Is Solar Water Heating Cost-Effective in Cold Climates?

[Chi Meson]

I'm very excited. I just finished ordering all the necessary parts to install a solar water heating system. With the likelihood of electricity only getting more expensive, coupled with the likelihood of my 3 children getting bigger, It seemed like a no-brainer.

Who else has solar heat? Any good insights?

 

[Cyrus]

How much more expensive was it to refit your house with this than to go the normal route? Typically that stuff doesn't pay itself off until 10 years later.

 

[berkeman]

Who else has solar heat? Any good insights?

Were you able to get any credits or rebates on the system? Utilities often give you some money to do stuff like that, since it saves them money because they don't have to build as many new power plants. If you can get a credit of some kind, that makes the payback period quicker.

 

[Chi Meson]

How much more expensive was it to refit your house with this than to go the normal route? Typically that stuff doesn't pay itself off until 10 years later.

About $3500 for all the stuff. I'm looking at a 3-year payback. I think you are thinking of "off grid" PV systems.

 

[Chi Meson]

Were you able to get any credits or rebates on the system? Utilities often give you some money to do stuff like that, since it saves them money because they don't have to build as many new power plants. If you can get a credit of some kind, that makes the payback period quicker.

IRS gives a pretty good tax credit; $700 to $1000 I think. Connecticut doesn't seem to do squat for me though.

 

[Ivan Seeking]

What kind of system is it; a passive preheater?

 

[Chi Meson]

What kind of system is it; a passive preheater?

Active, closed-loop. Antifreeze is pumped through the collectors, and then through a special heat exchanger contained within an 80 gallon water tank. From there it goes into the existing water-heater. In winter months it will amount to a pre-heater, but for 4 to 6 months, it should provide so much hot, that an anti-scald valve has to be installed to mix it with incoming cold water.

 

[Ivan Seeking]

Very cool! [or maybe I should say very hot!] It sounds like you will be in hot water for many years to come. Please post now and then and let us know how it's working out.

Unfortunately, IMO, the cost for active solar or PV isn't justified where we live - too many cold rainy days. Of course, with the new PV panels active over several wavelengths, that may change soon. Also, I have considered that a low cost passive system could be worth the investment for a hot water preheater.

 

[russ_watters]

You spend $100 a month on hot water? Yikes. I can't imagine that for most families there would be such a quick payback.

Still, it certainly does have a coolness factor.

 

[Chi Meson]

You spend $100 a month on hot water? Yikes. I can't imagine that for most families there would be such a quick payback.

Still, it certainly does have a coolness factor.

$80 per month actually. Here in New England, we are paying 18 cents per kilowatt-hour, and costs will be rising. We've got 3 kid, two of which are sharing a tub (for now), and two adult runners at two showers a day.

I am as conservative (energy, not politic) as I can be: all our lights a CF, everything we run is "Energy Star" and high-efficiency as possible; we only burned half a tank of oiil this winter. We line-dry nearly half of our clothes (working on that too). OUr love of hot water is our major downfall, therefore we go solar.

Yes, we could stop showering, but then I wouldn't be allowed back on the forum (pee-ew!)

 

[russ_watters]

If you have oil, wouldn't it be a lot cheaper to run an oil water heater? Electricity certainly is the worst way to make a BTU.

I don't know what you pay for oil, but I found a current online price at onlineheatingoil.com of $2.37/gal. With an energy content of 138,690 Btu/gal (40.6kWh) and a low-end efficiency of 85%, that's the equivalent of $0.07/kWh electricity. So for probably only a few hundred dollars up front, you could cut your bill by more than half and pay back in less than a year.

Even without considering things like interest and inflation, your numbers as you stated them don't add up: $80/mo is a 3.6, not a 3 year payback of $3,500 if you assume you can use use the solar heat all the time, which you can't. Now perhaps if the real payback ends up being 5 years it is still worth doing, but I'd really want to know before spending the money.

I don't mean to rain on your parade here, but I don't like seeing people make potentially bad decisions based on overexcitement about environmentalism.

 

[Evo]

Good heavens, $80 a month just to heat water? I have an all electric house and with four of us living here at one time and with a very wasteful now ex husband that would take a 20 minute HOT shower (he would only stop when the hot water ran out, then take a HOT Bath, then another HOT shower and do this twice a day, with tons of laundry, dish washing, etc... we only spent a fraction of that on hot water.

Based on the total amount of the electric bill during mild temperature months when we weren't running the air conditioner or heater much, my guess would be that hot water might account for $20.00 per month.

Right now my average electric bill is $50 per month and I have a rather large house (4 bedrooms, three bathrooms).

I do have very energy efficient electric appliances which I guess helps. My girlfriend at work uses gas for heating and cooking and her last bill was $300 just for her and her son, so I guess I must be unnaturally frugal.

How did you manage to actually measure your hot water heater usage?

 

[Chi Meson]

If you have oil, wouldn't it be a lot cheaper to run an oil water heater? Electricity certainly is the worst way to make a BTU.

I don't know what you pay for oil, but I found a current online price at onlineheatingoil.com of $2.37/gal. With an energy content of 138,690 Btu/gal (40.6kWh) and a low-end efficiency of 85%, that's the equivalent of $0.07/kWh electricity. So for probably only a few hundred dollars up front, you could cut your bill by more than half and pay back in less than a year.

Even without considering things like interest and inflation, your numbers as you stated them don't add up: $80/mo is a 3.6, not a 3 year payback of $3,500 if you assume you can use use the solar heat all the time, which you can't. Now perhaps if the real payback ends up being 5 years it is still worth doing, but I'd really want to know before spending the money.

I don't mean to rain on your parade here, but I don't like seeing people make potentially bad decisions based on overexcitement about environmentalism.

Back off dude, you're clouding my collectors man!

You are missing a bit of the math: the federal incentive is 30% of the system as a tax credit, so that's at least $1050 off the top right there (the $700 I stated earlier was from my first estimate, when I was thinking of a smaller system). THere is also supposed to be a local rebate from the power company, but this amount is unclear. So Yeah, I am still predicting a payback between 3 and 4 years. Call me an optimist, but don't call me naive.

 

[Ivan Seeking]

Electricity is only the worst way to make a BTU when viewed as a zeroth order problem - factor in the reduced CO2 and toxic emissions and the reduction in demand for imported oil. Eventually this will all have a specific monetary value. With a house full of kids, this is clearly a valid consideration now.

 

[Chi Meson]

Good heavens, $80 a month just to heat water? I have an all electric house and with four of us living here at one time and with a very wasteful now ex husband that would take a 20 minute HOT shower (he would only stop when the hot water ran out, then take a HOT Bath, then another HOT shower and do this twice a day, with tons of laundry, dish washing, etc... we only spent a fraction of that on hot water.

Based on the total amount of the electric bill during mild temperature months when we weren't running the air conditioner or heater much, my guess would be that hot water might account for $20.00 per month.

Right now my average electric bill is $50 per month and I have a rather large house (4 bedrooms, three bathrooms).

I do have very energy efficient electric appliances which I guess helps. My girlfriend at work uses gas for heating and cooking and her last bill was $300 just for her and her son, so I guess I must be unnaturally frugal.

How did you manage to actually measure your hot water heater usage?

I did the math, and a 20 minute hot shower in my house costs at least 83 cents for the heat; that's about $25 a month. I'd guess we have an average of 45 minutes of shower time per day, plus one 10 gallon bath. (all these are low estimates--water is our dirty luxury)

Our cold water is very cold; even in the summer it is rarely above 50 F. Folks who have well-water get an unseen benefit in the heat they get from the earth; we're downstream from a frozen resevoir.

 

[Evo]

Our cold water is very cold; even in the summer it is rarely above 50 F. Folks who have well-water get an unseen benefit in the heat they get from the earth; we're downstream from a frozen resevoir.

Ah, that makes much more sense, it would cost you much more to heat your water. In the summer the water is warm enough that I don't even use heated water much.

Sounds like you made the right choice.

 

[Chi Meson]

Ah, that makes much more sense, it would cost you much more to heat your water. In the summer the water is warm enough that I don't even use heated water much.

Sounds like you made the right choice.

Well, at least I really, really, really want to think so.

I just rechecked the estimate of the bathtub volume; half-filled it's about 50 liters, so the 10-gallon per tub estimate is low. I'm calculating a low-estimate of $70 per month on hot bathing water alone, not including laundry, hand-washing, dishwasher, heat loss in the pipes, etc.

 

[TuviaDaCat]

here in israel every home has one of this, most of the time we have sunny days, so its quite efficient...

sounds expensive btw, here it costs about 200 dollars for 120 liters, a bit less, though its without all the plumbing and the installation..

 

[Chi Meson]

here in israel every home has one of this, most of the time we have sunny days, so its quite efficient...

sounds expensive btw, here it costs about 200 dollars for 120 liters, a bit less, though its without all the plumbing and the installation..

The big difference in price has to do with the fact that I live in a zone that goes well below freezing. In Israel you would only need a single collector that is plumbed in-line with your incoming water. That is, the hot water you actually use has gone through the collector. Here, we need a closed loop of anti-freeze that goes through a special heat exchanger tank to warm the incoming water. That tank alone cost the first 1000 bucks.