, but the tenant likes it so Cedric does the heavy lifting and the heat pump just tops it off.

Hot_water_fan

That electricity would have to be pretty dang high to make oil cheaper than a heat pump during most eastern PA days 

Fair enough! My utility in MD offers a $.36/kWh on peak, ~$.06/kWh off peak, which still almost comes out cheaper than $3.80 oil on peak. 

@Beefboi99

The calculation is: 

Oil: ($/gallon * 1000/138)/ COP =  $/MMbtu 
A COP of .85 is about the best oil will do. 

Electricity: $/kwh * 293 / COP

Electric resistance is a COP = 1, which is why you shouldn’t use it unless you have to. 

A heat pump in that climate is about COP = 3, but it changes as the temp drops. 

mattmia2

That is about 29,000 btu/hr which seems like a lot for mild to moderate weather.

mattmia2

Also try comparing the gauge to how much oil you're putting in the tank, it may not be set up right and may not be anywhere near accurate. It also may not have enough precision to measure a couple gallons of oil that accurately so you might need to look over a longer period.

bburd

One possibility is that you have a leaking pipe in one of the baseboard loops, perhaps below the slab on the lower level, and your boiler has an automatic water feeder a.k.a. pressure reducing valve or PRV. That would send a lot of expensively heated water into the ground and keep the oil burner running overtime.

You might try turning off the burner and the manual shutoff for the makeup water, then keep a very close eye on the boiler pressure gauge and see what happens. The gauge will drop a bit as the system cools down, but then it should stop dropping and hold steady.

Hot_water_fan

That is about 29,000 btu/hr which seems like a lot for mild to moderate weather.

Input, not output !

mattmia2

Hot_water_fan said:

That is about 29,000 btu/hr which seems like a lot for mild to moderate weather.

Input, not output !

25,000 btu/hr is a lot too.

EBEBRATT-Ed

@Beefboi99

Is your boiler also heating the Domestic hot water or do you have a separate hot water heater?

Your oil usage is less than 1/4 of a gallon/hour. It does not seem that excessive for 2200 sq feet.

I agree with using the heat pumps when the temp is milder to reduce oil usage and check with your installer or look up your equipment online to see what temp they can run down to. 25 degrees may be as low as you can go

STEVEusaPA

GPH (nozzle size & pump pressure) X runtime = gallons used.
You"ll have the electric company send you a Christmas present if you use back up heat strips in SE PA.
You're run time is probably spot on. Tighten up the envelope to save oil (money).

Beefboi99

Edited the OP. 

My boiler does heat my domestic hot water and during the summer the gauge typically trended 0.5 gal/day some days a little more some days a little less. 

For the heat pump, I was running it in October and it seemed to do fine when the outside temp was 45-50 degrees. When the temp outside got below 40 degrees the Heatpump goes into defrost mode and it actually starts cooling the house off. I was warned about this by the installer but I didn’t want to pay for the heat kit at the time. So I’ve been running the boiler for heat only during November. 

The thermostats are also separate from the heat pump and boiler. So the boiler does not automatically run when the Heatpump calls for emergency. Could I get away with just setting the boiler thermostat lower than the heatpump temp? 

Hot_water_fan

The thermostats are also separate from the heat pump and boiler. So the boiler does not automatically run when the Heatpump calls for emergency. Could I get away with just setting the boiler thermostat lower than the heatpump temp?

Yes or get a thermostat that goes both. You can get one that turns the boiler on during defrost. You want to shift the heating from high cost to low cost. You hear a lot about "Shoulder Seasons", the warmer, heating months. But that's too simple: even in January, you'll have plenty of warm hours. No sense paying out the nose for oil.

**EDIT The heat pump has its own thermostat. I was using it in October for heating the home when it was 45-50 degrees outside. I noticed when the outside temp would go below 40-35 it would go into defrost mode and start blowing cold air into the home. The technician warned me that it needed a heat kit to defrost or it would blow cold air.**

Heat pumps defrost - it's nothing to be worried about. If it bothers you, you can fix it. Some people have vents directed directly at their easy chair. Others will never notice a defrost. If you don't notice, just roll with it. That said, electric strips are cheap.

MaxMercy

Beefboi99 said:

With the weather dropping I have been using ~ 5 gallons a day of oil.

Does this seem like a lot of oil?

It does seem like a lot for the climate so far. In Connecticut which I believe is colder than PA, I use about 6.5 gpd in the coldest stretch of winter (Dec through Feb) on a 2800sq house using the boiler for domestic hot water, but I have 2X6 construction with R-19 insulation and double pane windows. Attic insulation is not up to snuff and I need to address that.

jesmed1

Some basic math:

5 gals/day * 140,000 BTU/gal = 700,000 BTU burned/day
Assuming 85% boiler efficiency = 595,000 BTU input into your house (the rest is lost up the chimney)
595,000 BTU/24 hrs = 24,800 BTU/hour into the house

At 40 degrees average outdoor temperature and 65 degrees indoor, that's a delta T of 25 degrees. (That's roughly what your temperature graph is showing for current conditions.)

Outdoor design temp for Philadelphia is 12 degrees, which is a delta T of 53 degrees, or roughly twice the above delta T, so when it gets down to 12 degrees, you can expect to burn about twice that amount of oil.

Then your heat loss will be roughly 2 * 24,800 BTU/hr = 49,600 BTU/hr. Divide that by your square footage and you get 49,600/2200 = 22.5 BTU/sq ft. That is actually not bad. Average new house construction is typically around 20 BTU/sq ft, and you are pretty close to that in a 60-yr-old house.

You could probably do somewhat better with better air sealing, more insulation, weatherstripping windows, etc, but to answer your question, at this point you are using a reasonable amount of oil.

jesmed1

MaxMercy said:

In Connecticut which I believe is colder than PA, I use about 6.5 gpd in the coldest stretch of winter (Dec through Feb) on a 2800sq house using the boiler for domestic hot water, but I have 2X6 construction with R-19 insulation and double pane windows. Attic insulation is not up to snuff and I need to address that.

6.5 gal * 140,000 BTU/gal = 910,000 BTU/day
Assuming 85% boiler efficiency = 773,500 BTU DOE output/day
Dividing by 24 hrs and 2800 sq ft = 11.5 BTU/sq ft heat loss.

That is darned impressive.

MaxMercy

jesmed1 said:

MaxMercy said:

In Connecticut which I believe is colder than PA, I use about 6.5 gpd in the coldest stretch of winter (Dec through Feb) on a 2800sq house using the boiler for domestic hot water, but I have 2X6 construction with R-19 insulation and double pane windows. Attic insulation is not up to snuff and I need to address that.

6.5 gal * 140,000 BTU/gal = 910,000 BTU/day
Assuming 85% boiler efficiency = 773,500 BTU DOE output/day
Dividing by 24 hrs and 2800 sq ft = 11.5 BTU/sq ft heat loss.

That is darned impressive.

Now you have me wondering. I'll check my receipts tomorrow.

jesmed1

MaxMercy said:

Now you have me wondering. I'll check my receipts tomorrow.

I didn't mean I was doubting you. I hope your house really is that good! Wish all of ours were.

MaxMercy

jesmed1 said:

MaxMercy said:

Now you have me wondering. I'll check my receipts tomorrow.

I didn't mean I was doubting you. I hope your house really is that good! Wish all of ours were.

The reason you have me doubting my numbers is that while the house is well put together, the HVAC is a two part hydro air system, and the second floor air handler is above the insulation line of the attic and not particularly well insulated.

Because I have a whole house fan that we really enjoy during low humidity weather, I didn't want to encapsulate the attic. My plan is to build a room around the majority of the air handler leaving some of the vent hoses outside the box. These I can further insulate but the majority of the heat loss will be contained in the "room" which will be about 1/5 of the attic space. Because my attic fan is near the air handler, the room will have to have a door I can open when I use the fan, and close when I use the AC, so I was looking into remote door actuators with notification.

My basement air ducts are also not insulated. Right now, I'm slowly painting the joints with a sealant and I'll insulate the ductwork by next summer.

The boiler is a Slant TR-30 with AFG and it runs well.

Anyway, when I check my receipts, I'll post back the oil use during the coldest stretch.

jesmed1

@MaxMercy If you know your average annual oil consumption off the top of your head, you can get a pretty close approximation of your heat loss without checking receipts.

We burn around 1200 gallons/yr in a 4-unit house with a total heat load of about 85,000 BTU/hr at an outdoor design temp of 0 degrees. Then 85,000 BTU/hr divided by 1200 gal/yr = 71 BTU/hr/gal/yr. This is in the Boston suburbs.

Since you and I live in roughly the same climate with roughly the same design temp and # of HDD's, you can take your annual oil consumption, multply by 71, and get your approximate heat loss in BTU/hr.

For example, if you burn 600 gal/yr,

600 gal/yr * 71 BTU/hr/gal/yr = 42,600 BTU/hr heat loss.

As I said, this only works for buildings in the same climate and neglects differences in solar gain, etc. But if you have a traditional house with an average solar gain, this method will put you in the right ballpark.

MaxMercy

jesmed1 said:

@MaxMercy If you know your average annual oil consumption

These are general numbers because I couldn't find the actual receipts. I know the dates because of emails when ordering oil which I do on line. I'm using the winter of 2021 because I (conveniently) filled in early January and my final fill was late December and it was with the new Slant boiler.

In the winter of 2021, I filled up on Jan 5. On Feb 22nd I filled again - 48 days. It took approx 240 gallons for just over 5 gallons per day in what is generally a pretty cold stretch in Connecticut.

For the year of 2021

Fill 1/5/21
Fill 2/22/21
Fill 7/12/21
Fill 12/21/21

I usually call for oil (not on reg delivery) when the tank gets to an indicated 1/8th give or take, although I don't have the exact gallons, my deliveries average from 225 to 250 at most, so I used about 800 gallons for the year of 2021 including/guessing the first 5 days of January and the last week of December. The boiler runs through the summer for DHW.

jesmed1

@MaxMercy Since your 800 gallon total included DHW, your usage for heating was maybe 600 gallons, so my example above of 600 gallons * 71 = 42,600 BTU/hr heat load may have been close to reality.

As an interesting comparison, over a similar 24-day period in Jan-Feb 2021, we burned about 10 gallons per day for a 4800 sq ft 4-unit condo building. That's about 292 BTU/day/sq ft. You burned about 5 gallons per day at roughly the same time for a 2800 sq ft building, or about 250 BTU/day/sq ft. So your heat load per sq ft is slightly lower than ours, and by taking the ratio and multiplying by our known heat load of 18 BTU/sq ft, I would predict your heat load at about 15 BTU/hr/sq ft. Multiplying by your 2800 sq ft = 43,150 BTU/hr at zero degrees. Which is quite close to the above 42,600 BTU/hr assuming 600 gallons of oil used for heating.

So your heat load of about 15 BTU/hr/sq ft is very good. That shows what you get from 2x6 construction, R-19 walls, and double-pane windows. Typical new construction is around 20 BTU/hr/sq ft.

(Note: My earlier calculation of 11.5 BTU/hr/sq ft upthread was incorrect, because that was based on a time-averaged oil consumption over a month or so in which the temperature was, on average, well above a design temp of zero degrees.)

Jamie Hall

Just for the sake of throwing numbers around, Cedric powers an historic house which, as a result, is poorly insulated (there are things you can't do to a National Historic Landmark, and installing major insulation is one of them!). He uses 0.48 gallons of #2 oil per day per degree-day, based on almost 20 years of accurate oil consumption figures. This works out to a power requirement of 23 BTUh per square foot of heated space at the -10 F design temperature of the system.

I might add that the system was designed and installed before "design" temperatures came into much use, and was intended to be able to maintain a 90 degree temperature difference between interior and exterior temperatures -- and, fortunately, can, as the actual minimum temperature he faces is between -15 and -20 depending on the year (northwestern Connecticut).

jesmed1

@Jamie Hall 23 BTU/hr/sq ft is actually quite respectable for an old building if you believe this article, which gives ballpark ranges for "typical" houses of various age ranges. His worst-case "Type C" houses of 40+ yrs have heating loads of 40-50 BTU/hr/sq ft. That makes Cedric's house look quite good by comparison.

https://inspectusa.com/blog/typical-heating-cooling-loads-in-older-homes/

I appreciate hearing numbers from you and @MaxMercy, because I've been trying to gauge how bad/good our 100-yr-old condo building is relative to others in the MA-CT area. At 18 BTU/hr/sq ft, we're somewhere between Max at 15 BTU/hr/sq ft and you at 23 BTU/hr/sq ft. Though I do note that your design temp of -10 is lower than mine (zero), so on apples-to-apples, we're not that far apart.

MaxMercy

Thanks for the calculations.

I know I can do better. The first step is getting a dedicated water heater to use during the summer.

The second is to getting my attic air handler inside an insulated envelope (which will also help my summer A/C), and third is to insulate my basement duct work.

I think I can knock off 200 gallons from my yearly usage between the water heater and the insulation issues I have left to address.