Solar · The threshold
Which is worth saying first, because the honest answer for most households is that a smaller system, used well, is doing its job. This page is about telling the difference between a system that has genuinely run out and one that had a hard week.
First, the honest part
Every off-grid system has a worst stretch. That is what worst-month sizing produces on purpose: a margin that is thin in December precisely so it is not absurdly oversized in June. A tight week is the design working, not the design failing.
The preparedness industry is very good at converting one uncomfortable week into a five-figure purchase. Before spending, it is worth separating a bad stretch from a real limit, and the difference is a pattern over a season rather than a memory of one January.
If you arrived here from 200W Solar or the rooftop solar primer, the most likely correct answer is that those pages still fit your situation. Nothing below is a ladder anyone needs to climb.
Five signals
Each of these is a pattern rather than an incident. One of them is worth investigating. Three of them together is a system that has reached its limit.
Not on the bad days, on the ordinary ones. A system that finishes most winter days lower than it started is not recovering, and chronic partial charge shortens the bank as well.
If a second overcast day means shedding loads, actual autonomy is well below what was designed for, and the local weather will produce longer stretches than that.
A generator for the worst week is sound design. A generator running most weeks means the system is not carrying the property, and the fuel is now a recurring cost.
A hard physical limit rather than a judgement call. When usable roof, orientation or shade caps the array below what the arithmetic asks for, the mounting question moves to the ground.
A well pump, a workshop, a freezer for a season's harvest, someone working from home. New permanent load is the most common honest reason a working system stops being enough.
Cheaper first
A watt-hour not used is worth more than a watt-hour generated, because removing a load shrinks every part of the system at once. Fewer panels, a smaller bank, lighter conductors, smaller conversion hardware. Generation has to be bought and then maintained for decades.
Most households are wrong about where their power goes. The power use guide and the needs calculator will usually find something surprising, and it is often not the appliance anyone suspected.
The load that never switches off is divided by worst-month sun like every other watt-hour. In a two peak sun hour December, each watt of constant draw needs roughly fifteen watts of panel behind it.
An array tilted for annual production is giving away December. Re-angling an existing ground mount, or simply clearing it reliably, can recover more than new panels would add. See mounting and tracking.
Laundry, pumping, workshop tools and water heating done at midday come straight off the array rather than through the bank, avoiding storage losses entirely. Costs nothing but habit.
Worst-month sizing produces a large summer surplus by design. A diversion load gives that surplus a controlled destination once the bank is full, typically a resistive element heating water or space. It does not help in December, and it makes the other eight months considerably less wasteful.
What it asks
Property-scale generation is a different kind of commitment, not simply a larger version of the same one. Three things change, and they are worth knowing before rather than after.
A folding panel goes in a cupboard. A ground mount has foundations below the frost line, a permit, an inspection, and a place on the property it will occupy for decades.
Larger banks store more energy and deliver far more current into a fault. That is why wiring and code is the one page in this section that does not hand you a procedure.
No utility crew arrives. Cleaning, snow clearing, connection checks and bank monitoring become household work, forever. A system nobody services fails quietly.
If you are going ahead
Each one starts from a number the previous one produced. Taken in sequence they get a property from a measured daily load to a specified system.
Daily load, standing draw, and worst-month arithmetic.
2Days of autonomy, usable capacity, and the cold rule.
3Conversion hardware, and the surge that starts a pump.
4Where the array goes, and why panels beat moving parts.
5What the system demands, and why this part is licensed work.
6Short days, snow, cold banks, and the compound week.
Other sources
Where ground, shade or winter caps what solar can do, the property's other resources are worth assessing honestly. These sections are in progress and will link here as they publish.
The strongest of the three where it exists, because it runs day and night rather than in daylight. Continuous output reduces the storage a property needs. Most readers will not qualify, and the honest first question is whether the resource is really there.
Often strongest in the season solar is weakest, which is genuinely attractive. It is also the source most often oversold at this scale, needs real height to reach clean air, and has moving parts in weather.
The unromantic answer that is frequently correct. A generator covering the worst stretch is usually cheaper than the storage and panels required to eliminate it, and it turns an impossible week into an inconvenient one.
One caution that applies to both water and wind. A turbine disconnected from its load while still turning loses the braking that load provided and can overspeed. For those sources a diversion load is a safety requirement, not an efficiency improvement.
Pace
Nothing about property-scale generation rewards speed. The measurements that matter take a season to gather, the permit conversation is better had early, and equipment bought before the arithmetic is done tends to be the wrong equipment.
A reasonable path is to spend one winter measuring, one spring reducing load and fixing angles, and only then decide whether the system that remains is genuinely short. Many households find the gap closes without buying anything.
If it does not close, the arithmetic in this section will still be here, and you will arrive at it with real numbers from your own property rather than estimates.
Next
The hub for this section, with all six guides in sequence.
Back to the hubThe wider section, covering water, wind, biomass, engines and site-specific sources.
See all six areasOr step back to Energy for the household-scale guides, which is where most readers are best served.
Sources
Whether a household has outgrown its system is a question about that household's own measurements across a full season. No general figure answers it.