Why start here?

Before you price solar panels, you get the biggest bang for your buck by trimming the watts you already use. As the open textbook To Catch the Sun explains in its energy-audit chapter (pp. 150-158), every watt you don't need today is one you don't have to pay to generate tomorrow.

A smaller demand means a smaller solar array, a smaller inverter and a smaller battery, which means a lower upfront cost.

The three-step process

List every electrical appliance in your house. Walk through room by room. Don't forget hidden loads like routers, heated towel rails and the hot water cylinder.
Write down each appliance's power and daily hours of use. Look for the rating label; if it is missing, use the typical figure in the table below. Multiply watts ÷ 1,000 × hours to get daily kWh, then add them up. That is your estimated daily demand.
Cut demand, then re-total. Highlight the energy hogs and note ways to reduce or shift their use. Re-run the numbers after the changes. The efficient total is your target for sizing solar.

Home appliance load table

Typical New Zealand figures. Real power varies by brand, model and mode, so use the label or a plug-in power meter wherever you can.

Appliance	Typical power (W)	Typical use (hours/day)	Daily kWh
Fridge-freezer	100-150 when running	runs on and off all day	1.0-1.5
Electric kettle	2,000-2,400	0.2	0.4-0.5
Oven	2,000-3,500	0.5	1.0-1.75
Induction cooktop (per element)	1,400-3,700	0.5	0.7-1.85
Microwave	800-1,200	0.2	0.16-0.24
Dishwasher (eco cycle)	1,200-2,400	1	0.8-1.5
Washing machine (cold wash)	300-500	1	0.3-0.5
Clothes dryer (vented)	2,000-3,000	1	2-3
Heat pump (heating, running)	600-2,500	6	4-12
Hot water cylinder element	2,000-3,000	2-3	4-9
Hot water heat pump	500-1,000	3-4	1.5-4
Heated towel rail	60-150	24 if left on	1.4-3.6
LED light (each)	5-10	5	0.03-0.05
Television	50-150	4	0.2-0.6
Computer or laptop	30-150	4	0.1-0.6
Wi-fi router	8-15	24	0.2-0.36
EV charging from a standard plug	about 2,300	depends on driving	about 2.3 per hour

How to read a label: if it gives amps (A) instead of watts (W), multiply by 230 volts. A 10 A appliance draws about 2,300 W.

Step by step

List and label. Use the table as a worksheet.
Find the wattage. Check the appliance label first. If it quotes amps, multiply amps × 230 V.
Calculate daily energy. Daily kWh = (W ÷ 1,000) × hours. Log actual run-time for a week if you can; smart plugs make this easy.
Reduce before you produce. Swap halogens for LEDs, fix fridge seals, run the dishwasher on eco, put the towel rail on a timer. Behaviour and efficiency often trim 15-40% of demand.
Re-total and map to solar. With your efficient daily kWh, chapter 7 of To Catch the Sun shows how to size panels and batteries (pp. 158-165), and the economics of sizing (pp. 174-176).

Why demand reduction comes first

"A dollar spent on efficiency can save five on generation." To Catch the Sun, p. 158

That means you can:

buy fewer or smaller solar panels to meet your needs;
shrink the inverter and battery, which drives down cost;
leave headroom for EV charging or a hot water heat pump later.

What the Southland numbers say

Rewiring Aotearoa's Electrifying Southland report finds a 9 kW solar and 10 kWh battery system saves a Southland home about $2,500 a year on power bills, with financed solar working out at about 12c/kWh against roughly 26c/kWh from the grid. Electrifying heating, hot water, cooking and two cars as well takes the average Southland home's energy bills from about $12,420 to $4,710 a year.

Next steps and further reading

Rewiring Aotearoa home electrification guide: step-by-step upgrades, machine by machine.
Rewiring household calculator: your own savings estimate.
To Catch the Sun (free web edition): load assessment (pp. 150-158), panel sizing (pp. 158-163) and economic sizing (pp. 174-176).

Home Electrification Guide