Saturday, December 20, 2008

Running the Numbers

I've finally put together some graphs of my electrical and gas usage. Please note, that I know our electrical usage has gone up considerably because in Sept we had a new baby and we use cloth diapers; i.e. the dryer has been running non stop.

That being said, let's take a look at our gas usage for the past 6 months.

In May, our furnace started leaking gas (it's old). I didn't catch it for a day or 2, so that's the reason for the high gas usage. However, when looking at the rest of the months, it's obvious how much gas we saved compared to traditional water heating. Also, you can see gas usage going up in Oct. probably because I turned up the heater with the new baby in the house

Electric usage on the other hand has gone up, which is to be expected since the system uses an electrical backup. Obviously the colder and rainer it get's, the more we use the backup. If you read my other post, I think I could have tuned the system better last summer .

When the electrical backup kicks in is a mystery I'm just starting to solve. In Nov., I purchased a monitor which just hooks on over ones meter. It works great and has helped us to understand how we can avoid using the backup. It's called a Home Energy Power Cost Monitor and I found terrapass had the best price on it.

One important issue the Power Cost Monitor has brought to our attention is the fact if we just pull up the bathroom sink handle in the middle (for warm water), the water heater backup comes on if the tank is a bit cold. Basically, as soon as there is hot water flow, it will kick in. Most of the time, the water isn't on long enough for us to get the hot water in the sink so we're wasting power and hot water. I think I may switch out those combo knobs for ones with separate hot and cold water.

Finally, since my gas usage has gone way down, but my electrical usage has gone way up, I've taken my electrical and gas usage for 2008 and mapped them to 2007 prices.

Once again, I'm not sure this graph is fair since my electrical usage has significanly increased since Sept due to the drying running much more. Also, 2007 gas prices seemed to be higher then 2008 (which skews the results a bit). But, I'm thinking that if you want a solar water heater in order to save money in the long run, it may not be the way to go due to the high inital cost of the system. However, since I do plan on eventually putting up solar panels to offset my electrical, the cost of the solar water heater in that situation may pay for itself quickly.

I'll keep running the numbers and updating the charts as I figure out best practices over the next 6 months. Hopefully, by next year I'll have a system in place which will make significant difference in our electrical usage. At this point, I think I'm about breaking slightly north of even with my electric bill (when I consider the higher dryer usage).

Wednesday, November 12, 2008

making a difference on the electric bill.

The one thing that this water heater setup doesn't come with is probably the most important part; a user's manual. I was given a bunch of manuals, but they were mostly installation manuals for the various components. There's no comprehensive manual from velux which covers the basics such as:
  • ideal settings for your climate or weather
  • when does the electrical backup kick in
  • how does one optimize performance.
In the first month, we didn't do anything different from our normal routine. we did our wash later in the day, started the dishwasher late at night, and took our showers in the morning. As a result, our electrical usage became very high due to the electrical backup always kicking in.

Furthermore, the tank and control unit were both set to top out at 140 degrees F, although the tank can go up to 180. I was told this was done because if the panels get too hot, the system will try to protect them by pumping glycol through them (thus heating up the tank above your settings).

In the first place, the panels got to 375F in the summer when it was 110F outside and the pump never kicked in to lower the temperature (there's no instruction manual to tell you when it's supposed to kick in). In the second place, the tank seems to have a hard temperature setting which isn't effected by the control module. And in the third place, when I finally was able to find a little more detail on the tank manufactures web site, they specifically say to set your tank to above 160F in order to optimize performance. I personally think the system as a whole was configure wrong in that I think the tank should be set to say 170 but the control unit should be set to a max of 140 in order for the protective backup to kick in if the panels get too hot.

So, now we do simple things, like check the temperature of the tank before we run the dishwasher and try to start doing laundry in the late morning. These minor lifestyle changes made a measurable difference and started to drop our utility bills to lower then the year before. However, the biggest difference came after messing around for a couple months trying to increase the max temperature in the tank (I'll post these instructions in my next post since there's no comprehensive manual which will tell you how).

Ideally, I think one should have summer settings and winter settings. In both cases, I think the tank should be set to 175F and one simply adjust the conrol unit to the max you want (say 150 for the summer and 165 for the winter).

Thursday, September 11, 2008

How it works

So the installers buttoned up all the final issues and I'm left with my solar water heater.

First note the black cables coming down from the roof into the black box. Those are the glycol lines transferring heat from the panels into an heat exchanger inside the monster 120 gal water tank. The black box they run through is control computer and glycol pumps. The bright cyan tank is the glycol overflow for when the glycol expands when it becomes very hot. There's a clear container on the floor; this is the last ditch glycol expansion container if for some reason the cyan tank fills up and the pressure in the line goes above 6 bar. Since we installed the system, it has got to 110 degree at my house and system pressure got to 5.5 bar (my panels were 375F). still, no overflow.

The pipes onto of the tank are the hot and cold water. note the cross connect between the pipes; there's a valve on the hot line which only allows 120 degree F water out of the system. the valve just mixes in cold to always output 120 F water.

the tank is factory set to 140F, which means that the tank will heat the water inside to 140F . once the water is 140 (which in the summer happens around 11am) the pumps stop pumping the glycol through (raising the bar pressure as the panels continue to heat).

From what I can tell, if you want hot water when the tank is colder then 120, then the electric backup kicks in and heats the water from whatever temp it is at to 120. You don't need a whole new electrical service like you normally would for an electric tankless system because you're heating water which is already hot and not from the cold tap. That said, I'm sure that the whole thing would fall apart if I were to use both showers and wash some close in hot water; i.e. the amount of flow out you could achieve while keeping the water hot is probably limited since you only have 20 amps to play with.

I should also note, that the coldest I've seen the water at is 89F the day after we got the system and we hit a cold snap. the water in the tank didn't have a chance to heat up until the next day, which was also overcast but good enough to get the tank to 120. even when the tank was at 89F, we still have hot water at 120F.

When I got my first PGE utility bill I was ready to see a significant savings; but that's not what happened. Instead, I ended up paying more for additional electricity used by the system then the natural gas the system was not using; what happened...... I'll explain this in my next post.

Tuesday, August 12, 2008

The install

The install took 2 and a half days to complete. With these panels, there's quite a bit involved from multiple professions. I think this may be a reason why it's difficult to find integrators.

Here's my quick list of my perseption of how the job breaks down for the integrator:
  1. roofing : these guys need to cut up your roof and install the panels
  2. plumbing : there's a very good chance, because the tanks are so big, that you'll need modify your existing plumbing
  3. electrical : for the 220v tankless backup and the 110 pump
  4. gas : if you have an old water heater you are replacing, you need someone to plug the gas line.

My integrator took care of the whole install. They were mainly roofers and skylight/solar light installers so the panel installation was top notch. The integrator hired an electrician so that part looked and worked great. However, the plumbing was done by "this guy" that the integrator knew instead of a contracted plumber.

If I were to do this again, I would insist on the plumber. maybe it would bump the price up a couple hundred bucks, but it would have been worth it. First off, I feel that the route they took to get the pipes from my old water heater to the new one (up through the attic) was the wrong way to go since it adds length to the total system (they were very opposed to going through the floor). Second, they had to come out 2 more times to fix minor leaks (one in the attic) which required me to dump 100 gallons of water from the tank into the street each time; not to mention it's just frustrating.

Also, the gas line was not plugged after the main install, but they did come back the day after I pointed it out (think they just forgot). A minor mistake, but potential big problem if one of the kids would have turned on the gas valve hanging at the end of the pipe.

That being said, in all fairness, this was their first install and they were very up front about that and made up for it with a large crew of guys and other incentives. So overall, I'm still very satisfied with how the install went. I'm sure the next time around for them will go much smoother.

However, I figure others out there will be in a similar situation as more contractors do this for the first time so I wanted to post exactly how this went and what I would do different. I guess in the end I would say that paying a little extra for experienced installers would not be a bad idea (if that's an option).

Wednesday, August 6, 2008

Looking into options

So our water heater died and I had a few options:
  1. just replace it and wait another 20 years
  2. go tankless
  3. go solar
I have 1600 sq. ft. ,2 bath, house with a family of 4 kids. I needed something that would eventually work with 6 people a day taking showers and what not. the water heater I had was 40 gal with a 36,000 gal BTU burner. We would occasionally run out of hot water, but the kids are little and didn't really take regular showers and baths. As they get older, obviously that would change.

Just Replace it:

this option was the cheapest but I had concerns about the amount of gas it used, the fact that the water heater and furnace and stove shared the same gas pipe, and the size of it. It was wedged in a closet by my front door so I couldn't go bigger without relocating the water heater anyway. This is probably the biggest reason why I didn't go this route. to flat out replace it on the cheap I was looking at $1k if I did it myself (which I would have to learn how to do as I went along). Had a pro come out and he quoted me ~$2k to do it right. However, if I wanted a bigger water heater relocated in the garage, then we were talking ~$2500-$3k. If I went for one of those super efficiant 80+ water heaters I was looking at ~$4,500k.

Go Tankless:

I thought this was the way I would go. However when I looked into it there were some problems. First, the most efficiant tankless water heater is electric. However, for a growing family of 4, I would need something that took a lot of amps of electricity. My home service is 100amp, but an electric was going require me to go to 200amp. someday I would like to do that but not today. So electric is out which leaves me with gas.

Gas is less efficiant (80-88% is what my research seemed to indicate) and it takes A LOT of gas to flash heat 4gpm of water. Tankless water heaters are rated by how much water they can heat with a given flow. My shower I messured at 2 galons per min. I have 2 showers and a dishwasher. In the winter, it can get down to the low 40's for a daytime high. so I need to be able to heat water up about 60-70 degrees @ 4 galons per min. all the units I looked at were in the 180,000 BTU range; that's a lot of BTU, much more then what my regular water heater, furnace and stove would all take at the same time.

When I had the professional come out to price one out, it turned out to be about what I expected. I would have to put the tankless right off the side of my gas service with 3/4 pipe and run lines to it through the garage. This was already at ~$4,500 and there was the possibility that it would cost more if I had to get an earthquake valve and permits. Finally, there was a chance that it could cost me more per month as I had found post from people who had gone this route only to find out that because of the high BTU needed to flash the water they used more gas in the winter then previous to installing a tankless. When I did the math comparing say 1 hour of use flashing the water with a 180,000 BTU tankless vs. say 6 hours of gas use on a traditional water heater; this seemed to make some since to me.

Solar Water Heater

I initially did not think that I would go this route, but the more I looked into it the more I liked it. I was thinking that we wouldn't get hot water during the night with a system like this, but that turned out not to be true...

There are many different types of solar water heaters but they break out into 2 basic types: passive and active.

Passive solar water heaters have no pumps and heat water directly. some systems have tanks up on the roof (usually painted black). The positive is that there are few, if any moving parts. the negative is that since it uses water directly, that water can freeze in cold weather.

Active systems use pumps and some kind of radiator fluid (like glycol). the glycol, in this case, runs through pipes in the panels, heats up, and is pumped into an heat exchanger in a water heater. Active systems won't freeze, but they have more moving parts which could break.

Solar hot water systems seem to cost a lot more then traditional or tankless systems. The system I liked would cost a little over double what a tankless would. Needless to say, I had to go back through my PGE bills and try to figure out how much gas I used for hot water heating though out a year; then amortorize that over the next few years to see if this system would pay for itself (figuring about 5% increase in gas cost per year). Still that cost came out to paying itself off in 10 years (best case) and 17 year (worst case). I'll post that excel doc (once I can find it). All this being said, I kept having this naging feeling that Natural Gas prices would go up higher then 5% on average of the next 10 years (I guess time will tell), but if it goes up say an average of 8% year over year, this system could pay for itself in 8 years.

The solar water heating system I went with is from a company called Velux and the integrators were a local company called the Solar Connection . Actually we were told that we were the first house in america to get this system (they seem to be big in Europe). The down side was that the water heater died in early March and this new system wasn't available until April; we waited and heated a lot of water on our stove.

I chose them because I wanted freeze protection, I liked the look of their mostly flat panels, and the hot water heater comes with a built in electric tankless backup which didn't require a service upgrade to my house (this is your failsafe so that you always have hot water). Since this was the first install in the US, it was also the first install for the integrators so it could have gone smoother, but they did their best to take care of me and I appreciated that they took their time instead of rushing it; I was happy with the final result. they also installed a solar tube in our permanently dark, kitchen which I justified as an offset to the electricity which the glycol pump would use (@ 90 watts per hour when it's running).

There's been a few times I've second guessed myself about putting down so much money on hot water heating, but I think in the end it will pay for itself and increase the value of the house.