Something to consider.

I got a quote from my supplier, put a small markup and sent it to the customer.

The customer calls and tells me that they can purchase the inverter R2000 cheaper directly from my supplier.

What do you think I replied - yip you are correct, then go buy it and I will install it.

Every one is happy, I get the job and make money on the other materials that I supply at a better markup.

Until something goes wrong, that is where it gets interesting, now the supplier has to get people out to site to check the unit, if it is faulty, they have to remove it, repair it and replace it.

The supplier must now deal directly with the customer and all warranty claims technical queries etc.

So in the long run, you as the installer are better off, because you dont have to worry about backup service, your turnover doesn't go crazy in the millions, so you dont have to register with vat,

and in 8 years time (if you are still around) you dont have to worry about warranty claims.

Let the suppliers sell the product directly to the customer, let them deal with customer when the batteries start failing or the software has to be upgraded (that happens a lot with certain batteries), when firmware upgrades are required.

Is a win win for the installer, I talk from years of experience dealing with customers and suppliers, the suppliers are quick to tell you they dont do technical, then they shouldn't compete with the installers.