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To produce 1,000 kWh per month you need about 9.3 kW of solar at 4.5 peak sun hours, which is 24 panels of 400 W. In sunnier places it drops to around 7 kW; in cloudy northern climates it rises above 11 kW.
Solar size from your electricity bill
Estimates use the formulas explained in this guide. Plan a complete system with the all-in-one calculator →
The calculation
- Convert monthly to daily: 1,000 kWh ÷ 30 = 33.3 kWh per day = 33,333 Wh.
- Divide by peak sun hours × 0.80: at 4.5 sun hours, 33,333 ÷ 3.6 = 9,259 W.
- Divide by panel wattage: 9,259 ÷ 400 = 23.1, rounded up to 24 panels.
Panels needed for 1,000 kWh/month by location
| Peak sun hours | Array size | 300 W panels | 400 W panels | 450 W panels |
|---|---|---|---|---|
| 3.0 (UK, Pacific Northwest) | 13.9 kW | 47 | 35 | 31 |
| 4.0 (Northeast US) | 10.4 kW | 35 | 27 | 24 |
| 4.5 (much of the US) | 9.3 kW | 31 | 24 | 21 |
| 5.0 (Texas, Florida) | 8.3 kW | 28 | 21 | 19 |
| 6.0 (Arizona) | 6.9 kW | 24 | 18 | 16 |
Should you size for 100%?
For grid-tied homes, how much of your 1,000 kWh to offset depends on your utility’s rules:
- Full retail net metering: sizing close to 100% usually gives the best return, because excess daytime power earns credit at the same rate you pay.
- Net billing or low export rates (such as California’s NEM 3.0): exported power is worth much less. Sizing to cover your daytime use, or adding a battery, often makes more sense than a large array.
- No net metering: size to what you use in real time, or plan for storage.
Does 1,000 kWh per month need batteries?
Not for a grid-tied system. If you want backup during outages, add storage sized for your essential loads, not your whole 33 kWh day. A typical backup battery of 10 to 15 kWh covers a refrigerator, lights, internet and a well pump overnight. See home battery backup size.
For a fully off-grid home using 1,000 kWh per month, you would need roughly 33 kWh of usable storage per day of autonomy, which is a large and expensive bank. Reducing consumption first almost always pays off.
Roof space for a 9.3 kW system
At about 21 square feet per 400 W panel, 24 panels need around 500 square feet of unshaded roof plus setbacks. If your roof is smaller, choose higher-efficiency panels or consider a ground mount. Our roof space guide shows the math.
Ways to cut the system size
- Swap an old refrigerator or freezer: modern ENERGY STAR models can use less than half as much.
- Move to a heat pump water heater, which uses roughly a third of the electricity of a standard electric tank.
- Seal air leaks and improve attic insulation to reduce air conditioning load.
Every 100 kWh per month you save removes about 2 to 3 panels from the design.
Use the solar calculator with your own daily kWh (monthly ÷ 30) to get your array, inverter and battery sizes in one go.
Worked example: 1,000 kWh in two very different homes
Home A, Florida (5.0 sun hours), net metering, no battery:
- Array: 33,333 ÷ (5.0 × 0.80) = 8.3 kW, so 21 × 400 W
- Inverter: string inverter around 7 to 7.6 kW AC (a DC/AC ratio of about 1.1 to 1.2)
- Roof: about 480 sq ft including spacing
Home B, Brisbane (5.3 sun hours), feed-in tariff, frequent summer storm outages:
- Array: 33,333 ÷ (5.3 × 0.80) = 7.9 kW, so 18 × 440 W (7.92 kW)
- Inverter: hybrid 8 to 10 kW to run split-system ACs during the day and keep power during outages
- Battery: 10 to 15 kWh of LiFePO4 for evening and outage coverage
The panel count is similar; the equipment around it differs because of grid reliability.
Monthly production vs consumption
Even a perfectly sized system won’t match your bill every month. An 8.3 kW system in a mid-latitude location might produce:
| Month | Typical production | Typical household use |
|---|---|---|
| January | 650 kWh | 950 kWh (heating) |
| April | 1,050 kWh | 750 kWh |
| July | 1,150 kWh | 1,350 kWh (cooling) |
| October | 900 kWh | 800 kWh |
Over the year it balances to about 12,000 kWh, but individual months over- or under-produce. Net metering or annual credit rollover makes this work.
Steps to size your own 1,000 kWh system
- Add up 12 months of bills and divide by 365 for daily kWh.
- Look up your peak sun hours for your roof’s tilt and direction.
- Array watts = daily Wh ÷ (sun hours × 0.80).
- Choose a panel wattage and round up the count.
- Check roof fit and shading.
- Choose inverter type (string, micro, hybrid) based on shading and backup needs.
Common mistakes
- Sizing on one high summer bill, which oversizes the system.
- Ignoring future loads such as an EV or heat pump; leave room to add panels.
- Forgetting export limits. Some utilities cap system size relative to your sanctioned load or past usage.
Panel counts by panel size (4.5 sun hours, 9.3 kW)
| Panel | Panels for 1,000 kWh/month |
|---|---|
| 330 W | 29 |
| 400 W | 24 |
| 450 W | 21 |
| 550 W | 17 |
| 600 W | 16 |
Fewer, larger panels mean less racking and fewer connections, but check that they fit your roof layout and racking.
FAQ
How many solar panels for 2,000 kWh per month?
Double the figures above: about 18.5 kW, or 47 panels of 400 W, at 4.5 peak sun hours.
How many panels do I need for 500 kWh per month?
Half the figures: about 4.6 kW, or 12 panels of 400 W, at 4.5 peak sun hours.
Does inverter size affect production?
Grid-tied inverters are often sized at 80 to 90% of array wattage, which is normal and loses very little energy. See what size inverter do I need.
How many kW is needed for 1,000 kWh per month?
About 7 to 8.5 kW in sunny regions and 9 to 11 kW in moderately sunny ones; a “unit” is 1 kWh.
How many batteries for 1,000 kWh per month?
For backup only, 10 to 15 kWh covers essentials overnight. Running the whole home off-grid would need about 39 kWh of LiFePO4 per day of autonomy.
Related guides
- What Size Solar System Do I Need for 30 kWh Per Day?
- How Many Solar Panels Do I Need? (Step-by-Step Calculator Method)
- What Can a 1kW Solar System Run? kWh per Day for Cabins, RVs, Sheds and Backup
- What Can a 10kW Solar System Run? kWh per Day, Central AC, EV and Whole-Home Loads
Sources and further reading
- U.S. EIA: How Much Electricity Does an American Home Use?: average household use, about 10,800 kWh a year.
- NREL PVWatts Calculator: solar output estimate for any address.
- European Commission JRC: PVGIS: free solar output and optimum-tilt tool for Europe and most of the world.
- Global Solar Atlas (World Bank): sun data and solar potential for any location.