DIY Energy Audit, Part 2: Why Do Heat Pumps (sometimes) Cost a Fortune to Run?

After the first article, Matt collected his utility bills and other background information we need to get started. Here it is:

“Colonial 3,300 square feet. 3 adults one child. 2 Electric Heat Pumps: Large one in basement is Payne, Model Number PF1MNB048; Smaller one in mud room for rooms above garage has no name. Just has large number SA11694 and Model Number BCS2M18C00NA1P-1. Thermostat at 72 now and 70 in summer. Consumption Feb 2013 through Jan 2014 – kWh 5800, 4530, 2815, 1684, 1533, 2346, 1334, 1568, 1719, 3023, 5833, 7349”

I don’t even have to make a spreadsheet for this one!

What this tells us

We have a small-medium family in an average sized development home – no red-flags there.

However, the next items contain the keys to solving this mystery.

Continue reading

Bright Ideas for Saving Energy #3 – Light Bulbs Add Up

The pie chart shown here should look familiar by now. We’ve already talked at length about the big slices of the pie – heating and cooling. Now it’s time to move on to lighting, shown here as 12% of the typical household energy usage.

In my experience with real homes occupied by living, breathing families, that 12% number may considerably underestimate the actual energy consumed. I’m sure that I’m biased because in my area, there are lots of large homes with modern amenities like ceilings filled with recessed lighting.

Fortunately, this is one area where homeowners can easily assess their own energy use and take actions that immediately reduce their energy use.

I have a good friend who moved into a new house. After the first few months of living there, he was about ready to move out because his monthly electric bill was averaging around $750! Fortunately, being a good engineer, he quickly noticed that this house was well lit – very well lit! There were dozens of recessed lights on each floor of this home. And with two children active at home, most of these lights were on all waking hours.

At first, he would follow the family around, grumbling as he turned off light switches. But this was a losing battle. He simply could not keep up with this round the clock. It was frustrating to him and annoying to his family. What to do?

My friend decided to start changing light bulbs. Week by week, he replaced the high usage lights with high quality compact fluorescent bulbs, each using about one quarter of the energy of the original bulbs. Pretty soon he had a box of old 90w flood lights, replaced by 23w CFLs. He was happy knowing that the house was still well lit and safe for his family but every bulb saved 67w. He also was glad not to have to replace the bulbs as often because his home has high ceilings making changing bulbs inconvenient.

A few months later, my friend came to me with a big smile on his face. “Got my latest electric bill!” he said happily. I looked at him curiously, wondering why he would be so happy about an electric bill. “It was under $250” – he beamed. “Holy cow”, I said – “you knocked $500 off your electric bill?” “Yup – it was all those damned light bulbs. I still follow them and turn off the lights, but I don’t worry about it so much any more.”

While this was an extreme example, it is a real one. Light bulbs do make a difference – the more you have, the greater the potential savings.

I’m not going to argue about the pros and cons of compact fluorescent bulbs. There are more than enough sites that discuss mercury. Instead, I’m going to show you how much energy you can save and teach you how to prioritize bulb replacement.

Step 1: Monitor Your Usage

Spend a week just paying attention to how the lights are used in your home. Which lights are left on all day? Which to you tend to turn on and off frequently? Do you have outdoor “safety” lights that stay on all night? Are there lights where the “color” is particularly important (like above a dressing table)?

I highly recommend keeping a notebook where you log each area of the house, how many bulbs there are, the wattage of those bulbs, and the number of hours they are on each day. This will make your job even easier later one.

Step 2: Prioritize Your List

Once you’ve monitored your usage and created your list, find the area with the highest usage. The highest usage is defined by the number of bulbs times the wattage of the bulbs. For example, if you have two, 100 watt  flood lights on each of the four corners of your home and those lights are on from 8pm to 8am every day, that equals 100 watts times two bulbs times four corners times 12 hour. Arithmetically written: 100 x 8 x 12  = 9600 watt hours

If you’re not familiar with spreadsheets, this is the time to learn. Plug your list into a neat spreadsheet and you’ll be able to do all these calculations really easily and then automatically sort the list by watt-hour consumption figures.

Step 3: Replace Bulbs

Assuming that you want to keep the light output from the bulbs the same, find appropriate high efficiency replacement bulbs and start replacing lights! I highly recommend checking out the EFI Store. I’ve been buying most of my energy efficient lights, fixtures, etc. from them for years and they’re amazing. Their entire business is built around helping people save energy. And, they sell quality products unlike the “big-box” stores that sell a lot of poor quality items.

A Few Considerations

  • I mentioned earlier that there are some fixtures, like above a make-up table, where you might not want to change the bulb to a CFL because color quality is important. I don’t want to sound sexist, but there’s no way around it – if you have a place where you or your spouse puts on makeup or gets dressed, don’t use CFLs. Most modern CFLs don’t have the color quality needed for this critical need.
    However, some of the LED lamps, like the CREE units sold by EFI, do provide excellent light quality.
  • LED bulbs are expensive, there’s no way around that. However, in high use areas, they can pay for themselves in a few years. They also last forever (25,000-50,000 hours) so there’s a good chance that you’ll never have to replace them.
  • If you are going to replace a light controlled by a dimmer, make sure that the replacement bulb is “dimmer compatible” or “dimmable”
  • Do not use fluorescent bulbs in areas where they’ll be on for short periods. The life of a fluorescent bulb decreases the more often it is switched on and off. So a bulb rated for 5,000 hours of life might only last 2,000 hours if flipped on and off frequently. Fluorescent bulbs are best suited for those areas where they’re left on for hours at a time, such as living space lights or outdoor safety lighting.
  • Fluorescent bulbs take a long time to warm up in cold weather, making them inappropriate for outdoor lighting that must come on quickly. For example, if you have motion sensors, this is not an appropriate place for fluorescent lights. However, this is a good place for LED lights since they come on to full brightness immediately. On the other hand, I use 13w CFL bulbs in my outside post lights that I have on a timer to come on at sunset and turn off a few hours later. They’re perfect for this application.

How Much Can You Save?

Remember the spreadsheet I had you to make earlier? Well, now’s the time to look at it more carefully.

The example of outdoor lighting I walked through showed that those outdoor bulbs use 9,600 watt-hours per day. Divide that by 1,000 to get the kilo-watt hours of use per day. In this case, 9.6. Electricity is sold by kWh, so this lets you easily compute the cost.

You’ll want to look at the rating of the bulb you buy to replace the inefficient one and do the calculations again. For example, if you replaced those outdoor lights with 23 watt CFL bulbs, the calculation is: 23 x 8 x 12 = 2,208.

Now, subtract this from the original to get the daily savings: 9,600 – 2,208 = 7,392 or 7.392 kWh per day.

Let’s calculate the yearly savings. Multiply the savings by 365: 7.392 * 365 = 2,698 kWh

And, determine your real electric cost per kWh. Do this by looking at your total electric bill and dividing the cost by the total kWh on the bill. This will include all charges for generation, transmission, taxes, etc. and will give you a rough true cost of electricity. For example, if your utility bill was $200 and you used 1,500 kWh, your cost per kWh is: $200/1,500 kWh = $0.133/kWh.

Finally, multiply these numbers together to get the yearly savings: 2,698 * $0.133 = $360.

So there’s a complete and realistic example – replacing eight 100w bulbs that are on for twelve hours a day can save $360 per year, assuming you’re paying 13 cents per kilowatt hour. This is pretty typical. Add up your savings for all your fixtures and you can see how significant the savings can be.


Where to buy your bulbs:

As noted throughout this post, is the place I buy my high efficiency lights. Yes, if you click through these links, I’m part of their affiliate program, so I profit from your purchases. But that’s not why I recommend them. I recommend them because they’ve devoted their lives to helping consumers live more efficiently. They’re not some Johnny-come-lately store that’s just doing it because it’s the latest trend. Check out their blog and “about” pages and you’ll see. They deserve our support.

5 Bright Ideas for Saving Energy – #1 – Know thy use

When I give talks or do energy audits, people want to know the “best” ideas for saving energy. You know – the things that cut your energy bills in half and don’t cost much to implement.

Interestingly, this isn’t as crazy as it sounds. I’ve based my career on trying to give out as much practical information as possible. The theory is, if it’s easy and you can afford to do it, you’re much more likely to actually improve your home. This is as opposed to the idealist’s approach which promotes only doing things if you’re going to do them perfectly.

Without boring your further, let’s dive into five things that you can do to save energy in a meaningful way.

1: Know how to read your utility bill

By far the most important step to take is to learn how you and your home are using energy. This lets you prioritize your energy saving measures in a way that is most meaningful. I’ve seen people spend weeks caulking ares of their home that make absolutely no difference while leaving huge problems untouched.

I always recommend getting an energy audit as a starting point. However, the purpose of this article is not to get you to buy energy audits, it’s to teach you how you can do things yourself, so I’m going to skip that method.

The first thing is to look at your own utility bill. I can show you spreadsheets showing how other homes act, but there’s nothing like looking at your own utility bill.

Almost every electric bill has a graph like this one, showing a year or 13 months of usage data.

The vertical axis shows how much energy is used each month. In this case, it’s scaled from 0 to 2700 kilo-watt hours, or kWh.

Definition: a kWh is the amount of energy used by ten, 100 watt light bulbs in one hour.  This is the same as one, 1000 watt heating pad. If it adds up to 1000 watts and it runs for one hour, it uses 1 kWh per hour.

I hope that’s clear, because everything about electricity consumption depends upon you understanding what a kWh is.

On the horizontal axis is months. In this case, it runs from September of 2008 to September of 2009. This lets you compare this year’s bill for September with last year’s bill. This is very handy since it shows you at a glance if anything has changed dramatically since last year.

What does this graph tell us?

Look at the pattern of usage. The graph shows similar electrical consumption during September, October, May, June and August. Each of these has a total usage of about 450 kWh for the month or about 15 kWh per day. I’d include July, but that actually shows a bit less consumption. Maybe the homeowner went on vacation for a week in July?

What do these months have in common? The answer is – you don’t heat your house in these months. Now, look at the heating months. (Side note: this is from a home in Eastern Pennsylvania. This is a very typical heating consumption curve.)

The graph shows electric usage increasing in November, December, peaking in January, then dropping in February, March, and April. This makes sense too since January is consistently cold, so you’d expect the most usage when it’s cold. So everything makes sense.

Take a step back. What does this graph say about the house? It says that the occupant is using electric heating in an amount that is related to the outdoor temperature.

I’ll tell you a secret – this house is heated with oil, so somehow, the owner was paying a double heating bill, once for electric and once for oil. So just looking at the electric bill tells me that there’s something very wrong with this home. After all, if the home is heated with oil, why are they paying for an extra 2,000 kWh in January? That’s $320 in added electric costs (in this area). Over the course of the entire winter, they’re using 5,200 kWh, or about $830!

Winter usage spikes usually means electric heating

We’re learning an awful lot by looking at one part of an electric bill. Without even looking at the house, you know that there’s something happening here that’s dramatically increasing their electric bills in the winter. Common sense shows us that the usage corresponds to winter temperatures so it’s extremely likely that they’re using electric space heaters somewhere in their home.

It’s also telling us that they don’t use air conditioning during the summer. If they did, the graph would jump up during July and August, which can be pretty hot and humid in these parts.

Baseline electrical usage

Go back to our earlier observation that most of the non-heating months show an electric consumption of 450 kWh per month. The average usage during the low-usage months corresponds to the baseline electrical usage. This is the amount used for things excluding seasonal loads like heating and air conditioning.

For most homes, the baseline electrical usage includes electricity used for televisions/electronics, electric lighting, clothes washers/dryers, computers, dishwashers, electric water heaters, etc. – things you use all year long.

In this particular case, they use 450 kWh per month, or 15 kWh per day. This is comparatively low. Most homes I measure have 25-50 kWh per day consumption as the baseline, so the graph also tells us that there is nothing that is excessively sucking down electricity in the home during the non-heating months.

Getting More Specific

We’ve spent a lot of time looking at the broad usage patterns. What about specific consumption? Suppose we saw something that caught our eye on the graph, like high baseline usage? What then?

Recall in the definition of kWh I wrote: “a kWh is the amount of energy used by ten, 100 watt light bulbs in one hour.” I defined it that way because it frames an abstract term “kilowatt-hour” in a way that anybody can wrap their brain around. Ten 100 watt lightbulbs burning for one hour. Easy!

So, a home that uses 15 kWh in a day is using as much as those ten lightbulbs would burn during the waking hours. That’s not bad considering it includes all the washing, drying, dishes, television, etc.

On the other hand, if you found that the home had a baseline of 45 kWh, that would be like 30 bulbs burning all day – ouch! In fact, when I see a high baseline electrical usage, one of the first things that I’ll do will be to walk around the house, basically counting lightbulbs.

Obvious Problems

Quite often, these homes will be newer ones filled with recessed lights in the kitchen, living and family rooms. I’ll point at the kitchen ceiling, filled with 15 brightly burning flood lights and ask – “how long are these on during a typical day?” The answer is usually “oh, we keep those on from the time we wake up until we all go to sleep.”

At this point, my face will usually show disapproval (I’m really bad at hiding my emotions!) and I will say something like “do you know that those 15 lights, each 90 watts, are consuming about 20 kWh per day? That’s more than the ENTIRE household consumption of many homes?”

Anyway, I digress. The point should be well taken. Sometimes, the cause of your high consumption is blindingly obvious!

Not-so Obvious Problems

That was an easy (but very common) problem. What about the harder ones?

Well, sometimes, you just have to measure things, using a kill-a-watt meter like the one shown at the top of this post. This is a simple to use electric meter that any homeowner can use to measure the load of things that you plug in. For example, if you want to learn how much electricity that old fridge in the garage is using, just plug it in for a day and you’ll get a very accurate measurement.

Side note: occasionally, I’ll post links like this to items in the Ted’s Tips Amazon store. I’ve put together this store to hold all the items that I refer to on this blog so that you’ll be able to find them in one convenient place. Originally, I was linking to a lot of different sites, but then people would ask me where they could purchase them. Since I’ve been an Amazon user for years and know them to be extremely reliable and have low costs, I figured it was easiest to go this route. Anything you purchase there helps support this site. Thanks!

Back to measurements…

What Things Should You Measure?

You could spend months measuring everything in your house, but I’ll tell you where to start. These are the biggies. The proverbial “energy hogs.”

  • Refrigerators, especially old ones or those in garages during the summer
  • Dehumidifiers, especially those in damp basements or crawlspaces
  • Space heaters
  • Frequently used Halogen lamps
  • Anything with a heater in it that gets used a lot
  • Entertainment centers (especially large screen TV’s)
  • Large stereo amplifiers that get used many hours a day
  • Large gaming computer rigs

You should also make note of the following light fixtures. Keep track of the wattage of the bulbs and the length of time they burn each day.

  • Outdoor lights, especially bright flood-lights
  • Common area lights that are on most of the time (kitchen, living/family room, hallways)

I’m going to stop here for the day. This is more than enough to get you started doing your own home electrical consumption audit. If you follow these suggestions, learn how to read your utility bills and figure out how much energy you’re using, you’re well on your way to lowering your electric bill, maybe substantially. So get cracking – the watts are-a-wasting.