Kiwi homes are notoriously under-insulated and often heating is inefficient and expensive. If you want to warm things up first look to insulate thoroughly before thinking through your options for heating. If you house is damp you might want to consider a ventilation system. If you want a cheap power bill then consider an efficient heat pump! Also take a moment to look at subsidy options your local council may be running for various clean heat options!
Specify and click Calculate on the right to refresh the estimate.
Now you have an idea of costs, post a real job, to get a real quote and find a tradesperson do the work!