Oil Indirect DHW - Cost Analysis Help

[bryankloos]

Guys,

I had another oil delivery this week and pulled out the spreadsheet. What caught my attention was the amount of oil I was using over the summer which presumably only heated DHW through an indirect DHW tank heated with the oil burner.

From the time we bought the house this summer through our first oil delivery (June 14th - October 24th) we burned 142 gallons of oil over the 134 day period, to give me 1.08gal/day which at $3.54 costs me $3.81/day to heat my hot water. The above calculation of course assumes I didn't use any heat towards October which probably isn't true but I don't know when I first started using heat, so lets round down the numbers in our heads a bit...

This to me seems crazy. Is it possible that I am paying this much just to heat my water? That's almost $1400/year just to have hot water???

Fortunately the oil consumption has been pretty low since installing the insert in November but I am still burning oil to heat the water. That will hopefully change next year when I install a gasser but that is down the road...

So, armed with the above data, what would you do?

1. Switch over to electric?
2. Suck it up until I install a gasser?
3. Tell the wide and kids to take cold showers?
4. Some other option which makes sense financially and keeps the family happy and warm...

If it helps, I have a Veissmann Vitorond 100 with a Reillo burner, running 87% efficiency with the unit being about 8 years old.

All input is greatly appreciated.

Many Thanks,

Bryan

 

[ewdudley]

Your DHW oil use is typical, a gallon a day. I think some can do much better with a low-mass cold-start boiler and an indirect tank. Typical electric DHW load is 6-8 kWh / day, $30 / month @ $0.15 / kWh, less with low-volume shower nozzles, tank insulation, and heat traps in tank plumbing. DHW from a gasser is a nice bonus, but is not a justification for one.

[Edit:] Check out discussion of GE GeoSpring below!

 

[infinitymike]

If you are definitely getting a gasser than I would wait.

I have an indirect DHW that can be heated by the oil back up or my gasser.
I choice to heat my DHW all summer with wood. I don't have storage but
Its real simple, especially with the wife home all day.
A 15 minute batch fire in the morning and the tank is good for most of the day unless wife does a lot of laundry and she loves to use hot water for most loads, then she will do a small batch burn.
Then another small batch burn later in the evening for showers.

If you do a gasser with storage it will be even less work for DHW as far as I have heard.

 

[maple1]

Echo ewdudley

I'm not familiar with your boiler - but I suspect it isn't a low mass cold start boiler?

I replaced our oil/wood combo boiler that did DHW with tankless coil, with an electric 80 gallon hot water heater, about a year and a half ago. We went from about 3/4 tank of oil (say 150 gallons) to do just our DHW when not heating the house (say maybe 5 months a year), to about $30/month (@ 0.17/kwh) to do our DHW when not burning wood (this past year that was only July & August). Very similar to ew's numbers. That's a family of 5 - one a teenage girl.

Depending on your boiler controls and how exactly it's working, you might be able to cut some oil use by lowering it's temps, or converting somehow to cold start operation. But, you could also put in a new electric or HPW water heater now and just turn the oil boiler off (if you really don't need it for house heat) - and plumb it to get heated also by a new wood boiler when you get to that point.

In other words - I'd try to do something about it right now & not wait for my new gasser, especially if you aren't sure you'll have a new gasser within the coming year. At over $100/mo for oil, you'd be looking at a pretty short ROI time - likely less than a year even if you go for a more expensive HPWH especially if you have incentives available.

 

[Coal Reaper]

last summer i heated DHW with my newly installed gasser and 1000gals of storage. 5-6 days between burns. i figured about a cord for 3 months but didnt keep track of it well. while this is better than oil, i wish i had an electric water heater and will likely replace with one when my indirect is at the end of its life. my vote is to get the electric going ASAP. look at ones with a coil as well as the electric element so that for winter you can tie it into the gasser when you get it.

 

[GENECOP]

Same here last year, this year the Geyser Heat Pump will make my domestic during the warmer months....

 

[johnpma]

If it's only a couple people using hot water then I would look at the new hybrid heat pump hot water heaters. The 50 gallon units are about $1100.00 but you get most of that back at both state and fed levels. They estimate the cost for hotwater at less than $1.00/day for a small family. Pretty much a no brainer if you are a small family and 50 gallons will work for you. I just installed a Whirlpool energy smart unit but do not have numbers yet. We are a family of 5 and need 80 gallons. The energy smart monitors usage by computer and makes hot water previous to its monitored times. Works like a charm so far!!

 

[bryankloos]

Thanks for the replies guys.
I'm currently at 0.11/kwh, so it seems electric may be the way to go. I plan on installing the gasser, but it may get put off until the year after next. We just moved in and need to replace the roof and get the house painted, which are priorities at this point.
That said, I like the idea of an electric unit with a coil for heating during the winter while the gasser is up. In the summer I would have the option of heating with wood or electric. Seems sensible.
What type of unit would you recommend I look at in the 80 gal range?
The knowledge of this board always amazes me.
Thanks!
Bryan

 

[ewdudley]

electric may be the way to go. I plan on installing the gasser, but it may get put off until the year after next.

I don't know if it's been tried, but I would think that an electric heater tank in a closet one floor above storage, heated by a sidearm above storage and below the electric heater tank would work real well. Gravity flow, no pumps, no controls except anti-scald mixer leaving electric heater tank. Maybe something to consider when placing your electric tank.

 

[bryankloos]

Guys,

Do you know of any Hybrid or "Smart Electric" heaters that have a coil integrated?

Thanks,

Bryan

 

[Coal Reaper]

(broken link removed to http://www.ebay.com/itm/Solar-Hot-Water-Tank-with-Electric-Coil-Backup-115-gallon-/221259624977?pt=LH_DefaultDomain_0&hash=item338419f211)

this is what one of the members here pointed me to (sorry, i forget who). quite expensive but all stainless so should be the last one you ever buy. oventrop is made by another company or something like that. one of them also as dual coil models.

 

[maple1]

Don't overlook what you can do with a regular electric water heater, and separate heat exchangers, if you find a coil-in tank too expensive.

Sidearms work very well, very simply, using convective flows & no pumps, during the heating season. You need to get all the components oriented right for that to work optimally - paying close attention to vertical alignments and stacking them (horizontal separation = bad).

If you wanted to keep the door open to heating DHW from storage in the off-heating season, then you can incorporate a flat plate HX & pump the domestic side.

Either one of those can be added later to a regular electric tank - try to put the tank in the right place for those later add-ons now, and leave some stubs & ball valves. Also, I went with a bottom-feed tank to make it a bit easier (for me) - that is likely a necessity if you wanted to add a sidearm later, although you could likely utilize the drain port if you wanted to.

The very first thing I would do though is check out what incentives are available to you for a HPWH - if there are any at all, it could make that the 'no-brainer' choice. And you can also add HXs to one of those later too if you still wanted to do your DHW with wood later.

 

[bryankloos]

Looks like my local POCO has a $400 rebate for HPWH.
I wonder if the Fed will continue with the $300 rebate during 2014?
A combined $700 in savings would be a good down payment on the system. bringing the ROI to under 2 years...

 

[Bob Rohr]

Looks like my local POCO has a $400 rebate for HPWH.
I wonder if the Fed will continue with the $300 rebate during 2014?
A combined $700 in savings would be a good down payment on the system. bringing the ROI to under 2 years...

Don't forget solar thermal. One 4X8 or 4X10 panel will provide plenty of DHW for a family of 4 with a 40- 60% solar fraction, depending on your location of course.

If you are a DIYer and can install a system yourself the numbers work out. If you like to build stuff, builditsolar.com has plenty of homemade collector plans.

A dual coil indirect tanks makes it easy to have SDHW and backup in one tank. Or solar coil with and upper electric element for backup.

 

[moey]

Thanks for the replies guys.
I'm currently at 0.11/kwh, so it seems electric may be the way to go.

You may want to double check your rate that seems really low for NE. Total divided by kw used. Firing a boiler to just make hot water is inefficient I dont care what the oil man says. Its like driving a semi to the corner store rather then a compact the compact gets much better mileage.

I have a 80 gallon electric never run out family of 4. I currently have it off my geothermal system makes the hot water in the winter. I'm contemplating getting a HPWH to act as a supply for the 80 gallon electric so in the summer I can do the same.

 

[STIHLY DAN]

Looks like my local POCO has a $400 rebate for HPWH.
I wonder if the Fed will continue with the $300 rebate during 2014?
A combined $700 in savings would be a good down payment on the system. bringing the ROI to under 2 years...

at $700 off and purchase of $1100. Thats $400 remaining, then $200 a year instead of $1400. Thats $1200 less out minus the remaining $400 For a profit of $800 the 1st yr. ROI would be 4 months.

 

[bryankloos]

Yup... .09 Generation and .02 Delivery = 0.11/kwh
I had an energy audit today and they also recommended ditching the oil DHW and moving to on-demand propane or HPWH.
The Whirlpool 80 gal looks pretty decent at about $1800. With a 10% coupon and the $400 rebate that brings me to $1220 which I would install.
They also suggested spray-foaming my attic roof decking making it conditioned space. They have a rebate that will pay for 50% of the job. Seems interesting...
I'm leaning towards the HPWH as it will work with the current system and can still be used down the road when I get the gasser.

What do you estimate the annual cost of running the HPWH would be for a family of 2 adults and 2 small children?

Thanks,

Bryan

 

[Ram 1500 with an axe...]

I don't know what a gasser is.... That being said.... Get an electric water heater.....

 

[STIHLY DAN]

My bill went down $7 a month may thru sept. ( did not have to run dehumidifier ) Oct was up $20 nov thru march even, ( wood furnace made a bunch of H20 ) April up $20. Thats a family of 5, 3 being teenagers, and the wife liking her 60 gal baths. @ .19 kw. So $5 a year. I'll take it.

 

[Ashful]

From the time we bought the house this summer through our first oil delivery (June 14th - October 24th) we burned 142 gallons of oil over the 134 day period, to give me 1.08gal/day which at $3.54 costs me $3.81/day to heat my hot water.

Our usage is similar, with our 1986 oil-fired boiler and DHW off the boiler. Summer time usage bottoms out around 1 gal/day... probably actually lower, since there's at least some heating days in each of those low points. We average just below 7 gal/day mid-winter with one stove going.



I was able to push my gal/HDD way down in fall 2013, running TWO stoves 24/7, but quickly realized I was going to run out of wood. So I dialed back to just one stove during the week, firing the second stove only on weekends, which is the reason for the up-tick in the gal/HDD curve in the early part of 2014.

 

[BrotherBart]

At current prices that gallon a day is our entire electric cost in this all electric place. In winter with the wood heat and a space heater in the fartherest bedroom.

Heating water with a boiler is just plain nuts.

 

[Ashful]

Yeah, I'm beginning to see that. Never gave it an ounce of thought before. Unfortunately, our house is plumbed for a boiler, and natural gas is not an option where we live. I can't imagine producing our BTU needs with wood (15 cords / year at 75% average efficiency), so we're sort of stuck with oil for heat. I guess the thinking was that as long as the boiler's here for heat, you might as well get the DHW water off of it.

I suspect that a more complete analysis would show we pay less to heat our water in winter, than in summer. In summer, we're keeping that lossy boiler warm, solely for the sake of powering a heat exchanger and heating our DHW. In the winter, the boiler is already warm (actually, kept at a higher temperature than in summer), and all losses are going into heating our house (rather than just making the AC work harder.

Not justifying it... just thinking out load.

 

[JP11]

Yes.. saying that your a gallon a day all year round is not accurate. The biggest waste in summer DHW production is the fact that you have to heat your boiler first, THEN it starts heating your DHW.

Now in winter.. your boiler is running much more and is likely already warm, or the boiler will get called on for a heat load soon. In the summer.. your demand for hot water has long periods between firings, thus wasting the heat in the boiler jacket.

I tend to at least ATTEMPT to cluster dishes, laundry, and showers together. Even just when using the wood boiler. It's the most efficient use.

In a perfect world.. middle of summer I would probably give up and just use electric. BUT.. I have this fancy new wood boiler.. it works fine for a small fire every few days. The wife has gotten into a neat spring hobby. She walks around the yard with the dogs collecting sticks (gotta pick up all the stuff anyway) and heats hot water with it. There's a lot of sticks around the edge of the lawn with a couple acres of grass.

JP

 

[velvetfoot]

I don't know why you can't graft on an electric water heater. Here is a pic of what I did. Of course, things may have to be moved with my "gasser" plans.

edit: I've since wrapped it in fiberglass with a shiny bubble plastic cover. Maybe not super in the looks department.

 

[maple1]

Unfortunately, our house is plumbed for a boiler ...

I would say there's nothing unfortunate about that. You just need the right boiler.