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 had an interesting question – a reader asked what could cause a Fujitsu mini-split air conditioner to cause the air to become *more* humid. In fact, they noted that the air became highly moisture laden and the house was just yucky humid.
I really scratched my head on this one because, from a physics standpoint, under “normal” conditions, this is impossible with a mini-split. Why? Because a mini-split system has an air handler unit in the house with the only connection to the outside (and outdoor humidity) is through a small hole in the wall where the electrical and refrigerant lines run. And yet it happened.
The questioner noted that multiple units were involved and that various parts of the electronics had been changed, and yet the problem persisted. He noted that he’d heard of a number of other people with the same problem. I admit, I was baffled!
Then it came to me. In fact, I had worked with an associate, helping them to track down this exact problem. While I can’t state with 100% certainty that the problems were the same, the symptoms are the same. In addition, I realized that my own home’s systems exhibited the same issues, but I automatically made the adjustments to make the systems work properly!
One of the toughest things about researching a new heating system is learning the tech talk. Your HVAC company will throw out all sorts of terminology assuming that you understand what they’re talking about. Some might even be happy that you *don’t* understand so they can confuse you and sound like experts. Well, no more!
This post covers the most common terms that you’re likely to run across. I’m sure I’ll miss some or confuse you, so please post questions if there’s anything you’d like clarified.
In July 2014, I purchased this GE GeoSpring heat pump water heater to replace my existing all-electric water that had sprung a leak. Admittdely, it was an impulse buy because Lowes was having a sale on them – probably to get rid of unwanted inventory because these have horrible reviews!
So why did I buy it? Because it was only a few hundred dollars more than a conventional electric water heater and I’d been wanting to get an integrated HPWH after my previous add-on HPWH died after just a year. Plus, based on the negative reviews, I felt that the people having problems were using earlier versions of the heater. So I’m crossing my fingers and hoping that it has a long, happy life.
Almost everything written in this article applies to all heat-pump water heaters. I’ll put the GE specific notes at the end.
What is a heat-pump water heater?
You may not know it but your refrigerator and air conditioner are examples of heat pumps. Through a process of compression, condensation and evaporation, they move heat from one place to another. In your refrigerator, that humming you hear when it runs is the compressor. The inside of the fridge is cold because the “heat” in the fridge is moved to the outside of the insulated box and blown into your kitchen. An air conditioner works exactly the same way – it cools the air inside the house and expels the heat outside.
The HPWH does the same thing except it uses the heat to warm the water in the tank. And the cold? If you feel the output behind the heater, you’ll see that the cold gets blown into the room. Heat the water, chill the room. Keep this in mind, we’ll come back to that later.
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.
#1: Research replacement systems before your current system dies
Hopefully, you’re reading this before you need to replace your heating system. Other than buying a car, a new heating system is likely to be the biggest single item you’ll purchase for your home. And just like a car, you want to do your research before plunking down the the ten grand on something you’ll be living with for years.
Unfortunately, most people wait until their heating system dies – usually in the dead of winter. What ensues is an emergency phone-call to your “heating guy” who will either replace your system with exactly the same, inefficient, old unit you already have or whatever he’s got on the truck, most likely the latter.
You wouldn’t buy a car this way, would you? You wouldn’t call your car dealership and say “my car broke down, sell me what you’ve got. Maybe give me a few options for different cars.”
Heat pumps are a bit of magic. But you use one in your home every day – your refrigerator. So if you can accept that your fridge works, somehow making 0 degree air from the 70 degree air in your home, plus some compressor action, then you should be able to accept that heat pumps can produce 95 degree air to heat your home while it’s 25 degrees outside.
I’m not going to subject you to a full lesson on thermodynamics and the refrigeration cycle. Instead, I just want you to accept the fact that heat pumps work on the same principles as refrigerators and air conditioners – they move energy from one place to another. In the process, they make one side of the system hotter and the other side colder.
Heat pumps, refrigerators and air conditioners all work the same way – they move heat from one place to another, amplifying the effect using a compressor and refrigerants.