Pair your load with the right power.

How many solar panels do I need to power my house?

“Panels” is the wrong unit — one is anything from 100 W to 550 W. The answer is kilowatts of array and kilowatt-hours of storage.

Where those two numbers come from, and “my house”

Both start from the same place: the list of things you actually want to keep running, and how long each one runs.

A balcony or off-grid system that carries a fridge, the internet and some light is a product you can buy and plug in, and this page will name one. A whole-home grid-tied system is a roof survey, a service panel, a permit and a licensed installer — this page will give you the same sizing numbers for it and then stop, because choosing an installer is not something this site does.

Loading the plan you were sent…

Reading the configuration in your link and re-running the engine on it. Underneath this panel is the page's built-in WORKED EXAMPLE — not your shared plan; it is covered for a moment so it cannot be mistaken for your answer.

Your shared plan could not be loaded. Everything below is this page's WORKED EXAMPLE — not your shared plan. Reload, or use the controls to rebuild it.

Worked example

Full-size refrigerator + Router + modem + LED light bulb × 6

A stock system covers this 0.5 kW

Your list draws 1,595 Wh a day at the socket. Dividing by the 3.5 h floor of the sunlight band you picked gives the array; multiplying by 1 day of autonomy gives the storage. Both are FLOORS at standard test conditions. A real array loses output to heat, dust, angle and cloud, and WattPair has no measured derate curve to apply — so this is the smallest system that could work, not the one to buy.

officialverified 2026-08-01appliance library

Suggested array 0.5 kW
Load vs output 14%

Sales restriction US-UT only

Due to restrictions under the H.B. 340 Solar Power Amendments, this product is only available for sale and plug-and-play installation in Utah. Please note that you are solely responsible for ensuring your installation and use of the product strictly comply with applicable laws and regulations regarding where the product is intended to be installed/used.

Utah H.B. 340 Solar Power Amendments · checked 2026-08-01

Array, at least 0.5 kW at standard test conditions — a floor, not a plan
Storage, delivered 1.6 kWh at the socket, not the number printed on a battery

1,595 Wh a day ÷ 3.5 h of peak sun = 456 W of array · 1,595 Wh × 1 days = 1,595 Wh of storage

Where the energy goes

Appliance Running draw Duty-weighted Hours a day Energy a day
LED light bulb × 6 51 51 5 255
Full-size refrigerator 55 47 24 1,122
Router + modem 9.1 9.1 24 218

“Duty-weighted” is the draw averaged over how much of each hour the machine actually runs — a refrigerator compressor is not on for sixty minutes in sixty. That correction is the difference between this figure and the label-wattage arithmetic every other sizing page does, and it is roughly a factor of two on refrigeration.

Products that can take this job

Each row below was checked by running the compatibility engine against your load set and the solar engine against a real array built from panels in this library. A product with no legal array or no headroom says so on its own row instead of being quietly dropped.

  • EcoFlow STREAM Ultra US · home storage Runs your list

    Sold in US-UT only. Due to restrictions under the H.B. 340 Solar Power Amendments, this product is only available for sale and plug-and-play installation in Utah. Please note that you are solely responsible for ensuring your installation and use of the product strictly comply with applicable laws and regulations regarding where the product is intended to be installed/used. Utah H.B. 340 Solar Power Amendments

    US-UT only · no button Out of stock at the official store · checked 2026-08-01

    Load vs output
    14%
    Nameplate
    1,920 Wh
    Usable
    — no published figure

    Verified array 4 × Renogy 100W 12V Monocrystalline Solar Panel (Compact Design), 2 in series × 2 strings — 400 W of panel, 401 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    The largest legal array the engine could form from the panels in this library is 400 W, short of the 456 W suggested. The shortfall costs charging time, not safety.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

  • EcoFlow DELTA Pro 3 US · xl 4k plus Runs your list
    Load vs output
    2.9%
    Nameplate
    4,096 Wh
    Usable
    — no published figure

    Verified array 3 × Renogy 200W 12V Monocrystalline Solar Panel, 3 in series — 600 W of panel, 600 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

  • Anker SOLIX Solarbank 3 E2700 Pro EU · home storage Runs your list
    Load vs output
    9.6%
    Nameplate
    2,688 Wh
    Usable
    — no published figure

    Verified array 3 × Renogy 200W 12V Monocrystalline Solar Panel, 3 in parallel — 600 W of panel, 600 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

  • EcoFlow STREAM Ultra EU · home storage Runs your list
    Load vs output
    9.6%
    Nameplate
    1,920 Wh
    Usable
    — no published figure

    Verified array 4 × Renogy 100W 12V Monocrystalline Solar Panel (Compact Design), 2 in series × 2 strings — 400 W of panel, 401 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    The largest legal array the engine could form from the panels in this library is 400 W, short of the 456 W suggested. The shortfall costs charging time, not safety.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

  • EcoFlow DELTA 2 Max EU · large 2k 4k Runs your list
    Load vs output
    4.8%
    Nameplate
    2,048 Wh
    Usable
    — no published figure

    Verified array 4 × Renogy 100W 12V Monocrystalline Solar Panel (Compact Design), 2 in series × 2 strings — 400 W of panel, 401 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    The largest legal array the engine could form from the panels in this library is 400 W, short of the 456 W suggested. The shortfall costs charging time, not safety.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

  • EcoFlow DELTA Pro 3 EU · xl 4k plus Runs your list
    Load vs output
    2.9%
    Nameplate
    4,096 Wh
    Usable
    — no published figure

    Verified array 3 × Renogy 200W 12V Monocrystalline Solar Panel, 3 in series — 600 W of panel, 600 W accepted legal

    The panel No verified purchase link — the maker’s catalogue does not list this exact SKU.

    This brand publishes no usable-capacity figure for this model — only a nameplate. Your 1.6 kWh target cannot be checked against it, and nameplate watt-hours are not the same number. Treat the nameplate as an upper bound you will not reach.

Product page → Out of stock at the official store · checked 2026-08-01 There is no buy button for the EcoFlow STREAM Ultra: the manufacturer restricts where this product may be sold and installed (Utah H.B. 340 Solar Power Amendments). The link is to the official product page instead, so you can check your own location against the statement above.

If this is a whole-home, grid-tied project

The two numbers above are still the right starting point — a load study begins with exactly this arithmetic, and arriving at a professional conversation with your own daily watt-hours already worked out changes that conversation. What comes next does not happen on a calculator: a roof or ground-mount survey, a service-panel assessment, an interconnection application, and a permit.

Choosing an installer is outside this site’s scope. WattPair does not match, rank, rate or refer installers, and this page has no form, no quote request and no email capture — nothing here collects anything about you. There is also no cost, payback, rebate or credit figure anywhere on this page: incentive rules in this area change month to month, and a number that ages badly is worse than no number.

The legal and practical background — whether plug-in solar is permitted where you live, and what a balcony array really produces — is the Knowledge channel’s job, and it is answered there: the three guides at the foot of this page cover the state-by-state check, the output a real balcony array reaches, and how many panels a day’s energy actually takes.

Not your list? Change it

Everything above recalculates as you change these. Nothing is sent anywhere — the same engine that built this page runs in your browser on the same data.

The sunlight bands are WattPair’s own conservative enumeration (wattpair_enumeration) — not a measurement, not a dataset this site holds, and not a figure for your address. Sizing uses the bottom of the band you pick. For the real number, look your own location up: NREL PVWatts (US) , JRC PVGIS (EU + worldwide) .

What you want to keep running

Computing

Cooking

Cooling

Heating

Internet

Laundry

Lighting

Medical

Power tools

Pumps

Refrigeration

RV & marine

TV & entertainment

The same list, four climates

Every figure below is this page’s own engine run at build time. Only the sunlight band changes between rows, which is the point: the energy your appliances need is fixed, and the array that supplies it is not.

Sunlight band Energy a day Array, at least Storage
Low — 2.5 to 3.5 h/dayCloudy maritime climates, deep northern latitudes, a shaded or north-facing wall. 1,595 Wh 0.6 kW 1.6 kWh
Moderate — 3.5 to 4.5 h/dayMost temperate inland regions on a well-oriented, unshaded surface. 1,595 Wh 0.5 kW 1.6 kWh
Good — 4.5 to 5.5 h/daySunny mid-latitudes, tilted and unshaded, away from persistent coastal cloud. 1,595 Wh 0.4 kW 1.6 kWh
High — 5.5 to 6.5 h/dayArid high-insolation regions with a tilted, unshaded, clean array. 1,595 Wh 0.3 kW 1.6 kWh
A bigger list, moderate band Full-size refrigerator + Chest freezer + Router + modem + LED light bulb × 8 + Laptop computer, 2 days of autonomy 2,334 Wh 0.7 kW 4.7 kWh

Between the darkest and the sunniest band the same appliances need 0.6 kW and 0.3 kW of array — a difference of more than two to one, entirely from where you live. The storage figure does not move at all, because a battery is sized by the load and the nights, not by the sun.

The formula, and where each term comes from

array W = Σ (running W × duty cycle × hours per day) ÷ peak sun hours

storage Wh = Σ (running W × duty cycle × hours per day) × days of autonomy

Two lines sharing a numerator. Everything interesting is inside the summation: the duty cycle, which most sizing pages drop, and the fact that both results are floors rather than recommendations.

  • Duty cycle, not label wattage

    A refrigerator compressor is not on for an hour every hour, and a sizing figure built on its nameplate watts is roughly double what it should be. Two defensible readings of a fridge's duty cycle exist and they are not interchangeable — a regulation's formula constant and observed field behaviour — so the library stores the field figure as the headline and keeps the regulatory one as an interval endpoint. engine parameter compat.duty_cycle_point_basis · appliance_evidence

  • Hours a day is a separate question from duty cycle

    They multiply, they do not overlap. “Hours a day” is how long the machine is switched ON — a fridge is 24, a laptop might be 8. The duty cycle then says what fraction of that time it actually draws power. Setting a fridge to 8 hours because “it only runs a third of the time” double-counts the same correction and undersizes the system by a factor of three.

  • Why the array figure is a floor

    Dividing by peak sun hours gives the array that would supply the load at standard test conditions: full sun, cool cells, clean glass, perfect angle. Reality is worse, by an amount that depends on your roof. WattPair has measured no derate curve, so the engine parameter for it is deliberately empty rather than set to a plausible-looking figure, and the honest output is “at least this much”. Size up from it. engine parameter solar.power_derate_factor · engine_default

  • Why the storage figure is “delivered”, not “nameplate”

    What reaches your appliance is the battery's nameplate capacity times the depth of discharge the pack allows times the inverter's efficiency. Only 6 of the 29 station records in this library publish enough to derive that figure, and 0 of the 6 products this page can recommend do — which is a fact about the balcony-storage category, not about our research. Where it is missing, the card says so rather than comparing your target against a nameplate that means something else.

  • The sunlight band is an input, not a source

    Every other number on this page traces to a manufacturer document with a verification date. The peak-sun-hours band does not: WattPair holds no irradiance dataset, so rather than dress a made-up figure in a source label, the bands are declared as this tool's own conservative enumeration, sizing uses the bottom of whichever you pick, and the two public tools that will give you a real figure for your own address are linked next to the control. If your band is wrong, the array figure is wrong in proportion, and nothing else on the page moves.

  • And what a product costs to just be switched on

    A storage product spends energy doing nothing — the compatibility engine puts that term in the denominator when it computes a runtime, because the manufacturer's own formula does. It is not in the sizing arithmetic above, which is a load-side figure, so treat the storage number as covering your appliances and not the box's own overhead. engine parameter compat.include_station_idle_draw · appliance_evidence

How these numbers are graded

Every appliance and product field carries a source tier, a source URL, a verification date and a confidence grade, and a conclusion inherits the weakest of them — the grades are a minimum, never an average. A figure computed from a manufacturer's own coefficients stays official but is capped at medium confidence and labelled as derived.

Coverage today, read from the library at build time rather than claimed: 30 appliance profiles; 29 station records, of which 3 are balcony/plug-in storage products and 3 more are selected for off-grid use — the 6 this page recommends from; 3 of 5 panel records can support the array check. No lab measurement exists in the library yet; when one does it will be labelled as such, and nothing on this site claims one before then.

Two things on this page are deliberately absent. There is no cost, payback, rebate or incentive figure, because those change faster than a page can be revised and a stale one is worse than none — the principles and where to check belong in the Knowledge channel with a verification date on them. And there is no derate factor applied to the array, because this site has measured none; the number you get is a floor and says so.

Questions people actually ask

How many solar panels do I need to power my house?
Panels are the wrong unit — a "panel" is anything from 100 W to 550 W, so the answer to that question is a number of watts, not a number of objects. Start from the list of things you actually want to keep running: on the worked example above, a fridge, the internet and six lights come to 1,595 watt-hours a day, which needs at least 0.5 kW of array at the sunlight band selected. Then decide how many panels that is, based on the panels you can physically fit. What this page will not do is size a whole-home grid-tied system for you — that needs a load study, a roof, and a licensed installer, and picking one of those is not something this site does.
How much battery do I need for a solar setup?
Enough to carry the load through the hours the sun is not doing it, which is the daily energy multiplied by the days of autonomy you want. On the worked example that is 1.6 kWh at one day of autonomy — and that is kilowatt-hours delivered at the socket, not the number printed on a battery. The two are not the same: usable energy is nameplate capacity times depth of discharge times inverter efficiency, and 23 of the 29 records in this library publish nothing that would let anyone derive it.
Is a balcony solar system enough to run my fridge?
On the numbers above, the daily energy of a full-size refrigerator is well inside what a balcony array produces on an average day. The catch is not energy, it is legality and geometry: whether plug-in solar is permitted where you live, whether your balcony faces anywhere useful, and whether the product is even sold in your state. One of the products this page can recommend is restricted to a single US state by law, and that restriction is printed on its card rather than hidden in a footnote. The electrical question is the one this calculator answers; the legal one has its own guide.
Why does this page not tell me what it will cost or what I will save?
Because any number in that shape would be a guess dressed as a fact. Payback depends on your electricity tariff, your consumption profile, your local incentives and how those incentives change — and incentive law in this area moves month to month. WattPair states principles and where to check, never an amount, and it carries no cost, rebate or payback figure anywhere. What it will tell you is exactly how much energy your list needs and exactly how big an array and a battery have to be to supply it. Those two numbers are the ones that do not change when the policy does.
Does this recommend an installer?
No, and it never will. This site sizes systems and points at products you can buy directly; installer matching is not something it does, and there is no form on this page, no email capture and nothing that collects anything about you. For a whole-home grid-tied system the numbers above are a starting point for a conversation with a licensed professional, not a substitute for one — a real design also needs a roof survey, a service-panel assessment and a permit, none of which a calculator can see.
Why is the suggested array bigger than the daily energy divided by the sun hours?
It is not — it is exactly that, and that is the problem. The figure this page gives is a floor computed at standard test conditions: full sun on a clean, cool, perfectly-angled panel. A real array loses output to heat, dust, angle and cloud, and WattPair publishes no derate factor because it has measured none. Every other calculator multiplies by something like 0.75 at this point; this one tells you the multiplication is missing instead of inventing the multiplier. Size up from this number, do not size down to it.
Once you have the kit

This page sizes the array. Before you buy panels, make sure the ones you pick are electrically legal on the input you are plugging them into — check the array against the input

The other direction

If the question is “how long will what I already own last”, rather than “how big should it be”, that is the runtime calculator

Covered · 0.5 kW EcoFlow STREAM Ultra

US-UT only · no button