About our Fridge
Bernice picked out the Frigidaire 11.5 cu. ft. top freezer refrigerator. We've been using it in the little 400-square foot carriage house that we're renting during the build and think it's a great choice for a tiny house. It's narrow, just 24" wide, and runs very quietly — very important when you're sleeping in the same room with it!
One question we had when we bought it was exactly how much energy it would use, since we're going to be running off solar panels part of the time. But how do you know?
Energy by the Label
Measuring Real-World Energy Use
The numbers on the label are based on measurements under laboratory conditions, But how well does this predict actual energy usage? Once we had the refrigerator set up here and filled with food, we were ready to measure how much electricity it used in real life.
This is easy to do with a special electrical meter called a "Kill-A-Watt Meter" that measures many different electrical parameters at once -- Volts, Amps, Watts, Volt-Amps, Frequency, Power Factor, kiloWattHours, and Hours. It's the last two that are of interest to us, the meter watches the power use over a period of time, and continuously records the total kWh used and the run time.
The Kill-A-Watt is easy to use, you just plug it into an outlet (at the end of an orange extension cord in this case) and then plug the refrigerator (grey cord) into the meter. It will accumulate data as long as it's plugged in, just unplug it from the wall to reset the kWh and time counters to zero.
These photos show it after it ran for a bit over a day. Power consumption was 0.98 kWh over a period of 31:17 = 31.28 hours. We can multiply by 24 hours per day/31.28 hours to get daily power usage, 0.98 x 24/31.28 = 0.752 kWh per day. This tells us our actual usage was about 90% of the 0.852 kWh per day predicted by the label. Again, dividing by 24 hours per day and multiplying by 1000 W per kW gives us 0.752/24 x 1000 = 31.3 W used if it ran continuously.
We ran a much longer test over a period ending 11/17/2016, using 39.43 kWh over a period of 985 hours (41.04 days) for a daily usage of 39.43/41.04 = 0.961 kWh per day. Power used is 0.961/24 x 1000 = 40.0 W used if it ran continuously. Here in Phoenix, Arizona the temperatures were quite high through October, so the longer time sample included hotter weather when the refrigerator would have been running more during each day.
The Bottom Line
So when all was said and done, for our fridge the energy usage label gave a very good estimate of what you can really expect! The label said we could expect to use 0.85 kWh per day, and our measurements showed we used between 0.75 and 0.96 kWh per day.
Or, Alice's Adventures in Salvageland
We picked up a recycled RV water tank that we'll use for our grey water tank. We found it at a great surplus place here in Phoenix. Arizona RV Salvage. You should definitely check them out if you're building your own tiny house, they have a huge lot and several buildings packed with salvaged recreational vehicles and parts from those already disassembled. They gave us a great deal on a bunch of essential tiny house bits! We got the grey water tank, a NEW 3 gallon per minute 115V water pump, a valve for the grey water drain, and a nifty electronic display that will show us our water tank levels.
The opening in our floor in between two of the steel cross struts is 72" long x 30.5" wide x 10" high. Our goal was to find a tank that would fit in there that was our target size of greater than 40 gallons. This one is 62” long x 23” wide x 9” high and holds about 50 gallons. This is a great fit in the floor opening and allows room on the sides and ends for fittings and insulation.
More construction pictures! After a brief lumber delivery glitch Michael had the wood for the floor, and the steel belly board and floor joists are in place. The gap in the floor is where the grey water tank will go, the belly board in that section will be lower to accommodate it.
Michael has attached the first of the steel "belly board" plates together, and has welded brackets onto the trailer to attach the floor joists. Next is cutting one of the cross members to make room for the grey water tank, and constructing a cage to support that.