Energy Self-Sufficiency? Still Just A Dream

martedezena Haziran 15, 2022

One of our goals is to someday get off-grid by becoming energy self-sufficient. Of course, the term off grid typically implies electricity, so I suppose it would be possible to be off grid but not entirely energy self-sufficient. I could make my own electricity but still purchase kerosene, propane, natural gas, home heating oil, even candles. Our home is all electric however, so for us, making our own would make us basically energy self-sufficient as well.

About the only things we've done toward this goal (in all our spare time ;), has to been to observe sun and wind patterns throughout the year, and keep track of our electric usage. We've observed enough to know that there would be some limitations with either of these systems. We've kept track of our electrical usage long enough to know that even though we consider ourselves frugal in that area, we still have a long way to go.

One thing that's puzzled me, is how to figure out what size alternative energy system would meet our needs. Most things are rated in watts. For things like solar panels or wind turbines, this tells me how much electricity they can generate. But how do I know how much I'll need? When I look at my electric bill, it tells me how much I've used in terms of kilowatt hours. Things like appliances and light bulbs are also rated in watts. In this case, the wattage tells me tells me how much electricity is needed for the device to operate. However, I can run a 60 watt light bulb for 3 minutes, or for 3 hours. Obviously the amount of electricity I use won't be the same. Kilowatt hours are the actual amount of electricity I use to run that light bulb. I pay for what I use, so my electric bill specifies charges for kilowatt hours.

So how do I get to there from here? After a little research, here's what I've learned about using my electric bill to determine the size solar system I would need.

First I need to know how many kilowatt hours I use on a daily average. Last year we used a total of 10,751 kilowatt hours.

10,751 kWh / 12 months = 896 average kilowatt hours per month

896 kWh / 30 days in a month = 30 kilowatt hours per day

As an aside, I have to say that averages do have their limitations. The actual range for daily use was from 16 to 54 kWh in a given month, depending on the time of year (remember, we have an all electric home. The worst culprit are the auxiliary electric heat strips in our air source heat pump, which come on when the outside temperature it too low. Now that we have the wood cookstove to heat the back of the house, we can further decrease our electric during winter months. )

By looking at a solar insolation chart like this one, I know my area is rated at 4.5 solar hours per day. I divide that into my average daily kWh consumption

30 kWh / 4.5 solar hours = 6.67 kilowatts

Because solar panels are only about 20% efficient, that must be factored in as well. Actually, its the inefficiency that's factored in, so for this example, 80% or 0.8. This could be more accurately calculated from the information provided with a specific brand and model of solar panel.

6.67 / 0.8 = 8.3 kW

That gives me an idea of the size solar system I would actually need, assuming we made no other changes to our lifestyle.

There are numerous online calculators to determine the cost of installing solar systems. I used this one. It estimated my cost would be $71,040 for a system to cover 100% of our electric usage. The good news was that because of the government solar energy rebate, I'd be reimbursed $21,312, so that the system would actually only cost me $49,728. The problem with rebates of course, is that one must pay the entire cost upfront and then wait until tax time to get the rebate. That's great if one can afford it in the first place, but for those of us who can't, it would be more helpful to receive a grant to cover the $21K. Of course that's assuming I'd have the remaining $50K. Even at that, I figured it would take 42 years for the thing to pay for itself, assuming my electric bill remained the same. We don't do loans, but hypothetically, if I took one out to purchase the system, the additional interest would mean my energy self-sufficiency would cost me more than simply buying electricity from the power company. That of course was just one estimate, and if one can DIY, especially with used parts, the cost would be far more manageable.

Wind energy for us is even less feasible. According to the US Wind Resource Map, we live in a virtually zero wind resource area. From my observations I know that this is not specifically true, but I do know that the only time it gets truly windy here, is this time of year, in spring, or late summer, when we get hit with the remnants of a hurricane. In fact it's been so windy the past few days, that the chickens won't even go out. They all stay huddled on the lee side of the goat shed. Even so, this is not enough to justify spending tens of thousands of dollars on a wind turbine that would only be productive a few weeks out of the year. (Unless of course I used my solar tax rebate ;)

So how close are we to actualizing energy independence? About as close as the man in the moon.