Refilling sounds nice. Let's look at the actual reduction in plastic and shipping weight when you switch to a glass-and-refill system.
Refillable packaging is everywhere now. It also varies wildly in how much it actually reduces waste. Here is how the math works for K.SANT.
What a refill replaces
One 16 fl oz K.SANT refill bottle becomes three 16 fl oz Every Spray bottles after dilution. So buying one refill replaces buying three new ready-to-use bottles.
If those three bottles would have been plastic spray bottles — which is the industry standard for natural cleaners — that is three plastic bottles, three trigger sprayers, and three caps that you do not buy and do not throw away.
Shipping weight
A 16 fl oz spray bottle of cleaner ships at roughly 1.3–1.4 lb door-to-door. A 16 fl oz refill ships at roughly the same weight, but it represents three bottles' worth of cleaner. So you are sending one shipment instead of three.
That is a meaningful reduction in transit emissions per ounce of cleaner delivered. Replace this paragraph with measured shipping data once the brand has 90 days of fulfillment data.
Why we still use glass for the spray bottle
It would be cheaper, and slightly lower-impact at the shipping step, to use plastic for the ready-to-use bottle. We chose glass because the bottle is the part of the system you keep. Glass on a counter is permanent. Plastic on a counter looks like a bottle that should be thrown away. Behavior follows the design.