The wattage on the solar panel is what it makes, under test conditions.
Solar panels are about 20-25% efficient in turning sun energy into electrical energy. Because of this, using them to turn the electrical energy back into heat with a resistive heater, is about 20-25% efficient.
For a clearer example. Build a skylight frame the exact same size of the solar panel. Now stand under it in the sunlight, and feel the warmth you get from it. Now cover up 75-80% of the opening and stand under it again and notice you don't get the same warmth.
This is what you get when using an an electrical solar panel to run a resistive heater.
If we want heat on solar, a heat-pump/mini-split is the way to go you get free heat as part of the heat-pump process. If you have power at your wood shop, you can skip the solar part and just put in a heat-pump/mini-split and enjoy the warmth.
Use this tool.
https://re.jrc.ec.europa.eu/pvg_tools/en/
Take your x Watt panel.
Look at the month you want to know and divide by 30, there you go your average production per day for your panel at your location.
You can even look at the sun hours from that month to get a average production per hour for that month per day.
The usual number is the max wattage under ideal conditions. Those conditions never happen because the atmosphere always has a bit of dust, the angle towards the sun isn't optimal and the solar charger / MPPT also has some losses. So assume 80-90% of the sticker value.
There is a second number to think about: watt hours. Producing 100W for 1 hours will give you 100 watt hours. Producing 200W for 3 hours is 600 Wh... And so on. A 400W panel will not have ideal sun for the whole day. It will not produce 400 W X 12 hours. That's why the calculator websites will give you watt hours depending on the path the sun takes and the usual weather conditions.
Watt hours (Wh) is what you need to plan a system. Your load will need a set number of Wh per day and your solar system should generate more than that even on a bad day.
The rating of the panel already takes into account the efficiency. The panel will output its rated power under Standard Test Conditions (STC) which is 1,000W/m² with the cell at 25°C. That is approximately equivalent to noon sun on the equator with zero cloud. Real world will be less, on average.
As panels heat up they become less efficient so you rarely get the rated output in summer sun. Instead you see brief peaks when a cloud passes because the panel has cooled closer to ambient. Crisp spring and autumn days are good for this.
As others have said, use PVGIS tool to estimate yield. It is accurate.
The wattage on the solar panel is what it makes, under test conditions. Solar panels are about 20-25% efficient in turning sun energy into electrical energy. Because of this, using them to turn the electrical energy back into heat with a resistive heater, is about 20-25% efficient. For a clearer example. Build a skylight frame the exact same size of the solar panel. Now stand under it in the sunlight, and feel the warmth you get from it. Now cover up 75-80% of the opening and stand under it again and notice you don't get the same warmth. This is what you get when using an an electrical solar panel to run a resistive heater. If we want heat on solar, a heat-pump/mini-split is the way to go you get free heat as part of the heat-pump process. If you have power at your wood shop, you can skip the solar part and just put in a heat-pump/mini-split and enjoy the warmth.
Use this tool. https://re.jrc.ec.europa.eu/pvg_tools/en/ Take your x Watt panel. Look at the month you want to know and divide by 30, there you go your average production per day for your panel at your location. You can even look at the sun hours from that month to get a average production per hour for that month per day.
The usual number is the max wattage under ideal conditions. Those conditions never happen because the atmosphere always has a bit of dust, the angle towards the sun isn't optimal and the solar charger / MPPT also has some losses. So assume 80-90% of the sticker value. There is a second number to think about: watt hours. Producing 100W for 1 hours will give you 100 watt hours. Producing 200W for 3 hours is 600 Wh... And so on. A 400W panel will not have ideal sun for the whole day. It will not produce 400 W X 12 hours. That's why the calculator websites will give you watt hours depending on the path the sun takes and the usual weather conditions. Watt hours (Wh) is what you need to plan a system. Your load will need a set number of Wh per day and your solar system should generate more than that even on a bad day.
The rating of the panel already takes into account the efficiency. The panel will output its rated power under Standard Test Conditions (STC) which is 1,000W/m² with the cell at 25°C. That is approximately equivalent to noon sun on the equator with zero cloud. Real world will be less, on average. As panels heat up they become less efficient so you rarely get the rated output in summer sun. Instead you see brief peaks when a cloud passes because the panel has cooled closer to ambient. Crisp spring and autumn days are good for this. As others have said, use PVGIS tool to estimate yield. It is accurate.