Calculation of solar and wind generator

In a combined or as individual installations

With this guide, you can figure out how much solar and/or wind you need in a combined or individual PV or Wind installation.

It will always be your own decision about how much solar vs. wind you want/need. To help you with the decision this guide starts with the basic.

What are your power needs?

The calculation of your total power requirements is based on a review of the consumption of your electrical appliances of power (Watts) and how many hours they are running every day. Put this into the calculator. This gives you your total needs per day (in Wh and Ah).

Then select how many watts of solar you initially want to do the calculation on (can be changed on the fly!) and/or select a wind generator in the graph above the calculator. Read how much power per day (Ah/day), at a given m/s the wind generator provides. Put also this into the calculator.
Finally, you can, based on what the power needs are, see if the selected solar/wind generator combination will be sufficient.
The result will show what power you can expect to be supplied with month by month. Most all year installations need more power in winter than in summer, this is not in the calculation! This often points towards a larger wind generator. You can do two calculations one for summer and one for winter.

When you need to weigh the sun and wind against each other, be sure to think of this relation between solar power and wind generator performance over the year.
If your needs are in the summer, you should have a lot of PV and in the winter the wind generator is typically more productive.

Solar and wind generator calculator for boat, caravans cottages and offgridPower output distributed throughout the year

If you have power needs all year round, you must have a balanced power production where you primarily use solar in the summer and primarily wind generator in winter (Northern Europe).
It also means that your PV and wind generator, in theory, have a production capacity that can deliver significantly more than your daily needs, in periods of the year. However, since they produce in different periods, it is often a necessity.
Example: You need 120 Ah/day. In June/July this can be provided by 350 Watt solar panels facing south. But when there is no wind (it’s rare, but it happens), the 350 watts is required.
Unlike in December, when it would require 4200 watts of solar (it is not a calculation error! 😉 …) To provide the same 120 Ah/day. A wind generator in December makes more sense when there is more wind in the winter than in the summer months.
You, therefore, need to “over-cover” you your needs. That is having a bigger production capacity than what would be required under ideal conditions.

Solar and wind generator calculator for boat, caravans cottages and offgridThe wind is Difficult!

You need to know something about your local wind conditions. We can’t know the local conditions for your wind generator. You need to know your local wind index over a year, to get a good calculation.
You may need to google a bit to find it.
Are you going to drive/sail with your wind generator, look at this rough European map (click it to see it larger).

But no matter how you look at it, it’s hard to predict how much wind you have to produce electricity from. The graph below shows the production from Rutland wind generators from the wind that actually hits the generator blades. The statistics you can see I’m referring to here are often based on the height of XX meters and without trees and buildings that provide shelter and turbulence. That’s why you should always get a wind generator that is “too big” to cover your power needs. The best thing to do is to measure the actual wind conditions over a year, but it is rarely a practical thing to do.
A wind generator produces theoretically 8 times as much power every time the wind speed is doubled (in reality it’s a bit less). Also, therefore, it is typical in the winter a wind generator produce best since there is significantly more wind and the wind is colder. The cold wind has a higher density than hot air.

If you are sailing or live somewhere windy, it may well be that the wind generator will supply plenty of power in the summer months as well, but solar should also be considered for even at the coast there is no wind sometimes, but typically along with a high sun … .;)
On the other hand, it is typically the lowest cost in financial terms, to produce a watt-hour (Wh) by wind, then it is by solar. Simply because when there is wind enough, the wind generator will produce around the clock and solar are peaking in the middle of the day.

Conclusion: A combined installation is very often the right choice to achieve security of supply. However, it should be oversized, in both solar and wind generator sizes.

The battery must be big!

Another thing that is necessary, is a good and large battery. We refer you to our battery guide where you can read more about battery choices, but we will strongly recommend a battery that has at least 5-day needs in storage.
You will find the recommendations and minimum size for your battery in the bottom of the calculator.

Using the calculator.

The green fields in the calculator can be modified as needed. It is not certain that it is necessary, but you have the opportunity.

We need external data to show what you can expect of production in your local area. There are links to this data into the calculator and it can be a little nerdy to find the right data, but you have the possibility and can achieve a more accurate result. BUT We don’t have the data for your country pre-typed and therefore Google is your friend 🙂
IMPORTANT !!: With a calculator like this you must remember, that it is not better than the data you give it to calculate. The models are good, but if, for example. you enter an overly optimistic view of what a given wind generator can produce at your site, then the whole result will look too good and you are kidding yourself. So remember to be realistic. It can also be difficult to know which wind one can expect at a given location. The solar data are a lot more trustworthy
There are intermediate computations and results. They are probably not all so interesting for you, but they are there so you can unfold them and see them.

Whether you think this is just a calculator for your needs and master it great, or you scratch your neck and need help, you are always welcome to write or call us (+45 70 500 999). We can help you

irradiation on the solar.

In the calculator, we use a source for finding solar radiation at a particular place in Europe. The source is the European Union which publishes the data we need. You can click on the link and find the data you think suits you best. The one we have pre-typed is Aarhus, Denmark and these data can be found by plotting your location in the map and click the tab called “Monthly radiation” We use the first column “Hh” in the results you get up when you press the “Calculate “. The “Hh” column shows the result for horizontally mounted PV, as usually used on ships and caravans. The next column shows the result if you have the optimal tilt angle toward the sun (and your plant is directly south facing). In Aarhus, the optimal angle is 42 degrees. If you have a defined slope (eg. Your roofs angle) for your solar you can enter it into the calculator under “Irradiation at a chosen angle:” and you’ll get your very own customized result.
The result for the 12 separate months you can enter in the calculator and get a more accurate result.

The wind on your Wind turbine

It is somewhat difficult to find free information available online that are precise enough. The figures for wind index we have pre-typed into the calculator is the average over 10 years (2005-2015) in Denmark.

You can find wind index number for your area with a little help from Google and your local weather service. You can type the wind index directly into our calculator. Remember! That it’s only wind index figures on the distribution over a year you can change the calculator. How much your generator produces is specified from the graph of Rutland wind generators and your choice of m/s.

Solar and wind generator calculator for boat, caravans cottages and offgrid* The above graph is shown at 12 volt wind turbines. The daily production (Ah/Day) must be divided by 2 into a 24 volt plant and divided by 4 into a 48 volt plant.

Energig accept no liability for errors and omissions in calculator



Energy system Calculator
Green fields need to be changed to your data System Voltage 12 Volt
List of electricity consuming appliances.
Add electricity consumers, their wattage and hours of use per day Watt Consumption for X hours per day Consumption per day Unit
Eg. Refrigerator 65 6 390 Wh
Eg. LED light 15 5 75 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
0 Wh
Consumption per day Wh/Day 465 Wh
Consumption per day, converted to Ampere hours (Ah) 38.75 Ah
System loss / buffer 20 % 7.75 Ah
Minimum daily power generation needed. 46.5 Ah
Distribution between solar and wind turbine
How many Watt PV do you setup 100 Watt
Look at the graph above and select m/s and the turbine that fits where your turbine is mounted. 50 Ah/day
Wind Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg.
Average wind in Denmark between 2005 and 2015 (enter your own index data here) 144 108 119 89 85 74 66 73 91 99 120 134 100.2 Index tal
Din valgte vindmølle produktion vil gennemsnitligt producere: 72 54 59.5 44.5 42.5 37 33 36.5 45.5 49.5 60 67 50.0833 Ah
Sun Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg.
Average solar radiation in Denmark (Aarhus). On a horizontal surface (enter your own data here) 1180 2080 3130 3950 4400 4230 4270 4080 3330 2320 1450 1140 2963.3333 Wh/m2/day
Calculated index figures over the year. 39.8200 70.1912 105.6243 133.2958 148.4814 142.7447 144.0945 137.6828 112.3735 78.2902 48.9314 38.4702 100.0000
100 watts of panel each day produces Wh on average: 84.6385 149.1933 224.5072 283.3238 315.6012 303.4075 306.2766 292.6484 238.8527 166.4079 104.0049 81.7694 212,6 Wh
To cover with solar cells alone, you must mount: 659.2745 374.0115 248.5444 196.9478 176.8054 183.9111 182.1883 190.6725 233.6168 335.3206 536.5130 682.4069 333.3511 Watt
Daily Ah production from solar cells on average: 7.0532 12.4328 18.7089 23.6103 26.3001 25.2840 25.5230 24.3874 19.9044 13.8673 8.6671 6.8141 17.7127 Ah
Total daily production in average: 79.0532 66.4328 78.2089 68.1103 68.8001 62.2840 58.5230 60.8874 65.4044 63.3673 68.6671 73.8141 67.7961 Ah
In relation to the necessary daily production, the system delivers: 32.5532 19.9328 31.7089 21.6103 22.3001 15.7840 12.0230 14.3874 18.9044 16.8673 22.1671 27.3141 21.2961 Ah
Highly recommended battery size (Ah.) For 5 days of consumption. Bigger is better! 465 Ah
MINIMUM battery size (Ah.) For 2.5 days of consumption. 232.5 Ah