RV ELECTRICAL LOAD CALCULATOR


Calculator provides an estimate of AC and DC load usage and potential solar gain for an off-grid RV or travel trailer. Output helps determine battery AHr and solar needs
Calculator provides an estimate of AC and DC load usage and potential solar gain.

Instructions

Start by inputing DC losses in Section 1, these are the basic loads that will be drawn from the battery.

If you will not use an Inverter (to produce AC power for TV's and microwave or air conditioner) there is no need to fill out Sections 2. If you will be using an inverter, complete Section 2.

After you have input the losses, select your location in Section 3 and enter the number of solar panels and a solar gain value will be calculated.

Section 4 provides a summary of losses and gains and some suggestions.

Section 1 - DC Losses due to 12VDC Users
User
Wifi router
Cellular router
Cellular booster
Fridge (12V / propane)
Water heater (12V / propane)
Furnace (7.5A / 25,000 BTU)
Inverter Charger (Idle)
h/day
Ah/day
.00
[cb-wifi]*[hrs-wifi]
.00
[cb-cr]*[hrs-cr]
.00
[cb-cb]*[hrs-cb]
.00
[cb-fr]*[hrs-fr]
.00
[cb-wh]*[hrs-wh]
.00
[cb-fur]*[hrs-fur]
.00
[cb-inv-stdby]*[hrs-inv-stdby]

Notes: - Select applicable users for your application using the checkboxes on the left. Select the number of hours per day that the load will operate. Loads that are on all the time should be set at 24hrs. The consumed Ahr for each load is shown in the last column.


0
.00
[cb-wifi]*[hrs-wifi]+[cb-cr]*[hrs-cr]+[cb-cb]*[hrs-cb]+[cb-fr]*[hrs-fr]+[cb-wh]*[hrs-wh]+[cb-fur]*[hrs-fur]+[cb-inv-stdby]*[hrs-inv-stdby]+[cb-oth]

Notes: - Use the slider to fine tune Ahr total to suit you application.

Section 2 - DC Losses due to 120VAC Users
User
Inverter (inverting - zero load)
LCD TV
Bluray / DVD player
Microwave (1200W)
Coffee maker (600W)
Fridge (AC / 600W)
Air Conditioner (13,000 BTU)
Air Conditioner (15,000 BTU)
h/day
Ah/day
.00
[cb-inv-zero]*[hrs-inv-zero]
.00
[cb-tv]*[hrs-tv]
.00
[cb-blr]*[hrs-blr]
.00
[cb-mw]*[hrs-mw]
.00
[cb-cm]*[hrs-cm]
.00
[cb-fr-ac]*[hrs-fr-ac]
.00
[cb-ac13]*[hrs-ac13]
.00
[cb-ac15]*[hrs-ac15]

Notes: - Select applicable users for your application using the checkboxes on the left. Select the number of hours per day that the load will operate. Loads that are on all the time should be set at 24hrs. The consumed Ahr for each load is shown in the last column.


User
Smart Phone (full charge)
Tablet (full charge)
Laptop (full charge)
Charges/day
Ah/day
.00
[cb-sp]*[hrs-sp]
.00
[cb-tab]*[hrs-tab]
.00
[cb-lap]*[hrs-lap]

Notes: - Select applicable devices that will need to be charged. For these items, select the number of full charges required for each in the second column. e.g. if there are 2 smartphone to be charged each day select 2.

0
.00
[cb-inv-zero]*[hrs-inv-zero]+[cb-tv]*[hrs-tv]+[cb-blr]*[hrs-blr]+[cb-mw]*[hrs-mw]+[cb-cm]*[hrs-cm]+[cb-fr-ac]*[hrs-fr-ac]+[cb-sp]*[hrs-sp]+[cb-tab]*[hrs-tab]+[cb-lap]*[hrs-lap]+ [cb-ac13]*[hrs-ac13]+[cb-ac15]*[hrs-ac15]+[cb-oth-ac]

Notes: - Use the slider to fine tune Ahr total to suit you application.

Section 3 - Solar Gain
Average Summer Hours of Full Sun per day by Location
.00 hrs
[sel-loc]

Notes: - Select location where the RV or travel trailer will be located. The average summer hours of full sun will be shown. This is used to calculate potential summer solar gain / day belowr.

RV Length / Max Number of Solar Panels
panels
[rv-length]*1

Notes: - Select the length of your RV to see a typical maximum number of solar panels that can be installed.


# Solar Panels Installed and Potential Solar gain / day
kWh
([no-sopa]*[sel-loc]*100)/1000
Ahr (@12.8VDC)
(([no-sopa]*[sel-loc]*100))/12.8

Notes: - Select the number of solar panels installed on the left. The potential kWh produced per day by the solar panels will be calculated based on full sun for the location selected above. This value is converted to battery Ahr at a nominal 12.8V battery voltage to show potential battery capacity that could be replaced by the solar panels per day. This calculation is an estimate only and not a guaranteed value and should be used for general guidance only. Real world experience shows that the values calculated are somewhat conservative for a full day of sun with no shading. The Boundless solar array which has 6 x 100W panels located in Ohio will often deliver in excess of 4kWh of solar gain during a full sun summer day.

Section 4 - The Balance Sheet - Losses, Gains and Suggestions

Section 1 - DC Losses due to 12VDC Users

Section 2 - DC Losses due to 120VAC Users

Total DC Losses
Section 3 - Solar Gain
Net Gain / Loss
Ahr
[cb-wifi]*[hrs-wifi]+[cb-cr]*[hrs-cr]+[cb-cb]*[hrs-cb]+[cb-fr]*[hrs-fr]+[cb-wh]*[hrs-wh]+[cb-fur]*[hrs-fur]+[cb-inv-stdby]*[hrs-inv-stdby]+[cb-oth]
Ahr
[cb-inv-zero]*[hrs-inv-zero]+[cb-tv]*[hrs-tv]+[cb-blr]*[hrs-blr]+[cb-mw]*[hrs-mw]+[cb-cm]*[hrs-cm]+[cb-fr-ac]*[hrs-fr-ac]+[cb-sp]*[hrs-sp]+[cb-tab]*[hrs-tab]+[cb-lap]*[hrs-lap]+ [cb-ac13]*[hrs-ac13]+[cb-ac15]*[hrs-ac15]+[cb-oth-ac]
Ahr
[cb-wifi]*[hrs-wifi]+[cb-cr]*[hrs-cr]+[cb-cb]*[hrs-cb]+[cb-fr]*[hrs-fr]+[cb-wh]*[hrs-wh]+[cb-fur]*[hrs-fur]+[cb-inv-stdby]*[hrs-inv-stdby]+[cb-oth]+[cb-inv-zero]*[hrs-inv-zero]+[cb-tv]*[hrs-tv]+[cb-blr]*[hrs-blr]+[cb-mw]*[hrs-mw]+[cb-cm]*[hrs-cm]+[cb-fr-ac]*[hrs-fr-ac]+[cb-sp]*[hrs-sp]+[cb-tab]*[hrs-tab]+[cb-lap]*[hrs-lap]+ [cb-ac13]*[hrs-ac13]+[cb-ac15]*[hrs-ac15]+[cb-oth-ac]
Ahr
(([no-sopa]*[sel-loc]*100))/12.8
Ahr
(([cb-wifi]*[hrs-wifi]+[cb-cr]*[hrs-cr]+[cb-cb]*[hrs-cb]+[cb-fr]*[hrs-fr]+[cb-wh]*[hrs-wh]+[cb-fur]*[hrs-fur]+[cb-inv-stdby]*[hrs-inv-stdby]+[cb-oth]+[cb-inv-zero]*[hrs-inv-zero]+[cb-tv]*[hrs-tv]+[cb-blr]*[hrs-blr]+[cb-mw]*[hrs-mw]+[cb-cm]*[hrs-cm]+[cb-fr-ac]*[hrs-fr-ac]+[cb-sp]*[hrs-sp]+[cb-tab]*[hrs-tab]+[cb-lap]*[hrs-lap]+ [cb-ac13]*[hrs-ac13]+[cb-ac15]*[hrs-ac15]+[cb-oth-ac])*-1)+((([no-sopa]*[sel-loc]*100))/12.8)

Notes: -
1) If the projected Net Gain / Loss is negative:-
- Add more solar panels if possible and/or reduce loads.
- If AC power is required, ensure the inverter is on only when needed and turn it off when not in use. The inverter will draw power even when not driving loads. This can be simulated above by ensuring loads in Section 2 are not set at 24h/day.
- A large Ahr battery can be used to support 2-3 days or more of losses without the need for a generator or shore power connection.
- A generator can be used if the air conditioner must be operated. Note however that a generator is not normally required in cooler ambients even with other modest AC loads such as the microwave are required intermittently provided a modest solar array and a a good sized battery are installed.
- A generator is almost always needed to run the air conditioner for more than 2-3 hrs even with large batteries and solar arrays.
2) Match the Ahr capacity of the battery to the solar array so that solar energy can be fully captured each day if possible (battery should have sufficient capacity).
3) The solar array should be able to bring lead acid batteries approximately to full charge every day to maintain the batteries in good health, for lithium batteries this is not as important.


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