How much electricity will we need?

We are still working on finding a builder for our custom home in Colorado. We are very close to making a decision. In the meantime we are thinking about all the different parts and peices that will make the home work. One of the most important parts is our solar power system.

The house is going to be tied to the power grid. So the solar power system will indirectly generate the power we use giving us a $0 power bill each month. That means we need to build a solar power system that is at least as large as all of the electricity our home will use. An extra complexity is that our local power company only allows us to have a system that is 120% of our overall usage.

So we used this online calculator for an off-grid solar system to get an estimate of what our home will use on day 1, plus we added an Electric Vehicle Level 2 charger. We figure that within 5 years we will have an EV and will want to be able to fast charge it at home.

Here are the numbers:

ApplianceQuantityWattsHours On per DayWatt Hours per Day
LED Bulb – 60 Watt Equivalent251361950
Fridge – 20 cu. ft. (AC)135341412
TV – LCD215092700
Smart Phone- Recharge26336
Water Heater – Electric145001.56750
Oven – Electric1120011200
Clothes Dryer – Electric130000.51500
Clothes Washer18000.2160
TV – LCD2150123600
Circular Saw 8-1/4″1140011400
EV Level 2 Charger111500111500
System Calculation Results
Killowatt Hours per Month:1,969 kWh
Peak Load:30,404 watts
Sun Hours:4.75 hours/day
System Size:16.58 kW
Just a rough idea that we will need a 16kW solar panel array at some point.

This helps us understand that we will want to max out our south facing roof with 42 solar panels. At 330Watts per panel that gives us just over a 13kW system to start with. We still have the roof on the garage which could handle another 40 panels. So we will want to get an Inverter that allows for expansion.

The next step is working with the power company to get approval. Then figuring out if we want or can roll this equipment into the mortgage of the house.

Lots to think about.


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