What you will make

In this project you make an energy plan with two parts:

• A load list for winter and summer: every load, its watts and hours, and your daily kWh in each season.
• A solar and battery sizing: the array size, battery size and generator hours that would cover those loads in your climate.

The result is a planning estimate, not a design. It gives you real numbers to compare quotes and ask good questions. It saves to My plan, on this device only.

Gather your numbers

Have these ready:

• Your appliance labels, or plug-in meter readings, for the main loads (lesson 22).
• Twelve months of electric bills, if you have them (lesson 21).
• Your location, for sun hours. The free PVWatts calculator gives monthly values.
• Your climate zone, from your homestead brief.
• Which loads you could move to other fuels, or swap for efficient ones (lesson 23).

Step 1: your load list

Enter each load with its watts and hours. Do a winter list first, then a summer list. Note surge watts for pumps and other motors.

Before moving on, look at the top three loads. If one of them is heat, hot water or cooling, ask whether lesson 23 offers a cheaper swap. Changing it now shrinks everything in step 2.

Step 2: size solar and batteries

Now enter your daily kWh, your location’s sun hours, and how many days of autonomy you want. The tool estimates the array kW, the battery kWh and the generator hours for each month.

Try it two ways: once with no generator, once with a generator allowed for a few hours a month. Compare the battery and array sizes.

Winter against summer

Look at the gap between your best and worst months.

• Off grid, the array and battery are usually sized for the worst month, often December or January. In summer, the same array makes far more than you need. That extra is often wasted unless you add summer loads, such as pumping or cooling.
• Grid-tied, you can size on the yearly total. The grid absorbs summer surplus and covers winter gaps, under your utility’s rules.

In a cold, cloudy zone, the winter array can be two or three times the summer one, or more. In a sunny southern zone, the gap is smaller.

Reading your result

Check your result against a few questions:

• Does the battery cover your days of autonomy at a safe depth of discharge for its type (lesson 25)?
• Is the array in a spot with no winter shade?
• Are the generator hours ones you could live with, in noise, fuel and time?
• Does the inverter need to handle your biggest surge, such as the well pump starting?

If the numbers feel too big, go back to step 1. Efficiency changes usually cost less than more equipment.

What to take to an installer

An installer turns your plan into a real design. Bring:

• Your winter and summer load lists, with surge watts for motors.
• Your past bills or measured kWh, by month.
• Your critical loads for outages.
• Site photos: roof faces, open ground, trees and shade at different seasons.
• Your sizing result, as a starting point, not a spec.

Check

Summary and next steps

• Your load list gives winter and summer kWh per day. Big loads matter most.
• Off grid, size for the worst month. Grid-tied, size on the yearly total.
• Close the winter gap with efficiency, tilt, a bigger array or generator hours. Each has a cost.
• Your result is a planning estimate. Take it, with your load list and site photos, to a licensed installer.

Your energy plan joins your water budget in My plan. Next, the Heat track looks at the biggest load of all in cold climates.