Almost everybody gets thrown off by this, but I moderate comments to avoid spammers. The downside of this is that you won’t see your comments post until I’ve had a chance to review and approve them. Sometimes this can take days (sorry!) Thanks for your patience.
As a baseline, consider that typical homes in the United States consume on average 30–60 kilo-Watt-hours (kWh) of electricity per day (=900–1800 kWh per month) at a cost of $0.10-$0.20 per kWh. Those running on electric heat often double these numbers.
- In homes with electric heat, the heater can dominate all other electric consumers. Heat pumps, while considerably more efficient (1/3 – 1/2 the consumption) than straight electric resistance heat (like an electric baseboard heater) still consume substantial amounts of electricity. Consider that a typical heat pump system uses 3kW – 6kW while running, daily consumption in cold days can easily be 30–60kWh or more. This is why home insulation and air-tightness is such an important way of conserving energy. Same is true if the home is heated with oil, gas or propane – home heating and cooling costs dominate all others, so a tight, well insulated home pays dividends year after year.
- Electric water heater – consumption varies drastically depending on a family size and hot-water usage. But an average is about 400 kWh per month. A modern heat-pump water heater can cut this in half.
- Refrigerator/freezer – older units were much less efficient than a modern, EnergyStar unit. A typical range is 40–80 kWh/month.
- Lighting – with the advent of energy efficient LED lights, this has shifted considerably. A home that has the equivalent of ten, 100W bulbs running 12 hours/day uses 12kWh per day or 360kWh/month. If all those bulbs were replaced by 14W LED bulbs that put out the same amount of light, that would be reduced to 1.7kWh/day or 50kWh/month. Lighting is an area where every home can dramatically reduce consumption by replacing conventional bulbs with LED in high use locations like the kitchen and living rooms.
- Air conditioner – central air conditioners and their blowers consume from 3–7 kilo-Watt-hours (kWh) per hour of operation.
- Home electronics – computers, DVRs, TV, stereos all add to a home’s use and together add up to 200W-1000W/hour, every hour. Typical consumption is 4–10kWh/day or 120–300kWh/month.
- Cooking – electric ranges and ovens consume 2kW–4kW while running and might be operated for an hour or two per day on average.
Other items that add considerably to electric bills but are less common:
- Pool pumps – most are drastically oversized and run 12 hours a day. A typical pump uses 2500W, so that’s 30kWh/day or 900 kWh/month! Replacing that with a two-speed or variable speed pump can cut this by 75% – well worth the investment.
- Spas/Hot tubs – outdoor hot tubs use about 6–15kWh/day, depending on usage, design and temperature, call it 10kWh on average. That’s 300kWh/month. Since many people don’t use their tubs during the winter, it pays to shut it down for the winter, saving about $50/month.
- Ponds – ponds have become very popular in the suburbs but most people don’t realize how much they cost to run. Those waterfalls require larger pumps, consuming 500W–1000W while a basic pond filter pump might use 100W-250W. Consider an average of 500W for 24 hours is 12kWh per day or 360kWh/month.
It’s extremely educational to install a whole-house energy monitor or use an inexpensive plug-in energy monitor to see how much energy each of your devices consume. But watch out, once you do, you may turn into a true energy geek, like me 🙂
I recently received this question on Quora and decided to share the answer with readers there as well as on TedsTips. I hope this will save some of you from heartbreak after your winter vacation!
A primary consideration in cold climates is pipes freezing. It is very important to realize that pipes can freeze even if the home temperature is above freezing due to the locations of the pipes. I once owned a townhouse where the pipes would freeze when the outside temperatures dipped into the single digits outside, even though we were warm inside the house. How? The pipes ran up through an inside wall, across the ceiling and over to an outside wall spigot. The inside wall, at the top, opened to the cold attic, so that cold air would get into the wall cavity and freeze the pipes. This was fixed by air sealing the top of that wall cavity, but required considerable detective work to figure out. The pipes running through the outer wall down to the spigot would freeze near the spigot where the pipes were exposed to cold temperature, so this run had to be isolated from the rest of the house plumbing and drained during the winter.
These are two examples, that show potential issues that are made worse by turning down the temperature while you are away. Imagine the situation where the pipes don’t freeze when the house is occupied and the walls are warm enough to keep the pipes from freezing. Now, imagine reducing the indoor temperature, maybe only a few degrees, but enough that the cold from the outside overwhelms the meager heat coming from the house that is able to reach the pipes. This has bitten many a homeowner during winter absences.
Unfortunately, there is really no way of knowing if this will happen until it happens. This is why it is critical that you turn off the main water valve for the water supply to your spigots in your house when you travel*. The pipes may still burst, but at least your house won’t flood. When you return after winter and turn the water back on, you’ll know quickly that there’s a leak and can turn off the water and fix the leak before catastrophic damage is done. This is no exaggeration – I was called into a home that was literally FILLED with mold and had to be gutted. A pipe had burst and the owner returned after a month to find the house completely flooded.
*I was reminded (see comment below article) that you MUST NOT turn off the make-up water supply if you have a boiler for heating your home. This is very important. Boilers need available water to maintain system pressure in your radiators etc. Without make-up water, the pressure in the system can drop and the system will stop functioning.
If you plan on leaving your home for an extended period, it is always a good idea to have your HVAC company give the heating system a once-over to ensure that it is in good working order. While there, they can advise you on which water valve you can safely turn off and which you should not touch. It would be advisable to label all the valves for future reference.
Flooding is the most damaging effect, but there’s another, more insidious issue that can arise during winter house shutdowns – condensation damage and mold.
In order to understand this, I have to touch on the physics of condensation. Condensation is the conversion of water vapor to liquid water that occurs at or below what is called the “dew point.” At normal temperatures (say 70F), condensation rarely occurs during the winter because the home humidity level is modest and most of the inside of the home is above the dew point. However, even with typical indoor humidity levels, you can experience condensation on windows, because windows get much colder than the insulated walls of the house. You might have noticed this if you have curtains or insulating blinds. These help keep your room warmer but allow the windows to get even colder because they intentionally reduce the windows sapping heat from the room. When you open the curtains, you might find the windows soaking wet from all the condensation. Worse, the wood around the window, especially at the bottom edge, might be saturated with water.
Under normal circumstances, you would see this in the morning and could dry off the wood and allow it to warm up when you open the curtains. But when you are away, even if you don’t turn down the thermostat, the water will remain and can get worse every day. Over time, this will likely lead to mold growth and if allowed long enough will rot out the wood. For this reason, I highly recommend that people leave their curtains and insulating shades “UP” or “OPEN” when they are away for extended periods. You want to minimize the chance of condensation buildup and the associated potential for mold and wood rot.
Let’s continue this thought experiment. If you turn down the thermostat enough, the inner surfaces of your house (walls etc.) can get to a temperature below the dew point and, just like those windows, the water vapor in the air can condense on those surfaces. Many people have made this mistake and come home to a horrible, moldy mess! For this reason, it is extremely important to do two things:
1 – do not turn down the heat excessively. It’s impossible to tell exactly what temperature is too low, but in most climates, people find 55F-60F is safest.
2 – make sure you don’t add any moisture to the air while you are gone. This can be disastrous. For example, many homes have central humidifiers built right into the heaters. If you leave this one it raises the humidity level inside the house every time the furnace runs, likely leading to moisture problems. Turn off all humidifiers before you leave!
Even if you don’t have humidifiers, natural ground moisture can seep into the house through the basement, crawlspaces, etc. This is especially common in homes with dirt floors underneath. Water vapor rises up into the house, driving up the humidity. If you live in such a home, it is really important that you monitor the humidity levels in the home to ensure that they are not too high. During winter, indoor humidity levels will naturally be low, typically less than 50% relative humidity. Humidity levels above 70% are considered too high as they promote mold growth. Get yourself a humidity monitor (they’re cheap on Amazon) and see what humidity levels are. Or better yet, get an Internet smart thermostat.
These let you to monitor indoor temperature and humidity levels while you are gone. These are affordable nowadays, and can give you tremendous peace of mind. A quick daily check on temperature and humidity gives you a read on the health of your home. It’s not a guarantee, as you still might have condensation problems, but at least you can be sure that the general climate inside your home is reasonable. It will also tell you that your heating system is working. If the temperature suddenly drops to 45 even though your thermostat is set to 55, you know there’s a problem and can call in help.
Have a wonderful winter. Hopefully you will avoid the main pitfalls that have hit too many other people. A few easy steps can greatly improve your odds of coming back to a healthy home!
A reader, Adam, recently asked about the pros and cons of using LED retrofits vs. sealing recessed lights from the attic. It’s such a good question that I had to write up a quick post detailing my thoughts on this important topic.
I’ll start by saying that I have upgraded all of the recessed lights in my home with LED retrofits. This has numerous benefits over attic sealing. Prior to good LED retrofits being available, I had constructed airtight/fireproof boxes installed from the attic, so I can comment on both methods from first-hand experience.
The retrofits were easy to do, taking maybe 10 minutes each, at most. These days, high quality retrofits are inexpensive, typically less than $30.
- Totally air-tight when installed properly with a good gasket
- Energy efficient – depending on your electric cost, the light will pay for itself, especially if it’s in a high-use location, like the kitchen. Usually less than a year.
- Energy efficient part 2 – you can insulate the attic properly above the fixtures. LEDs generate much less heat than incandescents. Plus, you won’t lose the heat from air escaping through the housing.
- Long lasting – quality LEDs are rated to last about 2-4 years running continuously. Compare this with an incandescent which has a life only one-tenth as long. This is much more convenient (less time on the ladder is safer too!). For most uses, that means you’ll never have to replace a bulb.
- The light quality of “good” LEDs is very natural if you buy high CRI (color rendering index) fixtures. This is very personal, so compare the light from different fixtures to find one you really like. I brought home several, installed them and then my wife and I could see how they looked in our own homes which is much different than the display case in the store. You can usually return the ones you don’t like, so it’s worth trying a few.
- The retrofit itself is quite simple usually. Most wire into your existing fixture using a screw in connector that replaces the existing bulb.
- Air/moisture leakage through recessed lights are one of the primary sources for mold and rotten roofs. By installing air-tight LED fixtures, you will potentially prevent a very expensive roof replacement and mold remediation.
Challenges with retrofitting from the attic:
- Working in attics is not fun. It’s hot, dusty and access is often difficult. This makes contractors less likely to do a good job because they’ll be anxious to work quickly and get out of there.
- It can be difficult to mount the air-tight enclosure in the attic given the construction of a typical recessed light fixture. This often leads to compromises that leave gaps, defeating the purpose of an air-tight enclosure.
- Incandescent lights generate a lot of heat. Some older fixtures aren’t rated for enclosure. Usually this isn’t a problem however.
- Covering the fixture with a housing can make insulation challenging. Most contractors are afraid of insulating around fixtures, leading to compromised insulation.
- Some LED lights are not-dimmable – so make sure to buy the right type if you need them to dim.
- The convenience factor of not having to replace bulbs in high ceilings is worth a lot.
- Make sure the chosen fixture is the right size (4″, 5″ or 6″) for your retrofit. There are also different mounting styles that can affect compatibility.
- Avoid off brands or those without a good warranty. The only trouble I’ve had with LED bulbs/retrofits are with cheap “knock-off” type. My favorites have been manufactured by CREE, which were the pioneers in LED lighting. Phillips also makes quality products.
- You still have to be careful in sealing the retrofits in order to make them air-tight. They need to have a good gasket and be firmly seated to the ceiling.
- The thermal image, below, shows a huge amount of air leakage around a so-called air-tight recessed light fixture. As with all things in home construction, installation is key!
- For best air-sealing, I have used foil-tape to seal the holes inside the existing fixture. Some people claim you need air flow through the fixture for cooling but the fact that these fixtures are built to be air-tight negates this argument.
In short – probably not. Unless it’s a Chevy Volt. Why? Read on! (Update, Sept 12, 2017 – Honda announced their new Clarity plug-in which sounds like it will give the Chevy Volt a run for its money! Update, Sept 14: Maybe not. Driveability sounds so-so and based on this article, you only get 121hp in EV mode 😦 ).
Virtually every auto manufacturer has pledged to electrify their product lines before 2025. This could mean making all their cars hybrids, like the Prius. But many are mentioning at least some of those cars will be “plug-in” hybrids or fully electric vehicles.
In previous posts, I’ve discussed the great benefits of pure electric vehicles – great drivability, simplicity of drivetrain for minimal maintenance, zero exhaust pollution, and never having to go to the gas station. I’ve also written about the difference between the types of electrified vehicles, but I haven’t done a deep-dive into plug-in hybrids. In all likelihood, you’ll be seeing many vehicles with this label in dealer showrooms, but what exactly do they mean? Hopefully, by the time you finish reading this post, you’ll understand and be able to purchase your next vehicle, confidently knowing exactly what you’re getting.
Plug-in hybrids are hybrid vehicles with larger batteries and a switch that allows you to change them from gas-electric propulsion to electric only. “Great!” you might think – “best of both worlds! Now I don’t have to worry about the range of the batteries since I can always switch on the gas engine.” However, all is not so rosy. As with everything in life, there are compromises. Continue reading
There’s been a lot of talk and press coverage about electric vehicles the last few years. Tesla, Elon Musk’s electric car company, has generated huge excitement with it’s sexy, high performance cars, but their price has put them out of reach of most consumers. The Tesla Model 3, to be released in mid-late 2017, hopes to change that however, giving you a 200+ mile range electric car for under $40,000.
Tesla isn’t the only game in town. Chevrolet released their sub-$40k Chevy Bolt at the beginning of 2017, and this compact SUV shaped electric vehicle has won accolades from all the automotive press, setting the standard for high range (200+ miles on a charge) vehicles.
These two are just the start of a flood of EV’s hitting the market. Virtually every auto manufacturer has promised a variety of electric vehicles – great news for consumers, but also potentially confusing.
In this article, I hope to arm you with some useful information so you can decide if an electric vehicle is right for you. Continue reading
Intuitively, clean solar panels are more efficient than dirty ones. But how much of a difference does it really make?
Like you, for years I have read that you *must* clean your panels because dirty panels waste so much sunlight. Since you’ve paid lots of money for your panels, you want every Watt that they can produce. But how much of a difference does it make?
This spring, after the flowers and trees sprayed their pollen everywhere, my panels were really dirty, totally covered with yellow pollen. I figured, this must be costing me big in solar production. So, being an energy geek, I decided to measure the output before and after cleaning (on consecutive days with clear skies at the same time).
In short, I discovered that, even this dirty, there was very little measurable difference. With my big array, when dirty, I got 8.4 kWh at the noon hour. After cleaning, around 8.5 kWh. However, the effect was so small that I think this measurement is within the margin for error since even a little change in conditions would make a greater difference.
Given the time and potential danger of climbing on the roof, hosing down the panels and cleaning them properly, this tiny difference hardly seems worth the effort. Certainly, it isn’t worth the several hundred dollars that a professional cleaners would charge, especially considering that the panels will just get dirty again after another week!
There are conditions when you should clean your panels. If you have a flat or very low slope roof in a dry climate, the dust can form a very thick layer that isn’t washed away by infrequent rains. Over time, the dirt will cake on, making it harder and harder to clean. Periodic maintenance makes sense in this case.
Bonus information – what really makes a difference in solar production!
As part of this experiment, I discovered that my solar panels were producing far less energy than expected. In the past, I had measured over 9.5 kWh for the noon hour. At other times, they produced less than 8.3 kWh. This is a *huge* variation! But why?
After some research, I learned that solar production decreases when the panels get hot. So I went back through years of solar production records from my system, picked days that had full, uninterrupted production (no clouds) and graphed it. Here’s the results:
First, I must explain why there are two lines. The bottom level, ranging from a max of 8.4 kWh to 7.4 kWh are the data from before my solar system was expanded. The top line is from after additional panels were installed.
Next, I admit that these are crude measurements because they are based upon the daily average temperature at my location. Ideally, I would put a temperature sensor on a panel, so I could measure output vs. panel temperature. However, the effect is nonetheless very strong and paints a clear picture – solar energy production drops very significantly as the days get hotter.
If you are paying attention, you will think – “when the days are colder, isn’t that winter, when the sun is much lower?” The answer is “YES!” My data were chosen between mid-March and mid-August of several years. You would think the June numbers, when the sun is highest in the sky would produce the most energy. Not so! Temperature clearly makes a much bigger difference than this amount of solar angle change. In fact, the best noontime production was in mid April, where the temperature is low and the sun is bright.
Please note that this is the peak hour production. The total day’s production, for my fixed mount system, is when the days are longest, even though the temperatures are higher. But I think it is useful for others to understand how much of a difference heating makes to solar production. So if you see your system underproducing during a hot summer day, that doesn’t mean it is malfunctioning. This can save you the pain and frustration of a service call.
The important thing that this implies is that a ground mounted system, with open backs and plenty of air flow as well as the naturally cooler temperatures of the moist ground below it, may be better for production than roof mounted, with very little natural air flow and a hot roof. Someone needs to study this, given how large a difference temperature makes to production.