My family and I have been living in a solar powered house since December of 2015.
Our home was a new construction, built with a focus on low energy consumption. The finished space for this home is 1800’ (basement and bonus room still unfinished). It has 2.5 baths, central air, microwave, dishwasher, etc – basically all of the modern conveniences.
To drive by our home, you would never know that the house is off-grid. And for those of you who aren’t familiar with off-grid living, this means that we have no connection to the electric utility. In other words, no power lines, no meter box and best of all, no electric bills!
For the record, this has not been easy. The learning curve has been significant! But after several years of real world practice, I would sum it up like this.
You build a solar powered house by knowing exactly how much power your lifestyle requires and then installing the appropriate number of solar panels.
How To Calculate Power Consumption On A New Construction
It might sound like a ‘Catch-22’ saying that in order to correctly build a solar powered house, you first need to know how much power this house is going to use.
After all, if you haven’t received an electric bill yet, how can you possibly KNOW, with any level certainty, exactly how much power this new home will consume?
The answer is actually easier than you might think.
You calculate the anticipated power consumption by adding up the power consumers – namely all of the electrical devices you plan to use in the new house; fridge, lights, microwave, ect.
For me, the easiest way to do this was by dealing in watts. Yes, there are other ways to understand the electrical power consumption of your house, but solar panels are rated in watts. So, for the sake of keeping it simple, stick with watts!
Here is, roughly, how the math works.
We have 3 bedrooms with ceiling lights. These fixtures all have 8 watt LED bulbs installed.
Two of the bedrooms have 2 bulbs each (4 total) with the final bedroom having 3 bulbs. This gives us a total of 7 bulbs.
If all 7 light bulbs are lit, with each bulb consuming 8 watts of power, then total consumption for the 3 fixtures is 56 watts (7 bulbs * 8 watts each = 56 watts total).
Now we factor in how long the lights are on.
If all three lights are left on for 8 hours, then the watts consumed grows by a multiple of 8.
56 watts (for the 3 light fixtures) * 8 hours of use = 448 watts total consumed.
Using this total, we can now see that it would require one 448 watt solar panel to work one hour in order to generate enough electricity to run those three lights (7 bulbs @ 8 watts each) for eight hours.
This is why it’s important to turn your lights off!
To be honest, the idea of calculating all of this was extremely daunting for me. After all, there are a LOT of electrical devices in a house. But I soon found, that once my spreadsheet was started, adding items to it, as I came across them, was more than manageable.
## Note ##
Do not be too discouraged if you are unable to find watt numbers on every electrical device in the house. Sometimes, that information is not easily obtained. For example, I was unable to find any info regarding our water pump. Just keep the unknowns listed when planning for your solar array – and then guess high.
House Load & Solar Panels
Once you have a complete list of the power consumers, and thereby, a fairly good understanding of what your electrical demands will be, then it is time to consider solar panels and what you can realistically expect.
Solar panels are amazing things, but they do have… ‘quirks’. The following is a brief list of things to consider when planning to build a solar powered house.
- Panel Watt Ratings – As previously mentioned, solar panels are rated in watts. However, it is important to know that solar panels are built for specific power ratings (think groups). You will see numbers like 320, 365, 385, etc. This is because each panel has a certain number of solar cells embedded in them, with the more the solar cells delivering more power.
This is important as you will most likely not have an exact match between panel watt rating and the house load you calculated earlier. For example, to my knowledge, there is no such thing as a 448 watt solar panel as described in the room light example mentioned above.
In a real world scenario, you would need 2 panels with, at least, 260 watts worth of power production each. Granted, this gives you 520 watts (260 * 2) when you only needed 448 watts. But because panels are built in limited sizes, you will have to plan you solar panel purchase accordingly.
To understand this better, please read, ‘How Many Solar Panels Do I Need?’
- Optimal Rating Vs. Realistic Output – One thing that every potential buyer should know, is that while your solar panels may be rated for a specific output, that doesn’t mean maximum output will be achieved.
This is not necessarily the fault of the solar panels.
Photovoltaics work best in direct sunlight. And there are a number of things that can interfere with this process. Clouds, dust and pollen are just a few of the every day occurrences that can prevent your solar panels from producing at their best.
Keep this in mind when planning your purchase.
- Location – The arrangement of your solar array will play a big role in how well your solar powered house performs. Ideally, your solar panels will face true south and tilted to an angle that matches your latitude.
For example, Chicago’s latitude is roughly 42 deg. For people living in Chicago, solar panels will produce more if tilted to an angle of 42 degrees, rather than shallower angles like 20 or 15 deg.
But not every location will be completely accommodating. For some, even a southern facing alignment will not be possible. It is critical that you understand where and how your solar panels will be mounted as this will directly impact the amount of power they produce.
To understand this better, please read, “Should Solar Panels Face South?”
Clarify Your Goals
If you are an individual, like most of us, who is intimately familiar with the concept of a budget, then understand that compromises will have to be made.
Building your solar powered house will be easier if you know, ahead of time, what goals you want to accomplish.
You can start by asking yourself these three questions:
- Do I want a Net-Zero home or just no electric bill? – For those who aren’t familiar, a Net-Zero home is an all electric house that is equipped with enough solar panels to provide 100% of the needed energy. This is similar, but not the same, as just having no electric bill.
It is much easier to achieve little or no electricity costs for your home if you shift away from electric appliances. Two easy examples of this would be to install a gas range and a gas hot water heater. In this case, your solar array could be smaller (and consequently, less expensive to install), but you would have the additional cost of a gas bill.
- Do I want to be grid-tied or off-grid? – Simplified, a grid-tied house is connected to the electric utility and a off-grid home is not.
It should be understood that home power systems that are grid-tied, generally have a much lower cost to install than off-grid systems. This is because grid-tied systems utilize the electric utility as means to pull power when panel production is low.
By comparison, off-grid systems utilize onsite storage (whole house batteries) which have a significant cost.
However, it should be noted that grid-tied systems will disengage in the event of a blackout, leaving users in the dark where off-grid systems are unaffected by any event involving the power grid.
For an in-depth look at this, please read, “Off-grid Vs Grid-tied Solar.”
- Is solar allowed at my location? – For some, it comes as quite a shock to learn that just because you have the will and the money for solar panels, that doesn’t mean that you will be allowed to install them.
For grid-tied users specifically, permission must be given by the electric utility as you will be utilizing their infrastructure. More notably, permission can be later denied if your home power system is deemed harmful to their service.
For off-grid fans, permission from the township must be obtained. Do not simply build your house and expect them to go along with it. I can tell you from personal experience, sometimes a township is banking on local home owners to pay for new infrastructure.
Build An Energy Efficient House
No article regarding the construction a solar powered house would be complete without addressing the home’s efficiency.
The more time and thought you put into things like insulation and air-flow – both in stopping heat loss from the home and moving heat through the house – the less demand you will put on your solar panels.
For example, our home is heated by a single pellet stove. Generally, the heat output of this stove is around 20,000 btu’s – which is roughly the equivalent of a hair-dryer. (It’s probably worth mentioning that we live in Michigan).
Another way to help you with your energy consumption is by installing energy efficient appliances and by utilizing natural light whenever possible. These two things can help you more than you might imagine.
Typically, our house consumes around 12kW to 15kW a day. This is considerably less than the average 30kW of a conventional American home.
Clearly, if you do your homework, you can save a LOT!
Ask anyone who’s been through it, building a home is no small task. It can be incredibly stressful, with unanticipated (expensive) surprises coming at you, seemingly from every angle.
But regardless whether you built something extraordinary, like a solar powered house, or a simply a comfortable place to raise a family, the more thought you spend ahead of time, the more likely you will be pleased by the result.
And to all of those who choose to undertake this incredible endeavor… Good Luck!