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Sizing your load: working out what your house really needs

Every honest backup quote starts with your loads, not a brochure. Here is how to do the groundwork yourself before the pilot sizing conversation.

List what must run

Walk through the house and list every appliance you would want during an outage. Note its rating from the plate, in watts or kilowatts, and whether it runs constantly, cycles, or runs in short bursts. Include things people forget: the septic pump, the water pressure pump, the gate motor, the security system and any medical equipment. Mark each as essential, useful or nice to have.

What it would keep running

Water pressure pump and septic pump
Fridge and chest freezer
Heat pump in the main room
Modem, lights and phone chargers
Medical equipment on a clinician's plan

Find your peak

Peak demand is the most power used at any one moment. Add up the kW of everything that could realistically run together, such as the heat pump, oven, kettle and pump on a winter evening. If that total is near or above 15 kW, you either stagger those loads or need a larger setup sized in the pilot.

Motors draw a short burst on start, often several times their running power. Well pumps and compressors are the ones to watch. The battery and inverter are designed to handle those bursts, but two big motors starting together is worth avoiding, and the pilot sizing will check it.

How it works →

The H2OME loop: an electrolyser splits water into hydrogen, the hydrogen is stored in a tank for weeks, a fuel cell turns it into electricity for your home, and the water returns to the loop.

Estimate daily energy

Next, estimate daily energy in kWh. Your power bill or smart meter data is the best source, since it shows real use across seasons. Then estimate the essentials-only figure by multiplying each essential load by its hours of use. That number, compared with stored energy, tells you how long backup would last. Bring both your normal and essentials-only figures to the pilot sizing.

Questions

What if my peak load is above 15 kW?

Most homes can stay under it by staggering big loads, such as not running the oven and dryer together. If your essential loads genuinely exceed it, you would need a larger or multi-unit setup sized in the pilot, or it may not be a fit.

Where do I find my daily usage?

Your power bill shows kWh used over the billing period. Many retailers also offer daily or half-hourly data online from your smart meter, which shows how use changes between seasons and days.

Should I include the hot water cylinder?

Include it, but mark it as a load to run in bursts during an outage. A full cylinder reheat is one of the biggest single energy users in many homes and can drain storage quickly.

Elsewhere

Every use →

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