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Planning on going fully solar and wind on an off-grid property in my old age.
this post was submitted on 09 Apr 2024
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I understand the desire completely, though I suspect that being grid-tied is cheaper in most locations:
- wind is a lot cheaper with bigger turbines, which don't make sense for individuals (though community ownership would be reasonable)
- grid-tied systems are a lot cheaper than fully disconnected ones in most locations, and need a lot less storage, since they move electricity from where the sun shines or the wind blows to where people are
You forgot to mentioned being grid tied also enables the use off excess energy. Being off grid can be a waste.
Though while you save some in upfront costs, you loose out on the benefit of eliminating an ongoing cost thanks to still requiring a connection. Given how solar and battery prices continue to drop, it’s likely they will eventually hit the point where it may be cheaper with inflation to buy now and save later when it comes to retirement.
It's not just the upfront savings; it's that it takes truly huge amounts of storage to deal with intermittency in one location. You need a lot less storage in the aggregate if you can move power from one location to another. This makes systems where almost everybody is connected cheaper for society as a whole.
You need less on a social scale if everyone is interconnected obviously, but at the individual level it may well cost more. People were doing household scale off grid with a pile lead acid for decades after all.
Households don’t necessarily need that much power, and while heat pumps change that up north in the winter, when it comes to modern day solar off grid you often use two to three times the inverting capacity worth of panel, precisely because it allows for reliable near full power generation on cloudy or snowy days.
I've lived with one of those systems:
- it didn't use the electricity for heating, cooling, refrigeration, water heating, or cooking
- It was 12v electricity, so you had to have specialized lighting and other appliances to use it
- you tended to have limited electricity available in the winter
It's not the same as the almost-always-available situation that people expect.
So have I, and nowadays it very much is almost always available situation people expect, even for fully electrified homes. PV paneling cheaper per square m than fencepost plus being able to store a full weeks worth of average amarican home consumption for 20k of new battery have combined to make generatorless off grid a lot more practical.
Yes, if you're not running HVAC in a northern climate. Those use enough electricity that grid-connection is incredibly valuable.
Even then, modern heat pumps on average only use in the neighborhood of .5k to 2k kwh during the coldest months in southen Canada/ northern US, that is definitely within the capabilities of an reasonably affordable properly designed off grid solar system. Hence why I suggested it was reasonably doable for a fully electrified home, and will likely be much cheaper by the time your average lemmy user is building or buying their dream home.
Currently such a system is already in the cost range of twice that of a inground pool, by far the two most expensive parts of it, overpanneling and battery storage are plummeting in cost.
I think you underestimate what it takes to heat an older structure in the north. 7kw is pretty common for whole-home retrofits. Enough to run that all night in winter during an extended cloudy spell means a lot more panels and a lot more storage.
Are you suggesting a 7kw heat pump, or 7,000kwh/m highest hearing load? Because the former would already come out to about 2.5k kwh assuming a 12h duty cycle for 30 days, while the latter would cost over a thousand dollars a month to run at average US electricity prices during the month of highest load.
For reference the typical heat pump in the typical amarican single family house consumes 5.4k kwh in an entire year.
the typical heat pump in the typical amarican single family house consumes 5.4k kwh in an entire year.
I think you googled, took the first result, which was:
https://www.energysage.com/electricity/house-watts/how-many-watts-does-an-air-source-heat-pump-use/
and it says "Based on an EnergySage analysis of a Department of Energy database, a typical heat pump in a typical home uses 5,475 kilowatt hours (kWh) per year"
but then treated it as meaning a "about 5½kwh" instead of 5475kwh.
The two are very different numbers, and most heat pumps in the US are currently installed in warmer locations, so you can expect utilization in colder places to be appreciably higher.
A heat pump won't be running at peak output all year long, but during winter in the north, it's likely to do so every night for a week at some point.
A $1000/month heating bill isn't that rare in some parts of the US in winter.
In most (sane) numbering systems, you can use a k in place of thousands, m in the place of millions, etc. Becuse all the numbers around the scale of energy use involving the entire monthly power consumption use of a heat pump in a cold climate as well as solar production and storage needed are in thousands, you will note I wrote all the relevant numbers with the abbreviation k, so 5,475 kwh is equivalent to 5.4k kwh.
Admittedly 5.4 mwh would have been more clear, but because megawatt hours is less commonly used and would involved useing two diffrent units next to each other I used thousands of the same unit for consistency. Please go back and re-read all of my comments with this new knowledge in mind.
Yes, many heat pumps are installed in warmer climates, though that is changing, but blowing through the entire yearly national average in three weeks and then doing it again is lot of power for a climate contentious and thusly presumably well insulated off grid modern house to use. (Also, if we go back to what this conversation is about, the original commenter gave no indication that they were in a very cold climate with thousand dollar a month heating costs in the first place.)
For a modern well-insulated structure, sure. But a lot of US housing was built without insulation. And people live in it and would prefer to retrofit.
We are literally talking about whether it is practically possible for a major renovation to a lifelong dream home. If they are in love with an old poorly built and insulated home in a very cold area then yes, in a few decades when this do this they will have to have it insulated to at least modern standards and of doing so it’s likely worth it to go to far better, but that is a very long way from your position that no one could even think about it being feasible for anyone in a few decades.
Can I be sure what will happen decades from now? No, but I can say for sure that at the moment, if you want to add insulation to an existing older structure, and not do a complete rebuild, you end up with a structure which isn't anywhere near as well insulated as a newly-built structure designed for efficiency.
Again, where are you getting the idea that the original commenter has to be talking about being set on a old, poorly insulated home?
That's pretty much what most retrofits in the US look like.