Measuring Your Solar Needs – An Easy and Low Cost Method
While there are many posts on how to estimate your solar needs this method measures your usage using only inexpensive equipment which also has a lot of other uses.
Summary: Set up your rig with fully charged batteries to simulate a boon docking day but with power available. Use the $30 Kill-A-Watt device with adapters on the shore cord to measure your power usage for 24 hours. The watts-hours (Wh) measured would be the same as an equivalent boon docking day including DC device usage and AC device usage using an inverter.
This method then provides actual power usage which can then be used to determine the solar equipment requirement. If the usage was 1500 Wh for example then the solar could be sized to supply that power while boon docking.
Solar sizing is involved considering weather, location, mounting, time of year and other factors but at least the power usage requirements are know.
Details: The Kill-A-Watt device uses a 20A plug so you may need adapters for your rig. It’s limited to a maximum of 15A. It’s very important that your start with fully charged batteries so that you are not also measuring AC amps needed to charge the batteries. You are measuring Wh(or power) and as long as it’s equivalent to a boon docking day the Wh used are what you will need to replace in the battery.
Solar Sizing Example: For 1500Wh measured add a 500Wh margin for 2000Wh. Flat mount the panels and using 70% efficiency the solar power needed is 2000/0.7 = 2857Wh. Using 4 hours of solar yields 2857/4 = 714W. 3x 250W panels would be more than needed or perhaps compromise and install 500W.
Miscellaneous The Kill-A-Watt is a very useful device for measuring power from any plug in AC device and I highly recommend it. You can also leave it plugged in with no connected loads to monitor your rigs AC voltage. Use it in the rig or at home.
Updated to reflect Wh.
Summary: Set up your rig with fully charged batteries to simulate a boon docking day but with power available. Use the $30 Kill-A-Watt device with adapters on the shore cord to measure your power usage for 24 hours. The watts-hours (Wh) measured would be the same as an equivalent boon docking day including DC device usage and AC device usage using an inverter.
This method then provides actual power usage which can then be used to determine the solar equipment requirement. If the usage was 1500 Wh for example then the solar could be sized to supply that power while boon docking.
Solar sizing is involved considering weather, location, mounting, time of year and other factors but at least the power usage requirements are know.
Details: The Kill-A-Watt device uses a 20A plug so you may need adapters for your rig. It’s limited to a maximum of 15A. It’s very important that your start with fully charged batteries so that you are not also measuring AC amps needed to charge the batteries. You are measuring Wh(or power) and as long as it’s equivalent to a boon docking day the Wh used are what you will need to replace in the battery.
Solar Sizing Example: For 1500Wh measured add a 500Wh margin for 2000Wh. Flat mount the panels and using 70% efficiency the solar power needed is 2000/0.7 = 2857Wh. Using 4 hours of solar yields 2857/4 = 714W. 3x 250W panels would be more than needed or perhaps compromise and install 500W.
Miscellaneous The Kill-A-Watt is a very useful device for measuring power from any plug in AC device and I highly recommend it. You can also leave it plugged in with no connected loads to monitor your rigs AC voltage. Use it in the rig or at home.
Updated to reflect Wh.
