Just used the compressor as an example of trying to come up with solutions for removing unnecessary electrical loads. The use of cordless tools is an example and then charge those at night. Then again, a tool charger doesn`t take much energy...but every little bit counts.
That is the sort of heater that would work or you could get one of the bullet-shaped construction heaters that would be lower and more stable; they even have some on wheels. I`d worry the one you linked might fall over and hit the tent and it would burn a hole in your tent in a second. Pay attention to the BTUs and you may need to do some research to find out how many BTUs you`ll need to heat the tent when you`re washing a car when it gets really cold out. You`ll also need a big enough tent to make sure the heater isn`t too close to the tent or it will melt and if too close to the vehicle, it could also damage the paint.
Figure out the number of items you`ll need on the generator and are using at the same time. And then focus on the set of equipment that takes the most power. As an example, I see the tent fan, vacuum, and carpet shampooer as two concurrent options. Size for the largest set that you`ll be using at the same time.
Option 1:
* Tent fan - 600w ???
* Vacuum - 1000w ???
Option 2:
* Tent fan - 600w ???
* Carpet shampooer - 1200w ???
In the example above, one assumption I`m making is that you will NOT run the vacuum and the shampooer at the same time. If that is true, for my fictional example, you`d use option 2 to size your generator since it is the largest power using set of equipment you`ll run at the same time. And then you`d use that max power set to size your generator. In this case you`d need 1800w continuous power but you can`t buy an 1800w generator or even a 2000w generator. You`ll probably want/need at least 30-40% additional power to give the generator head-room and to allow for additional power motors require upon startup. Your generator won`t last long if constantly running at full output.
One other thought. Will you really need a shampoo machine? Could you come up with another workflow that gives as good results without the need for another piece of equipment? I studied engineering in school and engineering is about building something efficiently. Many engineers can build a bridge that is incredibly strong and expensive but the difficulty is in building something strong enough while minimizing costs. As a professional detailer, you need to dial in your processes to minimize time and improve results. If a piece of equipment will make a huge difference for your customers and your bottom line, then include it. But you really need to look at every single piece of equipment to validate it is absolutely needed. This makes sense from an initial investment standpoint as well as long term return.
