Sixty-eight percent. That's what the little hygrometer on top of our dryer read in July of our first summer here, and the basement smelled exactly like that number. Damp cardboard, old block walls and a faint mustiness that followed the laundry upstairs. Towels I'd hung on a line by the furnace stayed damp for a day.
A few weeks later we bought a Midea 50-pint dehumidifier for $229. It brought the basement down to 50 percent and kept it there, and the smell faded within a couple of weeks. What I never did last year was figure out what it was costing us to run. With summer starting again, I finally measured it.
How I measured it
Gary lent me a plug-in watt meter, the kind you plug into the wall and then plug the appliance into. From the first Sunday of June to the following Sunday, it logged every watt the dehumidifier used.
When the compressor runs, the unit pulls a little over 500 watts. When it's satisfied and just sitting there with the fan off, it uses almost nothing. Over that week, it ran about six hours a day on average and used just over 23 kilowatt-hours. That's roughly 3.3 kWh a day, or about 100 kWh over a month.
For the price, I took our most recent Consumers Energy bill and divided the electric dollars by the kWh, so delivery charges and fees are baked in. It came to a bit over 17 cents a kWh at the time. A hundred kWh at that rate is about $17 a month.
That's an estimate, not a meter on the house. Summer pricing has different rates at different times of day, and humid weeks in July will run longer than a mild week in early June. But it's close enough to decide with, and it matches the bump we saw on last summer's bills well enough that I believe it.
What $17 a month buys
Our basement is unfinished: painted concrete block, glass-block windows that don't open, about seven feet to the joists. It holds the laundry, the furnace, the water heater, the sump pit and a lot of storage boxes. Here's what changed between 68 percent and 50 percent:
- The musty smell is gone. Guests don't notice it, and Tessa stopped spraying things before people came over.
- Laundry dries on the line in an afternoon.
- The cardboard boxes stopped going soft at the bottom.
- Tools I keep down there aren't getting the orange bloom of rust they had last July.
We run it roughly May through October. In winter, with the furnace running, the basement air is dry enough on its own that I unplug it. So the yearly cost is something like $85, which feels reasonable for a basement we can store things in without worrying.
Setup, and the mistake I made last year
For the first month we owned it, I emptied the bucket twice a day. Then I connected a garden-style hose to the drain port so it could run straight to the floor drain about eight feet away. The first time, I laid the hose across the floor with a slight loop up over the edge of a rug. Water backed up into the unit, the bucket-full light came on, and it shut itself off for a day and a half before I noticed. The basement went right back to smelling like a basement.
The fix was simple. I set the dehumidifier on two concrete blocks so the drain port sits higher than every inch of the hose, and the hose runs downhill the whole way to the drain. It hasn't stopped since.
A few other things I do now:
I set it to 50 percent, not lower. Going lower made it run much longer for no difference I could smell. I rinse the filter every couple of weeks, which takes thirty seconds. And I keep it out in the open, a few feet from walls and the stacks of boxes, so it can actually pull air.
The tradeoff nobody mentions is heat. A dehumidifier puts out warm air, and the basement runs a couple of degrees warmer when it's working hard. In summer that's mostly fine. It's also a little loud, a steady fan hum you can hear through the floor in the kitchen if everything else is quiet.
When I told Tessa the number, she looked at the hum coming through the floor vent and said, "It's the only appliance in this house I've ever thanked out loud." The watt meter went back to Gary's garage, and the dehumidifier went back to work.
