Solar panels and panel brands

How Much Energy Does a 1-Watt Solar Panel Make on a Winter Day?

Published · By the SolarPanelX editors · Prices and specs as of that date, from the pages under Sources

Summary

By Voltaic Systems' figures, a 1 W panel tilted at 45 degrees makes 3.6 Wh a day in New York in June and 2.1 Wh in December. Seattle's December figure is 1.1 Wh. Voltaic assumes about half of that is lost going into a lithium battery and back out, so the device sees roughly half.

June against December

LocationJune, per dayDecember, per day
New York3.6 Wh2.1 Wh
Seattle3.5 Wh1.1 Wh
Stockholm3.8 Wh0.8 Wh
Nairobi2.6 Wh4.2 Wh

The table is Voltaic's, for a 1 W panel at 45 degrees. The four cities are close in June and far apart in December, and Voltaic's own comment on the table is that the numbers are often less than people expect, especially in winter.

A 0.5 W sensor running around the clock uses 12 Wh a day. If about 1 Wh per panel watt reaches it on a New York December day (half of 2.1), the panel has to be rated around 11 W. In Seattle the same month, it is around 22 W. Voltaic suggests a battery that can carry the system for at least five days on its own, which for this sensor is 60 Wh.

What "6 V" means on a small panel

ModelPeak powerOpen-circuit voltagePeak voltageSizeWeightPrice
P124 (1.2W 6V)1.35 W7.28 V6.23 V66 x 113 mm31.6 g$14
P126 (2W 6V)2.62 W8.74 V7.48 V112 x 136 mm79 g$21
P105 (5W 6V)5.75 W7.13 V6.12 V148 x 223 mm188 g$35

All three product pages list IP67 waterproofing and a two-year warranty. Voltaic rates its ETFE-coated panels at five to seven years of outdoor life.

Voltaic says a panel attached to a battery drops to a voltage set by the battery's charge circuit, and it advises choosing a panel voltage above the battery's charge voltage. In its example, a 6 W panel with a 6.2 V peak voltage drops to 5.1 V once connected to a battery, and the charge circuit steps that down to cell voltage. Each of the three pages above says the panel will charge a single-cell lithium-ion battery.

Sources

  1. Voltaic Systems — Small Solar Panels
  2. Voltaic Systems — 1.2 Watt 6 Volt Solar Panel (ETFE)
  3. Voltaic Systems — 2 Watt 6 Volt Solar Panel (P126)
  4. Voltaic Systems — 5 Watt 6 Volt Solar Panel (ETFE)
  5. Voltaic Systems — Remote Power Systems for IoT
  6. Voltaic Systems Blog — Measure the Daily Power Consumption of Your IoT Device (2018-11-19)
  7. Voltaic Systems Blog — Estimate an IoT Device's Solar Irradiance (2018-06-05)

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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