Three findings
- Output changes almost 5×. In Hartford, a north-facing railing makes about 220 kWh a year; a south-facing patio makes about 1,040 kWh.
- Savings change far less: about 2× ($63 vs $138 a year). With no credit for power sent to the grid, what you save is capped by what your home uses while the sun is up. A 150 W always-on load only soaks up so much, so extra output mostly flows to the grid.
- Your electricity rate matters as much as your sunshine. A south-facing railing in Hartford ($116 a year at 29.2¢) saves more than a south-facing patio in sunnier Denver ($84 a year at 16.1¢).
Every direction, on a railing and on a patio
Hartford, CT, Connecticut Light & Power Co at 29.2¢ per kWh, 800 W kit. A railing or fence holds the panels upright (90°); a patio or yard stand tilts them back to about 30°.
Railing or fence, 90°
Patio or yard, 30°
Hartford: 800 W kit, a year's output and savings by direction
| Facing | Railing or fence, 90° | Patio or yard, 30° | ||||||
|---|---|---|---|---|---|---|---|---|
| Made | Used at home | % used | Saved / yr | Made | Used at home | % used | Saved / yr | |
| North | 220 kWh | 220 kWh | 99% | $63 | 560 kWh | 390 kWh | 69% | $113 |
| North-east | 330 kWh | 270 kWh | 83% | $79 | 640 kWh | 400 kWh | 62% | $118 |
| East | 520 kWh | 330 kWh | 63% | $96 | 820 kWh | 430 kWh | 52% | $125 |
| South-east | 660 kWh | 370 kWh | 56% | $108 | 970 kWh | 450 kWh | 47% | $133 |
| South | 710 kWh | 400 kWh | 55% | $116 | 1,040 kWh | 470 kWh | 45% | $138 |
| South-west | 670 kWh | 380 kWh | 56% | $110 | 970 kWh | 460 kWh | 47% | $134 |
| West | 510 kWh | 330 kWh | 65% | $97 | 810 kWh | 430 kWh | 53% | $126 |
| North-west | 310 kWh | 270 kWh | 86% | $79 | 640 kWh | 400 kWh | 63% | $117 |
Flat roof or shed, south at 10°: 960 kWh made, 480 kWh used at home (49%), $139 a year.
Why making more doesn't mean saving more
A kit only saves money on power your home uses at the moment the panels make it. Our model assumes a steady always-on load (fridge, router, standby devices) of 150 W. On a sunny afternoon an 800 W kit makes several times that, and the rest goes to the grid. That is why a north-facing railing uses 99% of its small output while a south-facing patio uses only 45% of its large one.
So the always-on load moves savings more than the last few degrees of direction do. With a 100 W load, the Hartford patio uses 33% of what it makes; with 300 W, 75%, and savings go from $99 to $227 a year.
Hartford, south-facing 800 W kit: what the always-on load changes
| Always-on load | Railing or fence, 90° | Patio or yard, 30° | ||||
|---|---|---|---|---|---|---|
| Used at home | % used | Saved / yr | Used at home | % used | Saved / yr | |
| 100 W | 290 kWh | 41% | $86 | 340 kWh | 33% | $99 |
| 150 W (our default) | 400 kWh | 55% | $116 | 470 kWh | 45% | $138 |
| 300 W | 590 kWh | 83% | $172 | 780 kWh | 75% | $227 |
You can see this hour by hour on the sunny-day chart on any result page: the highlighted area is what the panels make, the blue area is what your home uses.
Power sent to the grid earns nothing here. Every state law where we've read the export rules (New Hampshire, New Jersey, Utah, Vermont and Virginia) says these kits get no net metering or no payment for export. Connecticut's law goes further: the device must warn that power sent out can be billed as usage on a meter without net metering. See every state's law.
Four cities, four rates
800 W kit: made and saved per year, by city and placement
| City | Rate used | South railing 90° | West railing 90° | North railing 90° | South patio 30° |
|---|---|---|---|---|---|
| Hartford, CT | 29.2¢OpenEI: Connecticut Light & Power Co | 710 kWh$116 / yr | 510 kWh$97 / yr | 220 kWh$63 / yr | 1,040 kWh$138 / yr |
| Salt Lake City, UT | 12.3¢OpenEI: PacifiCorp | 800 kWh$53 / yr | 590 kWh$44 / yr | 240 kWh$29 / yr | 1,220 kWh$62 / yr |
| Denver, CO | 16.1¢OpenEI: Public Service Co of Colorado | 890 kWh$72 / yr | 590 kWh$59 / yr | 240 kWh$38 / yr | 1,320 kWh$84 / yr |
| Richmond, VA | 16.2¢OpenEI: Virginia Electric & Power Co | 700 kWh$65 / yr | 510 kWh$54 / yr | 210 kWh$34 / yr | 1,100 kWh$79 / yr |
Denver's south-facing patio makes 27% more than Hartford's, but saves $84 a year against $138, because power in Hartford costs 29.2¢ per kWh and in Denver 16.1¢.
What to do with this
- South, south-east or south-west is best. East and west lose 21–29% of the output of south in Hartford (patio: east 820 kWh vs south 1,040 kWh) but only 9–17% of the savings.
- A north-facing railing makes little. In Salt Lake City, where power costs 12.3¢, it saves about $29 a year: a $500 kit would pay back in 17.1 years, a $1,500 kit in more than 25 years. In Hartford, the same railing takes 7.9 to 23.7 years.
- If your home uses little during the day, a smaller kit can pay back faster. A 400 W kit on the same south-facing Hartford railing makes about 360 kWh, of which you'd use 82%: about $87 a year, against $116 for 800 W. Half the panels keep 75% of the savings, so the smaller kit pays back sooner if it costs less than 75% of the bigger one's price.
- Follow your kit's mounting instructions and your state's rules. Vermont requires the kit to be connected to a smart meter. Virginia requires telling your utility on the state form before you install. We don't give installation advice beyond that.
Your balcony, your rate
Your address, the way your panels face, their tilt and your utility's rate.
Limits of this model
- Shade from balconies above, walls and trees isn't modeled beyond the losses setting (14% here).
- Weather is one typical year, not any particular year.
- An hourly model averages out short spikes in use, so real self-use can differ a little either way.
- The flat 150 W always-on load is an assumption. A meter file from your utility replaces it on your result.
- Rates change. These are the rates our lookup returned on Sep 29, 2026.
Method and sources
Modeled on Sep 29, 2026: 800 W kit, 800 W inverter limit, 14% losses, 150 W always-on load, no export credit.
- Solar output: NLR PVWatts v8, hourly, typical-year weather from the National Solar Radiation Database, clipped at the inverter limit each hour.
- Rates: the utility's residential tariff from the OpenEI Utility Rate Database, or the state's average from the EIA when there's no usable tariff. Each city's source is in the table above.
- Every figure is the same calculation as a result page; the 400 W figure is that page's "Go smaller" comparison. Full method: how we calculate.
- Independent check: we ran the same points, kit size and losses through PVGIS, the European Commission's solar model, using its US satellite data (PVGIS-NSRDB). Its yearly output for every south-facing railing and patio below is within 8% of ours. In Hartford, PVGIS puts a vertical south-facing kit at 69% of the 30° patio; our model says 69%.
Yearly output, south-facing 800 W kit: our model vs PVGIS
| City | Railing 90° | Patio 30° | ||
|---|---|---|---|---|
| Ours | PVGIS | Ours | PVGIS | |
| Hartford, CT | 710 kWh | 730 kWh | 1,040 kWh | 1,050 kWh |
| Salt Lake City, UT | 800 kWh | 800 kWh | 1,220 kWh | 1,220 kWh |
| Denver, CO | 890 kWh | 890 kWh | 1,320 kWh | 1,300 kWh |
| Richmond, VA | 700 kWh | 750 kWh | 1,100 kWh | 1,140 kWh |
General information, not financial or electrical advice.