Fuel Oil Usage.

ConnecticutYankee · February 7

Guys,

I'd like to estimate the increase in fuel usage if I raise the temperature inside my house from the current setting of 66 degrees to a more comfortable 68 degrees. I burn 900 gallons annually with roughly 700 gallons for radiant heating.

What would you guys suggest or recommend for a method of calculation? An estimation of any accuracy would be helpful.

It's likely that keeping my existing Weil-McLain Gold oil-boiler makes more financial sense than upgrading to any other equipment and/or conversion to propane. The ROI just doesn't seem to be there. For example, if I'm spending $3k per year now (possibly $5k per year at 68-70 degree thermostat setting), the savings yielded from installing the Viessmann Vitocrossal would be marginal at best. Certainly not enough to justify spending the equivalent of a new Harley Davidson Street Bob.

I appreciate any feedback. All the best to you guys!

Here's my even longer-winded post from last week with more detailed information.

Which Viessmann boiler to buy?

ConnecticutYankee

Jan 30, 2025

Hi guys,
This will be my first post. I've been reading this forum for decades and appreciate the knowledge I've gained from all of you over the years. I’m hoping that you can help me make a decision in regard to which new boiler I should buy.
We bought a brick ranch four years ago here in Connecticut that was built in 1952. The main part of the house is 1752 square feet and is heated by cast-iron radiators. The house also has a two-story wood addition that’s an additional832 square feet and is heated by a hydro-air unit (too small @ only 31,200 btu’s)which is on its own zone. The current three-zone system has a twenty-year-old Weil-McLain Gold series pin-style oil-fired boiler that's rated @ 126,000btu's. A few months after moving in, I had a Viessmann Vitocell 300V 53-gallonindirect water tank installed - which replaced a very old indirect which was long overdue for replacement.
Unfortunately, I recently discovered a leak underneath the 275-gallon oil tank. It wasn’t much, maybe three or four ounces. The oil tank is almost 25 years old. It doesn’t seem to be happening when oil is delivered but slowly drips every few days. This might not seem like something to worry about, but the potential for a catastrophic tank failure is nothing to ignore. The replacement of the oil tank also factors into my buying decision. A new double-bottom tank from Granby will cost around $4,000.00 installed. This is why I am leaning towards a gas-fired boiler.
Fuel oil consumption is modest. We burned 900 gallons total in2024 with the thermostat set at a constant 66 degrees without any time-of-day setbacks. If you subtract the oil used for making hot water (plus the boilers internal water), the fuel used for heating is probably around 700 gallons a year. That’s both good and bad. The good is that I spend just about $ 3200.00 per year to heat my whole house at current oil prices. The bad is that the potential for saving money by replacing my old system will be minimal (let’s assume under a thousand dollars per year). The good is that as we age (currently fifty years old) we will have to raise the temperature to feel comfortable (the elderly set the thermostat as high as 75) and not suffer the increased fuel usage from our old boiler. The potential for fuel savings might be substantial if the house was indeed heated to 75 degrees (let’s assume the savings to then be several thousand dollars annually). We’d be happy with 68 degrees for the foreseeable future. We might convert the existing attached two-car garage into an in-law apartment in a few years (it’s currently unheated but would be nice to have a Modine Hot Dawg hydronic ceiling-mounted 20k btu garage heater in the meantime) which has to be factored in when sizing the boiler.
Here are the three boilers that I’m considering:
Viessmann Vitola (oldie but maybe the best oil-fired boiler ever made / new NOS units still available on the secondary market).
Viessmann Vitorond 100 (probably the best oil-fired boiler “currently” available).
Viessmann Vitocrossal 300 CU3A (Gas condensing boiler but floor mounted and has 5 stages of modulation with a high-mass water content of 13 gallons).
They have been chosen based on several criteria - but primarily durability first and energy efficiency second. For example, the Vitola could last forty years or more if properly maintained and you store a good inventory of spare parts yourself. The Vitola is also very cheap, I could buy them for $ 1500.00 a piece right now. The Vitola and Vitorond would be hooked up to a new oil tank and the Vitocrossal would burn Propane. We have a small 125-gallon propane tank next to the house currently but I would need to have a large 1000-gallon propane tank buried in the side yard if I wanted to be able to purchase propane smart when the price is lower during off-peak times. Installing an in-ground propane tank would be expensive but possibly worth it for increased curb-appeal.
I’m also a little concerned that Carrier bought Viessmann. This could eventually have negative consequences for those of us that love Viessmann products. It’s worth considering a purchase now before the brains at Carrier decide to discontinue either the Vitorond or Vitocrossal.
What are the potential benefits and/or drawbacks to thesethree boilers in your opinion(s)?
I’m looking forward to reading the replies - both good and bad. This ended up being a long write-up, my apologies!
Thank you!
Mark

pecmsg · February 7

Tightening the envelop will give a much higher return on investment than any high efficiency equipment.

Get a blower door test done, find and fix the leaks. Storm windows, even the 3M plastic film helps. Insulation.

Hot_water_fan · February 7

Increase will be minor.

Using Hartford's heating degree days:

Last 12 months, base temp 61F: 4486

Last 12 months, base temp 63F: 4964

So about 10% more usage.

techforlife · February 9

You might burn 50 to 100 gals. more, that's all. If you want to replace the boiler, EK System 2000 uses the least fuel.

pecmsg · February 9

https://forum.heatinghelp.com/discussion/comment/1841553#Comment_1841553

Enough to get a return on investment?

Jamie Hall · February 9

https://forum.heatinghelp.com/discussion/comment/1841586#Comment_1841586

probably not.

Steamhead · February 9

https://forum.heatinghelp.com/discussion/comment/1841593#Comment_1841593

Maybe not at today's prices, but fuel costs aren't going down………….

Jamie Hall · February 10

https://forum.heatinghelp.com/discussion/comment/1841619#Comment_1841619

I believe that the project is in Connecticut. Fuel costs are going up — slowly — but if you want eye-watering increases, try electricity around here.

Hot_water_fan · February 10

Fuel prices change daily. If you know future prices, please tell us so we can place bets.

Jamie Hall · February 10

https://forum.heatinghelp.com/discussion/comment/1841659#Comment_1841659

You have a point — which is why all the places I care for buy in bulk, in the spring. At least we know what we are getting into. (this year it was $3.19 per gallon) Electricity prices, on the other hand, only go in one direction — up — and we do get advance notice… sort of… Loots like somewhere around $.35 per kWh here in the Nutmeg State, starting this summer… might be as high as $.38, but probably not $.40 this year anyway.

Hot_water_fan · February 10

Paying $.14/kwh here (if memory serves me right). Your delivery rates are obscene.

EdTheHeaterMan · February 10

Back in the 1970s when we had the first oil embargo, there were three big things that allowed us to use less fuel. The first thing that everyone could do right away was to set the thermostat from 72° back to 68°. President Nixon got on television and told all us Americans to do that. the next thing was to get a clock thermostat and automatically set the thermostat to 63° when we went to sleep and were out of the house. The clock would bring the heat back to 68° before we wake up or got home from work. The third thing was to get an automatic vent damper for your furnace or boiler. There were all kinds of studies performed back then and it seems that all atmospheric Gas boilers have automatic vent dampers today. So that must work.

But the lowering of the temperature would save about 15% if you lowered the temperature just 5°. Well that mathematics works in reverse too. For every 1° you rase the temperature you will increase your fuel consumption about 3%. So by increasing the temperature from 66° to 68° you can expect a 6% increase in fuel usage, all else being equal. So based on 700 gallons for space heating you can expect an additional 21 gallons of oil, to increase the temperature 2°F. That will be over $60.00 to be comfortable for the whole winter. That about 67 cents per day. That's less than a Dunkin donut. And think of how much weight you will loose when you stop eating all those donuts.

Fuel Oil Usage.

Which Viessmann boiler to buy?

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