Solar Panels
Our new motorhome has a 7.0 kw generator. I imagine to run all appliances A/C, refrigerator, tv's, lights, etc. it would take much less than 7.0 kw as not everything is on at the same time. We decline...
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Assuming 2 air/con units running flat out in Arizona heat...let's say 3kw constant demand (24/7).
That means you need a total of 72kwh generated per day.
Solar panels don't generate their rated output 24/7. A good estimate is 4 times the ratted kilowatts (1000 watts) in killowatt hours. So, you are looking at around 18kw of solar panels...call it 20kw since you will lose some power converting it to battery storage and back again.
Now you need something to store those slippery electrons or they just fly away. That means a battery bank. So if we figure around 2pm, the 20kw of solar panels is putting out less than what you are using and doesn't pick up to that level again until 10am the next morning, you need to cover 20hr of use at 3kw or storage of about 60kwh.
- Traditional lead-acid batteries, you don't want to use more than 50% of the available power, so you will need around 120kwh of batteries.
- Lithium are expensive but you can use 80% without worry, so you need about 75kwh of batteries (just shy of what a Tesla has).
So now you have a way to generate power and a way to store it...but it's stored as DC power. You need a way to convert that to AC power which means an inverter. Well if it you are pulling 3000w, just get an 3000w inverter...except no, 3000w is the continuous draw once the air/con compressors are turning. To start those compressor motors takes 3-4 times the power. If you are careful (or add a device that only allows one to start up at a time, you may see 1500w + 1500w *4 or about 7500w momentarily. You need to buy an inverter that can handle a start up load of 7500w (often it's difficult to find the continous vs startup rating on inverters).
So you are looking at a very large solar array, very large battery array and a large inverter charger...realistically, it will be cheaper to maintain and fuel your existing 7kw generator. Even if you have to replace it every 8-10yrs.
That means you need a total of 72kwh generated per day.
Solar panels don't generate their rated output 24/7. A good estimate is 4 times the ratted kilowatts (1000 watts) in killowatt hours. So, you are looking at around 18kw of solar panels...call it 20kw since you will lose some power converting it to battery storage and back again.
Now you need something to store those slippery electrons or they just fly away. That means a battery bank. So if we figure around 2pm, the 20kw of solar panels is putting out less than what you are using and doesn't pick up to that level again until 10am the next morning, you need to cover 20hr of use at 3kw or storage of about 60kwh.
- Traditional lead-acid batteries, you don't want to use more than 50% of the available power, so you will need around 120kwh of batteries.
- Lithium are expensive but you can use 80% without worry, so you need about 75kwh of batteries (just shy of what a Tesla has).
So now you have a way to generate power and a way to store it...but it's stored as DC power. You need a way to convert that to AC power which means an inverter. Well if it you are pulling 3000w, just get an 3000w inverter...except no, 3000w is the continuous draw once the air/con compressors are turning. To start those compressor motors takes 3-4 times the power. If you are careful (or add a device that only allows one to start up at a time, you may see 1500w + 1500w *4 or about 7500w momentarily. You need to buy an inverter that can handle a start up load of 7500w (often it's difficult to find the continous vs startup rating on inverters).
So you are looking at a very large solar array, very large battery array and a large inverter charger...realistically, it will be cheaper to maintain and fuel your existing 7kw generator. Even if you have to replace it every 8-10yrs.
