My brother in law John is now retired and living with us here in Mexico. He is handicapped, but marginally able to look after himself, with autism, cerebral palsy, strabismus, and a few other problems. His whole life pretty much revolves around his Ekornes lounge chair and his cable television.

Probably 80% of his electrical usage is the Television, a flat-screen Sharp about 10 years old, something around 32" diagonal measurement. Maybe 2% of the bill is for lighting, the remaining 18% his refrigerator. He spends at least 15 hours per day watching the television, and is quite content in his limited world.

However... Mexican electricity rates are preposterously low -- UNTIL you pass the low-rate thresholds. It is a three-tiered system, and when you reach the third tier, your rates are perhaps four to five times what they are at the basic rate. John's usage is about to put him in the third tier. You reach third tier, the DAC rate (Domestic Alto Consumo) when your consumption over the previous 12 months totals 3,000 KWh or more. As long as your previous 12 months are over that magic number, you pay the top rate for every KWh you use.

To put in in perspective, my electric bill (for two of us, myself and SWMBO) with two desktop computers (we have to have two because of our religious differences: SWMBO is Macintosh, I am Windows) amounts to about $12--$13 per month. John is headed towards a $70/month bill if we don't do something to cut back his consumption.

Rationing the TV hours is not an option. It is literally all he has.

Are newer TVs enough more efficient to make it cost-effective to replace his old one? Are there other options, like VR goggle TV sets or something?

Ideas?

tanstaafl.

What level of electrical consumption by the TV is necessary to achieve the desired utility billing status?

Can you work it out to some maximum number of watts per hour?

Is it possible to supplement the utility electrical supply with solar, or wind?

((3000 KWh * 0.8) / 365 days) / 18 hours = 365W

A quick Google suggest a 32 inch LED/LCD should be in the 70W range.

Unless his old flat screen is a plasma or CRT, it seems unlikely he is using the 365 watts your figures suggest.

Unless I got my sums wrong

When in doubt, get yourself a Kill-a-watt and do some power-usage auditing. That will either definitively blame the TV, and then you replace it, or it will point to other possibilities. (Power theft by a third-party? Billing errors? Wildly inefficiencies in places you don't expect like the lighting?)

Andys maths looks pretty right to me. A large plasma could easily be that much power but a 32" which basically has to be an LCD is unlikely to be anywhere near that.

MY first thought was a Kill-A-Watt type meter too.

And are you sure about those percentages? 2% for lighting seems unreasonable.

Water heater?

A back-lit LCD TV that pre-dates LED backlighting can easily consume 150W-250W. Ditching that in favour of a newer, LED-backlit model should reduce that figure to just over 1/10th.

-ml

My first thought would be to put some solar panels on the roof and simply product most of the electricity yourself. After all, this is Mexico and sun should be abundantly available I would think?

My mistake.. just over 1/5, not 1/10.

Pretty close, Andy. But it would be "... /15 hours" not 18. In any case, it's irrelevant, because I totally screwed up on one of my assumptions. When I ran my calculations, I completely forgot that the billing is bi-monthly, not monthly, so John is only using half the amount of electricity I was basing my projections on. Thus he is safely removed from the clutches of the dreaded DAC rate.

In a word, "No". At least, not as of four years ago when I prepared the attached Excel spreadsheet. The up-front costs at that time were prohibitive. To tie into the existing grid, a minimum of six panels is required in order to match the line voltage. In view of my original error (see above paragraph), even though it would reduce John's electric bill to less than seven dollars per month, it would still take more than 25 years to amortize the expense of the initial installation. Even if the cost of the panels has decreased significantly since the last time I checked, it would not be financially optimal.

I did that this morning. The TV set and the associated cable box and the cable company's provided surge protector come to 150 watts. John's total usage is 160 KWh per month, of which (by Andy's/my calculations) means the TV is accounting for about 70 KWh per month, far less than the top-of-my-head estimate of 80% of the total.

As Shonky pointed out, 2% estimate for lighting seems unreasonable. Well, I calculated (rather than guessed) based on the number of lights he has, their wattage, and his usage and the true value would be closer to 4%. Really. He sits in a dark apartment watching television 15 hours a day, he doesn't use much lighting.

That leaves the refrigerator as the only other significant power user. The Kill-A-Watt shows it is running at 125 watts. In order for it to use the remaining 80 KWh of the 160 KWh actually used during the month (after subtracting out the television, the lights, and another 5 KWh for Miscellaneous), that would suggest that the refrigerator is actually running 21 hours per day. I don't think that is the case, but I will plug the Kill-A-Watt back into it and let it run for six hours or so and see how many minutes per hour it actually does run. And, double and triple check that the incandescent light inside the refrigerator actually turns off when the door is closed! (The light itself doesn't use much... but the energy required to remove the heat generated by the light is, I suspect, substantial.)

My house is divided into four apartments, each with its own meter. I am beginning to suspect that the circuit allocations have one or more circuits going to John's meter from other apartments.

In any case, it isn't something to be as concerned about as I was originally. His electricity costs, assuming usage similar to the past two months, still only come to about $18 or $19 USD per month. He can afford that. But nonetheless I am curious about just where all that electricity he is paying for is going.

tanstaafl.

ps: If you are (like me) an Excel nerd, you may find the attached spreadsheet intriguing. A LOT of work went into it, and I received a good bit of help from Paul Grzelak who, while not an Excel expert is a quite competent programmer who could quickly put his finger on the things I did wrong that kept the spreadsheet from working as expected. Try it out, see what happens when you change the variables, and gain an appreciation for just how incredibly complicated the electric company's three-tiered billing structure actually is.

db

This is the one area where I'm using LED lights, it seems silly to have heaters in the fridge. Especially the wine cooler, that runs its light continuously.

Hmmm, if you want to pursue this, one method would be to run a temporary long extension cord from your apartment to his. Connect his TV gear and refrigerator.

Then make note of the electric meter reading and the time, then wait. See if his meter reading advances despite there being almost (or genuinely no) load inside the apartment.

You might have to monitor it for a while (overnight or a few days) if the pirate electrical load from some other apartment only occurs when that resident is home, or cooking, or whatever.

Or put everything onto the extension cord, then pull the meter or turn off the service panel for that meter. Then see what complaints arise from the other residents.

You might even discover it is your own apartment that is benefiting from his meter.

MYSTERY SOLVED

After leaving the Kill-A-Watt plugged in for six hours, I have used .80 KWh.

That works out to a constant 133 Watts. The Kill-A-Watt shows that the refrigerator is drawing 127 Watts while it is running, so I can't explain the extra six Watts. But it is apparent that the compressor on that refrigerator never stops, 24 hours a day, 168 hours a week, ~732 hours a month. Hmmm.... 732 hours * 127 watts comes to 93 KWh per month, more or less in the ballpark with the estimate of 80 KWh per month, or 85 KWh if I drop that "Miscellaneous" 5 KWh from the previous speculation.

I'll let the Kill-A-Watt run overnight and see if the numbers hold up over a longer time period.

It is an old, medium-size refrigerator purchased a year or so ago at a garage sale for about $100. It's costing us a little over seven dollars a month to run it, so I don't think it would be cost effective to replace it. Of course, how long the compressor will last running 24/7 is anybody's guess.

tanstaafl.

Exactly how old is this refrigerator?

Is it a frost free type or the more basic 'frosting' design? Does it have a freezer section as well as the fridge section?

I have no idea how old it is. If I had to guess, it is probably 20 years old.

It is a refrigerator/freezer, with the freezer portion on top, frost free. It seems to work well, other than never shutting off. It doesn't appear to be a thermostat problem -- the freezer and the refrigerator always stay at the desired temperatures.

We'll probably just keep running it until it quits, and then either take it down the street to the repair shop (probably would cost about $30 to put a new compressor in it) or give up and find another yard sale.

Or, perhaps it would make sense to be pre-emptive and take it to the repair shop before it quits...

tanstaafl.

There should be a sticker or plate on the thing somewhere with the model code, manufacture date, etc.

I am wondering if the defrost heater is working frequently or continuously, thereby creating a heat load for the compressor to struggle with. Or the control/timer thingamajig (TM) is done gone wrong.

Compressors tend to last almost forever. The control units and air circulation fans, not so much.

Sometimes the exposed coils on the back or bottom of the fridge just need to have the dust bunnies cleaned off, there may even be a (broken) fan if the coils are tucked underneath.

Lots of things can cause a fridge to run much more than it should, often these things can be ignored for years, you just keep paying for the electrocity.

I would also suggest giving the coils a good vacuuming and see if that helps. Those dust bunnies are insidious bastards.

Excellent idea. As soon as my lazy brother-in-law wakes up I will pull the back cover off (4 screws) and vacuum it out.

I found the manufacturer's sticker, the refrigerator was made in October of 2000. So about 16 years old now.

I have had the Kill-A-Watt hooked up now for 19.5 hours, 2.07 KWh consumed, giving an average load of 106 watts. Since the refrigerator draws 127 watts while running, this would suggest that sometime during those 19.5 hours the refrigerator did turn off, accumulating about 3.2 hours of down time.

Another thing that might be contributing to high usage is not solvable without some serious remodeling of the apartment. The refrigerator is tucked into a tight little nook, with no more than five centimeters clearance on sides and back, open on top. The manufacturer's sticker says this is allowable (minimum required clearance is 2.5 CM) but no doubt it would be happier in a more open environment.

tanstaafl.

Needless to say, a newer fridge might consume far less power. And we've discussed that a newer TV would similarly save on power. After that, it's basically light bulbs and (if you've got it) air conditioning and/or electric hot water heater.

Going from incandescent light bulbs to LED bulbs is a huge big deal. Not only do you save the primary power consumption, but you also save the AC necessary to remove all that heat. Plus sitting under incandescent or halogen bulbs can feel like your head is getting toasted.

Air conditioning, of course, is a massive power sink. In a place like Houston it's not optional. Fancier thermostats let you schedule the fan to run independent of when the AC runs. This was hugely helpful for our house.

Water heaters, like all things, age out and need occasional replacement. If you're looking at an older electric water heater, then you may wish to consider alternatives there as well.

Yes, but the TV and the refrigerator combined are costing me about twelve dollars a month to operate. Before I realized my mistake about the bi-monthly billing, I was seriously concerned about going into the third pricing tier (the DAC rate) which might have made replacing the power-hungry appliances more appealing. But as things stand now, DAC is not a problem.

The very few light bulbs in the apartment are all compact fluorescents. I'm guessing that total light-hours of all bulbs combined come to less than an hour a day. Hot water heater is propane, and at about $30 per month costs more than all other utility expenses (excluding Cable TV subscription) combined. Air conditioning is not needed--one of the four walls of the apartment is actually below ground level, and outdoor temperatures rarely exceed 85 degrees F.

My apartment, which is on the top floor of the building, has solar hot water heating which has proven highly effective. A couple weeks ago, on a day when the outside temperature was in the high eighties, I measured the temperature of the hot water in my kitchen at 170 degrees F.

However, in contrast to John's apartment, three of the four walls of my place are glass from floor to ceiling, and it is not uncommon for indoor temperatures to get into the 90's. So, we have A/C in our place. Because of all the glass, we don't try to cool the house. Instead, if it is just too warm, we lie on the bed, switch on the A/C for half an hour, and cool ourselves. We used the A/C very liberally in May and June, with the result that our electric bill was staggering -- $52.94 for the two month billing period, or something over twenty six dollars a month.

My thermostat is very fancy, it actually talks to me and when it gets too hot it says "Where's the remote for the air conditioner?" and moments later, like magic, the A/C comes on.

tanstaafl.

It wasn't too dusty inside, no dust bunnies to be found.

However... That big black dome-shaped thingamabob (sorry about the technical description) was really hot. I could touch it but could not hold my hand on it. Is that normal?

tanstaafl.

That is the compressor. Doing its job. But it shouldn't be running all the time. Googling says ~50% duty cycle, once the interior temp is down.

Looks pretty similar to the back of our fridge here. I imagine most probably look like that.

The sealed black compressor compartment contains the compressor motor/pump thingie, suspended by springs to help keep it quiet. Three springs, apparently.

On our fridge, two of the three springs have broken or become disconnected. The result is a rather loud BANG-Bang noice when it switches on or off. It's been doing that for about 8 years now, and at some point we expect the third spring to give way.. and a new fridge to replace it.

Cheers

Oh Doug, believe me, it can be much, much worse. Having prices like yours would actually make me smile. (I know this is not much help to you, but just to put this into perspective)

In Belgium, they have just announced the seventh (!) increase in the price of electricity in the last 18 months. A "normal" electrical bill for an average household (= 4000 to 5000 kWh/year) is now 200 euro/month easily. When I look at my electrical bill now, only about 1/3 of it is the actual cost of electricity, the rest is pure taxes.

It's for this reason two years ago I put photovoltaic panels on my roof, enough to produce my entire yearly need for electricity. So you would figure my total electrical cost would be 0 euro, right? Wrong of course! It was like that for the first year, but then our resourceful government changed the system with a draw of the pen and implemented a "grid power injection" tax on the inverter of my PV system: 75 euro/year/kVA (+ VAT). My inverter is a 10 kVA model, so that's 750 euro x 21% vat = 907 euro/year = 75 euro/month for electricity which I'm producing myself, and of which the government uses the surplus for free (in other words, I don't receive anything for the electricity I produce and don't consume myself).
How's that for fair?

Because of these 7 increases in the electricity prices/taxes, I'm now paying...about the same amount/month I was paying BEFORE I put that 20.000 euro installation on top of my roof. (of course, without it, I would be paying a lot more even). It's mind boggling!

When I planned the PV installation, I had calculated that in about 8 years time I would be break-even (because I wouldn't be paying any electricity anymore). Now, with these extra taxes, it will take me 17 years. And if I add to this the fact that an inverter normally lasts about 10 years before it will need to be replaced (cost : +/- 2200 euro - at this time) there's hardly any "free" electricity for me left, considering a normal PV installation lasts about 20 years. If they keep increasing or inventing new taxes like they've been doing for the last 18 months, I will never even reach break-even before my PV installation is at the end of its lifetime.

Governments... the most unreliable partners you can imagine.

In the UK you get paid for the power PV puts back into the grid. They do however keep scaling back the payment, but thankfully they don't apply it retrospectively to existing installations.

I looked at solar when we moved 3 years ago, but the figures just didn't make sense. Yes I would have got my money back after a few years, but none of the estimates you see listed include things like replacing failed inverters (or worse). Had we moved a few years earlier, when the subsidies were higher it would have made perfect sense.

Also it might still make sense if I had £10,000+ just sat around doing nothing, but when the choice comes down to deciding between spending money on fixing other parts of the house and solar, keeping the house standing wins. Though it occurs to me that maybe I should run the figures again, but taking the money out of our mortgage account where the interest rate is down at 1.25% (for now at least)

I never received any subsidies for my installation. They stopped handing them out in 2013 (after having scaled them back to almost nothing in the 4 years before that), so my only profit was my electricity meter running backwards. But even considering that, it was still worth it, because as said I would have broken even in 8 years.

But then the government started to realize they had been overly generous with their subsidies, to a point that they had created a pit of more than 10 billion euro. So they want that back now, and their way of doing that is increasing everybody's electricity bill, also the people who never owned any PV panels.

The really disgusting part is that the real culprits here were not the families who had put 20 PV panels onto their roof, but rather larger companies who had put thousands and thousands of panels onto the roofs of their malls, factories, silos and even plain in the fields onto special solar trackers. The government subsidies raked in more money than actually producing grain or something onto those fields.

So the companies won 3 times: they created a cost which they can deduct from their taxes (usually "green loans"), they get government subsidies for the produced power for at least 20 years and they get their own electricity for free. How's that for a hattrick?

As said, the contracts for the subsidies that were drawn up lasted for at least 20 years, so today they companies are still making enormous amounts of money on the back or the normal people who now see the price of their electricity go up as a result. And of course, for the normal people, all the measures were taken retrospectively to existing installations.

That's the cost of green energy for you. And they they wonder why I'm all for atomic energy. (well, the new Thorium Molten Salt Reactors (MSR) anyway)



Even without the subsidies, it WAS still worth it. But then they killed the market with their extra taxes. If you don't have these kinds of restraints in the UK, then I would say: go for it, you'll be very happy once you have them. But as said, they problem is you can't trust the government they won't change the rules of the game.

To save the market of the solar panels somewhat, they've now made the "ecological rules" to which you have to comply when building a new house SO strict, you're obliged to put PV panels onto your roof or otherwise you simply CANNOT comply and will be fined (a lot!) for it. (all in the spirit of a "greener environment" of course)
They call this the "EPB" system, which looks at a total number of factors of the construction (thickness of walls/roof, used materials, insulation factor, ventilation, type of heating, water supply, length of hot water tubing in the house etc) and distills all that into something they call an "EPB number". The lower this number is, the better the house is insulated (or more self-sustaining), but of course a lot more expensive to build. A house with an EPB number of 20 or less is considered to be a passive house. Five years ago, you could still have an EPB of 100 and get away with it, but they decreased that number every year. Now you need to have at least 50 or less or you'll be fined. You can never reach 50 simply by adding more insulation. You NEED something like a heat pump, PV panels or automatic ventilation (and possibly all three combined). This adds a LOT to the cost of a new house, even disregarding the fact that the cost of all the other, normal building materials have a least doubled in the last 10 years.
Because of this, building a house, even a small one, has become unpayable for young starters who don't get help from their parents. This was not the case up to ten years ago. It's sad really.

Replacing my 1994 era fridge with a new one scares me. It seems like the new fridges have all kinds of issues with circuit boards going out. In the last three weeks, two of the guys in the office have had problems with three fairly new (7 years old or so) fridges, one of them on the fourth repair call. The old fridges just work.


I thought my electrical bill sucked in the summers, being in Phoenix. I haven't hit $200 yet this year, but that is bound to change for June, the temperatures have been fairly warm. But 200 Euro/month all year is ridiculous.

Actually... I was being facetious. I know that my electric bills are preposterously low.

Back before I left Alaska, and before I changed the house over to a very efficient Buderus oil-filed furnace, my house was total electric (don't blame me, that's how it was when I bought it!) and in the worst of the winter months my electric bill could run six hundred to seven hundred dollars. It was a big house, much bigger than I needed, and I kept most of the rooms at 45 degrees F (7 deg. C) because I wasn't using them. Had I kept the whole house at a comfortable temperature I could easily have run up a $1500 monthly bill.

Note that the electric rates are "preposterously low" only if you stay in the first and second tiers of the pricing structure. Heavy users are penalized. My neighbor across the street with a big swimming pool and a casual attitude about leaving lights on runs up bills in excess of two hundred dollars a month, compared to my usual twelve or so dollars.

tanstaafl.

Each state in the U.S. has a different way of making it work. In Texas, we get the federal tax credit (basically, a 30% rebate on the cost of installing your solar system) and then? Not much. Up to recently, the best plan around charged $0.12/kWh with net-metering, so every joule you generated directly offset a joule you'd be consuming, but that's against normal retail prices more in the $0.08/kWh range, so I felt like I wasn't being treated very well.

More recently, I'm on a "beta" plan from a vendor who doesn't want their name in public yet until they work out the kinks. I'm paying roughly $0.07/kWh for downstream consumption and I'm reimbursed $0.03/kWh for my upstream production, with a $5.50/month service charge. I ran the numbers with my prior year's usage and came out $100 worse than my prior plan, so they gave me a $100 gift certificate. Umm, okay then. What I like about these numbers is that you're now incentivized to store your electricity rather than feeding it back, and you're also operating a bit closer to the bare metal of the way wholesale electricity is priced.

My complaint, such as it is, is that neither net metering nor my current asymmetric plan really capture the place where solar really, umm, shines, which is when you're in a very hot sunny day, the grid is at its limits, and they're trying to reduce consumption. Businesses who buy into cheaper tiers of electricity are then compelled to turn things off. If that's not enough, you get into rolling brownouts. This is precisely when you want to have the benefit of home solar systems. They produce peak electricity at exactly the time when the grid is most taxed. So here I am, selling joules back to the grid exactly when the grid most needs it. Am I getting a price premium? Nope. But maybe I should be. Of course, if that upstream number (currently $0.03/kWh) tracked the minute-by-minute wholesale electricity rate, it would often be below $0.01/kWh. At that point, the only way solar would ever be profitable is if you had a battery to store your excess production, and those aren't cheap right now.

How feasible would it to set up, your presumable hot water heater, to only run when there is an excess of solar energy, rather then all the time? Although this could leave you with cold water in the morning, maybe just restrict the lower element, so the upper can still heat a smaller amount of water.

In other word, without resorting to batteries and other means of storing energy, is there a way we can automatically consume the excess PV energy when it is available, rather then sell it to the grid at a low price, only to buy it back later for double.

I have my own selfish reasons for asking, there is a housing development going in the next town over, that we may buy into in two years time. The houses are HERS 55 rated (24" stud spacing, 6" insulation + R12 sheathing, triple glazing, etc), all electric, and PV ready. I expect at some point, that National Grid will push a similar plan to yours, so I'm curious what options exist to balance things short of battery, or a Tesla.

You can assemble more than one electric water heater into a storage group, or even better, heat the water with a rooftop solar water heating system. Store up the excess hot water in several tanks.

Keep going with that thinking and you end up with waster circulation heating of the building plus plenty of hot water for other uses.

Storing electricity looks to be on the cusp of becoming economical. Choose a house layout and wiring that can accommodate future battery wall packs (or whatever) and install them when the pricing matches your criteria.

Long term I think the grid will become the backup and the local electricity storage will become the primary.

What does PV ready mean in this case? Just some wiring, or a roof design with maximal southern slope exposure and structural mount points for the solar array frames?

Like this. It provides water hot enough that I have to be careful, and in sufficient quantity to serve two apartments.

Interestingly, even on a hot day when many things are uncomfortable to touch, those glass tubes transfer heat so effectively that they feel cold.

tanstaafl.

Precisely like that.

Those vacuum insulated tubes can provide hot water even in cold Canadian climate and on moderately overcast days.

If there was a cost effective way to convert excess thermal hot water into electricity, PV and batteries would not be needed.

Yeah, our first house here had a pool and the pump ran 3 hours a day, which coupled with our normal power usage, pushed our bill to $3500 pesos ($195). I'm looking forward to lower bills at our new place although I haven't gotten the bi-monthly bill yet.

Is that for one month, or is that the bi-monthly bill? My neighbor was $7,000 pesos plus on a bi-monthly basis.

tanstaafl.

Honestly I didn't ask, it was just the RE agent I was speaking to. But the impression I got was it was just the wiring. Looking at the overall development layout I didn't notice anything special being done for solar alignment.

How effective was the pump only running 3 hours a day? When I had my pool resurfaced a few years ago, they recommended an hour for every 10 degrees of water temperature.

We've got two 50-gallon natural gas water heaters (piped in series with one another -- which my plumber says is something they'd never do any more). In the summer, they account for the bulk of our gas bill, which will hover around $25/month. I'm looking to replace them with a new high-tech hybrid tank or a tankless, either of which would be radically more efficient. So storing excess electricity in hot water isn't particularly attractive.

What is attractive is over-air-conditioning the house. While the usual environmentally friendly thing to do is to run the AC less during the day when you're not home, then have it come up to speed when you're on your way home, I could instead keep the house cool all day, perhaps even cooler than I want it when I'm home, consuming a big chunk of my excess solar production. This is better for the house, in some regards (cooler air = drier air => less mildew/mold), but would put more wear on the AC compressor/motor.

If I were super high tech, I'd bury a cold water tank in the backyard and I'd store chilled water, for the AC to use whenever I needed it. Chilled water distribution is commonly used in commercial system, where they might chill water all night, when power is cheaper, and then use it all day. If I were building a house from scratch, I'd look into this. Needless to say, it doesn't appear to be an easy retrofit.

That's for two months, but we were living on the edge of DAC for several months and then in December with all the Christmas lights and tree, etc.. we went over and wow! the bill more than doubled for just a few more kwh than before.



I know next to nothing about maintaining pools, but it seemed to work great. We only had trouble twice in the year when the chemical balance got off a bit and it got a bit green until the pool guy came and fixed the chemical balance.

For the majority of people on this bbs (at a guess, I'd say all but the two of us!) there is no understanding of what DAC really means.

It doesn't mean that for that one month with the Christmas tree lights you paid a penalty. It means that for however long it takes, every subsequent bill will be at the DAC rate until the total usage over the 11 previous months plus the current month adds up to less than 3,000 KWh. This is made even more complicated by the bi-monthly billing, so that even if your total annual usage at the end of December totaled 3001 KWh, you couldn't get out of DAC until the end of February.

tanstaafl.