When you’ve got a home solar system and a current and/or future electric car you’ll be powering with that system, you start to look for ways to squeeze out every extra kWh hour you can for the electric car.
Where do you look first for electricity savings?
Central air conditioning. Even the most energy efficient central AC units suck down an average of between three and five kWh of electricity per hour. So turn it up a few degrees, use it less, or, if you’re a true energy miser and you live in a place where you can survive it (like Denver), essentially never turn it on.
Where do go next for electricity savings?
You might want to take a close look at your clothes dryer — and your clothes drying practices.
Our Whirlpool Quiet Dry dryer uses about five kWh of electricity per hour. That’s 55 cents worth of electricity for us (Xcel Energy charges 11 cents per kWh). But it’s $3 worth of gasoline replacement (assuming 20 m.p.g. and one kWh = four EV miles). In other words, those five kWh are $2.45 more valuable as a gasoline replacement than as a load of laundry.
One laundry load in dryer = one gallon of gasoline
Conveniently for the purposes of our math, one full load of laundry takes about an hour to dry in our Whirlpool Quiet Dry unit. That means (assuming 20 m.p.g.) that one load of laundry = one gallon of gasoline ($3).
That’s powerful incentive to hang at least some of our clothes out to dry rather than chucking them into the dryer.
In fact, when we hang a full laundry load out to dry, we save not only the extra $2.45 in gasoline replacement costs, we save the 55 cents we would have had to pay to Xcel Energy for the electricity needed to dry that laundry.
As you might imagine, since our solar system went online on June 28, 2010, I’ve been hanging a lot of laundry up to dry, and so has my wife – she’s graciously agreed to go along with my PV + EV mania. (BTW, in case you’re wondering, I do quite a bit of the laundry in our household).
Let’s crunch the numbers for a whole year so that we can see what the long-term “gasoline” savings of a load of laundry look like for an electric car owner in Xcel Energy territory:
- Four loads of laundry hung out to dry per week x 36 weeks
- 20 kWh (5 kWh x 4) x 36 weeks = 720 kwh
- 720 kWh = $79 worth of electricity (11 cents per kWh)
- 720 kWh (1 kWh = 4 EV miles) = 2,880 EV miles
- 2,880 miles ÷ 20 miles per gallon = 144 gallons of gasoline
- 144 gallons of gasoline × $3 = $423
It pays to hang your clothes out to dry
As you can see, it pays to hang at least some of your laundry out to dry. This is true whether you own a home solar system like we do (ours is a 5.59 kW system), or you don’t. With a home solar system, you essentially net the full $423. Without it, you still come out $344 ahead because you save the electricity for your electric car as a gasoline replacement rather than using it all to power a clothes dryer.
Admittedly, I’ve drawn a simplified picture here – a more efficient clothes dryer than ours makes the numbers look different . So do different utility rates and different per gallon gasoline costs and different m.p.g. rates.
Climate is another factor. We live in a perfect clothes drying climate. For example, on Sept. 5, 2010, when I hung my most recent two loads of laundry out to dry, the outdoor temperature was 90 degrees and the relative humidity 16 percent. Not everyone is as lucky as those of us in Colorado in terms of sun and humidity. On the other hand, tens of millions of Americans live in the arid, sunny American Southwest.
Let the sun save you money
The bottom line: Hanging out your clothes to dry and saving the electricity a dryer would eat up can potentially save you a lot of money when you look at the equation in terms of the saved kWh going to power an EV.
Did I mention that hanging clothes out to dry is also better for the environment?
In the U.S., the average household produces 2,224 pounds of CO2 via its clothes dryer.
On top of the environmental benefits, if you have a home solar system and an EV, or will soon have an EV, hanging as many of your clothes as possible out to dry will also allow you, me, and all the rest of the clothes-lining EV-ers and PV+EVers to hang something else out to dry: Big Oil!
If that’s not enough incentive for you to start showing your wet underwear to your neighbors, then what will be?