hot water - thinking of going electric

My electric bill went up about $50 when I shut down my boiler and started the electric hot water. The boiler was burning 1 gallon per day to make hot water, $120 of oil per month for 2 people.

If your hot water is heated by an indirect tank like my backup try putting a small timer in the DHW control circuit. I let the DHW call for heat for 2 hours in the morning to reheat the tank and then its off again until the next day. It works out for me, it seemed that anytime I ran even a small amount of hot water it would make the boiler fire even though there was plenty in storage. I used a small electronic Intermatic lighting timer that cost a round $20.

This will not work if your coil is in the boiler, but if you have an indirect it might be worth a shot. I did this for a neighbor and he claimed he saved a ton of fuel this summer.

My oil company said that they typically see 20 gallons a month for hot water for a typical family. Ours was EXACTLY that - 100 gallons for five months.

If you have a wood boiler and your hot water is from a coil in your oil boiler, there are some other considerations:

1) You want to make sure that you can let your oil boiler go cold without hurting it. Some definitely are OK with going cold, but some MAY have issues.

2) With an electric tank, you can do a sidearm heat exchanger to heat your DHW tank from your wood boiler, preventing the tank from using electricity much of the time. This does require an anti-scald valve on the tank outlet, though.

3) Electric tanks typically have much lower standby losses than oil boilers with internal DHW coils.

Concerning the breaker box, Square D makes breakers that operate a pair of 120 V circuits but only occupy one slot in the box. You could use two of them to make room for your elec water heater breaker. You do plan to use the new wood boiler for DHW don't you? I love my sidearm setup, the breaker on my elec water heater hasn't been on for years.

If you are going to have problems with letting your oil burner go cold, when will you have them? As soon as it goes cold? or as soon as you try to turn it back on?

If you do end up problems, are they fixable? or do you basically end up replacing the boiler?

MrEd said:

If you are going to have problems with letting your oil burner go cold, when will you have them? As soon as it goes cold? or as soon as you try to turn it back on?

If you do end up problems, are they fixable? or do you basically end up replacing the boiler?

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There can be condensation issues running cold domestic water through a coil in a boiler that is not hot. If your boiler has a coil and is not hot you should bypass it and go straight to the electric heater.

futureboiler said:

nofossil - i didnt know that one...about the cold boiler/cold water thing..

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TarmSolo60 actually gave you a more useful response on that one, and it's something I never thought about. I don't have a DHW coil in my oil boiler (I have an indirect tank) so I never thought about the condensation issue. It makes a lot of sense, though.

Some people here have reported leakage problems when allowing oil boilers to go cold and then restarting them, and some have described certain oil boilers as 'cold start'. My oil boiler is nothing special, and certainly doesn't describe itself as a 'cold start' unit. I've used it that way for 20 years with no problems. It may be that the boilers that have had issues were on their last legs anyway, but I try to be careful when giving advice in areas where I know nothing.

The condensation issue sounds like a real concern, though. At least it should be easy to avoid. If you have the electric, there's no reason to leave your oil boiler coil connected.

If you go electric, take the time to be really efficient, and you may save up to 1/2 the electric cost you otherwise would use. Regardless of what the dealer claims, do the following:
1) raise the hot water heater off the floor on a 2x6 frame and insulate between the bottom of the hot water heater and the floor.
2) wrap the tank sides and top with 6" of fiberglass insulation, and then wrap that with the foil bubble wrap, taping all seams.
3) install real heat traps on both the hot and cold water lines, and don't rely on the ones integral to the tank. A heat trap is a rise in the pipe of at least 18", followed by two elbows to turn the pipe down at least 12", and then elbows to turn the pipe back up and to the plumbing lines. The heat traps stop thermo-siphoning.
4) insulate all the hot water lines you can get to with foam pipe insulation.
5) don't use a circ pump to circulate hot water for "instant on" hot water at all spigots. You lose lots of heat through circulating hot water.
6) get used to using cold water for the otherwise brief needs for hot water, such as for washing hands or rinsing a dish. No need to run lots of water to get a few seconds of hot water.
7) if you haven't already done this, get low flow spigot aerators and shower heads.
8) conserve use of hot water as much as possible.

We did the above and our electric usage dropped 50%.

I'll add one more to jebatty's excellent points:

If you have the opportunity, install the DHW tank as close as possible to the point of most frequent use. For us, that's the kitchen. We have less than 6' of 1/2" pipe between the hot water heater and the kitchen sink. Saves a lot of hot water.

...and one more. Our "main" hot water heater is located in the basement right under the bathrooms, where most hot water is used -- quick on by reason of location. Our kitchen is a long ways away, so instead of feeding hot water from the main tank, I installed a separate 5 gallon hot water in the basement right under the kitchen sink/dishwasher. Also now quick on. 5 gal is enough for almost everything, and if it isn't, it recovers very fast. Also insulate this tank with fiberglass and foil bubble wrap, and the hot water lines, and the pipes.

atlarge54 said:

Concerning the breaker box, Square D makes breakers that operate a pair of 120 V circuits but only occupy one slot in the box. You could use two of them to make room for your elec water heater breaker. You do plan to use the new wood boiler for DHW don't you? I love my sidearm setup, the breaker on my elec water heater hasn't been on for years.

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similar breakers that allow several circuits to fit into the space of a single breaker are also available from other makes/ configurations of breakers besides Square D-- I know that several manufacturers make them for the "ITE" pattern breaker boxes, and I have used them with success.

for a hot water heater, you're going to need 240 volts, which actually means you'll need to pull from both of the 2 separate 12 volt "legs" of the panel's "bus bars" which means you'll need something that, at least under the Siemens brand that I've often used, is referred to as a "QT Triplex":

see:

http://www.sea.siemens.com/SpeedFax06/Speedfax06files/06Speedfaxpdfs/06Speedfax_01/01_25.pdf

you also need to make sure that shoehorning the new load of the water heater into your existing panel, when combined with the other electric loads served by the panel, won't exceed the rating of the panel (which is not just about how many breakers you can squeeze in, but also the total max amperage load that the panel can handle) In some situations you can have plenty of physical room for more breakers, but already be over the panel's rated limits, and in others, you can have a shortage of physical room but plenty of headroom on actual amerage of all your loads compared to the panel's rating.

You may be fine, it'll depend on your details of your panel and other loads, but if the above seems like indecipherable mumbo jumbo, call a good electrician.

ok, here is what I did this summer to get a handle of the true cost of my oil fired hot water. First: No to automatic delivery; Second a broom handle with clear measurements on it. Third: dip the tank about once a week or so for the summer and logged down the readings. I used 1 gallon of heating oil per day. I have a 50 Gal. Top Performer.

My house is new so I'm not sure if it's worth pulling in a "on demand" heater or an electric heater. So for the family of 5 I spend approx. $120 per month on HW.

My wood boiler is getting hooked up later this month when I have the cash, then I'll see the real savings.

Kevin

These costs for hot water from an oil fired boiler blow my mind. There are just two of us, wife and me, and our electric cost for hot water averages $4.50 a month. Before doing the conservation items mentioned in my posts above, it was about $9.00 a month.

Which leads me to the conclusion that using an oil fired boiler, and probably any boiler, to produce hot water, other than during the heating season, maybe, is a horribly inefficient was to provide hot water.

jebatty said:

These costs for hot water from an oil fired boiler blow my mind. There are just two of us, wife and me, and our electric cost for hot water averages $4.50 a month. Before doing the conservation items mentioned in my posts above, it was about $9.00 a month.

Which leads me to the conclusion that using an oil fired boiler, and probably any boiler, to produce hot water, other than during the heating season, maybe, is a horribly inefficient was to provide hot water.

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Either you have the lowest electric rates in the world, or you use hot water by the teaspoon.

I've heard an estimate of about 60,000 BTU/day as typical hot water usage for a family of four. Ours with a family of five including three teenagers seems to be right in that range. Electric is 100% efficient, but that still works out to 500 kWh/month. At our rates that would be over $50.....

Electric usage for hot water last three months was 123, 145 and 131 kwh; our rate is about 4 cents/kwh. It is an off-peak rate, only after 11:00 pm and before 7:00 am. Normal rate is about 11 cents/kwh.

The key thing is usage, which is about 1/4 of nofo's, and was twice as much before the conservation measures. Given that we are a family of two, usage would be about 250 kwh/month pre-conservation, so we are "right-on" as to average usage.

nofossil said:

jebatty said:

These costs for hot water from an oil fired boiler blow my mind. There are just two of us, wife and me, and our electric cost for hot water averages $4.50 a month. Before doing the conservation items mentioned in my posts above, it was about $9.00 a month.

Which leads me to the conclusion that using an oil fired boiler, and probably any boiler, to produce hot water, other than during the heating season, maybe, is a horribly inefficient was to provide hot water.

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Either you have the lowest electric rates in the world, or you use hot water by the teaspoon.

I've heard an estimate of about 60,000 BTU/day as typical hot water usage for a family of four. Ours with a family of five including three teenagers seems to be right in that range. Electric is 100% efficient, but that still works out to 500 kWh/month. At our rates that would be over $50.....

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There was an older post at https://www.hearth.com/econtent/index.php/forums/viewthread/19035/P30/ where we played around with cost comparison between electric and oil DHW generation. I roughly calculated that oil would have to reach $5.00/gallon and electricity to be below 13 cents to be about even. No guarantees on those numbers. My take is that when you use very little hot water an electric heater will make sense especially with the equipment involved. It just depends on the current price of the fuels. Actually, overall electricy used for heat is very inefficient when all factors are taken into account. A combustion source is still used to make the electricity and then transmitted over a long distance has its inefficiencies. Anyone lucky enough for 4 cents/kwh should dump any other means of generating heat. My electric price as of right now is 18.6 cents/kwh. There is a electric boiler on the market designed for off-peak heat generation that stores the heat in a high temperature ceramic storage. I don't have an off-peak option.

This does make me think that I should hook up the electric elements in my solar preheat tank and shut down the boiler for the summer. I'll have to do a little calculating. Probably a moot point since my solar system will up and running very soon.

That being said I did calculate jebatty's hot water consumption based on 133 kwh/month average. Assuming you need to raise 50 deg water to 120 deg and there is 3413 btu's/kwh, that means you used about 25.9 gal/day. Impressive but not realistic for a family with teenagers as nofossil and I have. Just to help you out nofossil, 25.9 gallons is equal to 19,905 teaspoons. LOL.

Mike

I agree that overall electric is not efficient. Quite awhile ago I did an efficiency evaluation of electricity, including coal generating plant efficiency and line transmission loss, but not including costs to mine coal and deliver to the generating plant.

DOE estimates average coal generating plant efficiency at 33% (nuclear is about the same), and line transmission losses range between 8-15%, meaning average electric efficiency delivered to the home is about 30%. Electric resistance efficiency for electric delivered to the home iis about 98-99%.

Technology exists, but is not in place in any material way, to raise efficiency by about 15-20% (ultra critical plus dual stage).

For the homeowner, all that one can do is first conserve, second insulate, third use the most efficient appliance one reasonably can afford, and fourth lobby at all levels to force more efficient energy production using sustainable resources.

jebatty said:

I agree that overall electric is not efficient. Quite awhile ago I did an efficiency evaluation of electricity, including coal generating plant efficiency and line transmission loss, but not including costs to mine coal and deliver to the generating plant.

DOE estimates average coal generating plant efficiency at 33% (nuclear is about the same), and line transmission losses range between 8-15%, meaning average electric efficiency delivered to the home is about 30%. Electric resistance efficiency for electric delivered to the home iis about 98-99%.

Technology exists, but is not in place in any material way, to raise efficiency by about 15-20% (ultra critical plus dual stage).

For the homeowner, all that one can do is first conserve, second insulate, third use the most efficient appliance one reasonably can afford, and fourth lobby at all levels to force more efficient energy production using sustainable resources.

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Right on..........

Mike

looked at a product by grundfos that looked interesting. It hooks to whatever hotwater tank you have and then you put a thermal valve on your furthest plumbing fixture, so that when you turn on the hot water it bypasses the "cooler" water in your lines to the cold lines until the water reaches I think 90 degrees then allows it to close. There is a pressure pump that kicks on when there is an open valve.
I don't understand where that pressure goes in your cold side? They claim it saves thousands of gallons a year in water which if you are on rain catchment like me it is something to consider?

If I were you, I wouldn't go electric.
Come 2010, electricity might get deregulated in PA and the says goes that the bill should jump from between 50% to 100%. If you already have a gas line, it might be a be a better option to go for gas hot water boiler.

I was considering a gas water heater, but the installer advised against it. I currently have a oil-fired water boiler for heat. According to him, if I install a separate gas/electric water heater, I will have to switch off the oil-fired water boiler to save on oil. Leaving the oil-fired water boiler off for a long time will result in rusting in the water tank inside the boiler and result in more maintenance of the oil-fired boiler.

I've decided to bite the bullet - using the oil boiler for hot water. With the winter around the corner, I'm going to use the oil-fired boiler for hot water. Hope it won't end up costing me too much as this is my first winter in this house.

I switched from electric to gas in Feb 08 and I was using 700kwh a month water usage for 3 of us. It was costing about $120/month gas cost me $55/month. My parents have oil with an indirect tank and use about 20 gallons of oil/4-5 weeks in summer still cheaper than electric. I am in upstate NY so I not sure what other states have for electric charges but i plugged mine into a calculator with tax,delivery and supply charges and it came out pretty close with NG being cheapest and then oil then electric. I am not a fan of electric.