بهره وری اقتصادی از سیاست های آب گرم خورشیدی در نیوزیلند

New Zealand has recently followed the path of several other countries in promoting solar hot water (SHW) systems in the effort to reduce greenhouse gas emissions, yet the economic efficiency of large-scale policies to encourage SHW remains a pressing question for policymakers. This paper develops an economic framework to examine policies to promote SHW in New Zealand, including the current information, training, and subsidy policy. The economic framework points to environmental, energy security, and average-cost electricity retail pricing market failures as motivation for SHW policy, with the global climate change externality the most important of these. The results indicate that domestic SHW systems are close to being financially attractive from a consumer perspective, but a more substantial subsidy policy would be necessary for SHW to appeal to a wider audience. Such a policy is far more likely to have positive net benefits than a policy of mandating SHW on all homes or all new homes in New Zealand, and could be justified on economic efficiency grounds under reasonable assumptions. However, this result reverses under an economy-wide carbon trading system that internalizes the environmental externality.

With the threat of global climate change a high priority for policymakers around the world, policies to promote renewable energy technologies have come into fashion. Some of the most common policies focus on solar energy technologies, such as solar photovoltaics (PV) and solar hot water (SHW) heaters. Germany, Japan, and California have implemented large-scale subsidy policies to promote solar PV. Similarly, there are significant subsidy policies for SHW heaters in Germany, Austria, Sweden, the Netherlands, and France, and mandatory installation policies in Spain and Israel (Roulleau and Lloyd, 2008). Some of these policies began decades ago during the oil crises in the 1970s for energy security reasons, but both the number and extent of the policies have gained steam in recent years as part of broader efforts to reduce greenhouse gas emissions. New Zealand solar policy follows a similar pattern. From 1978 to 1982 New Zealand experimented with a SHW subsidy policy for energy security reasons. The NZ$500 subsidy policy was discontinued largely due to low take-up and poor system performance. With concerns about global climate change growing, New Zealand revived the solar subsidy program in 2002 with a NZ$300 subsidy towards the interest on a loan to finance the SHW installation, along with training and information policies. In 2006, the subsidy was increased to NZ$500 that could be taken directly as a grant or used towards the interest on a loan. One notable aspect of this new policy is that this subsidy will only be granted for purchases of systems that meet a cost-effectiveness threshold set by the Energy Efficiency and Conservation Authority (EECA) (EECA, 2007). New Zealand's policy has been met with some initial success in increasing diffusion of SHW systems, with SHW annual sales increasing from approximately 1000 in 2002 to 3500 in 2006 (EECA, 2006a). However, in the broader picture, SHW reduces both peak and total electricity demand by such an insignificant amount that the Ministry of Economic Development (MED) does not even examine SHW explicitly in its Energy Data File (MED, 2007a). Moreover, it remains unclear whether the 2006 policy changes will be successful in fostering a sustainable SHW market. There are several open questions pertaining to New Zealand SHW policy that have broader implications for SHW policy throughout the world. First, what does it mean for a SHW policy to be economic efficiency-improving? In other words, under what conditions would a SHW policy improve social welfare by reducing market failures? Second, is SHW in New Zealand currently financially attractive and if New Zealand is serious about promoting SHW, how large of a subsidy policy might be needed to ensure SHW is financially attractive? Third, what are the implications of large-scale SHW policies for electricity use and greenhouse gas emissions? Finally, would these policies be economic efficiency-improving? Previous publications that address the economics of SHW policy in New Zealand (e.g., EECA (2006a), EHMS (2006), EECA (2001), Sumner (2004), and McChesney (2005)) have provided useful technical overviews of the financial attractiveness of individual systems or examined the maximum technical potential for solar in New Zealand. This paper aims to address the questions posed above by presenting an economic framework for examining SHW policy based on market failures, and then using this framework as guidance for an economic analysis of several large-scale SHW policies. The rest of this paper is organized as follows. Section 2 provides this framework for examining the economic efficiency of SHW markets. Section 3 contains an analysis of the financial attractiveness of typical SHW systems to New Zealand consumers. Section 4 examines the implications of several larger-scale SHW policies than the current EECA policies. Section 5 concludes.

With the increased interest in renewable energy policies to meet long-run greenhouse gas emission reduction goals, understanding the implications and economic merits of policies to promote SHW is a critical task for policymakers. This paper provides guidance to policymakers looking to understand the economic motivation for SHW policy, and applies this economic framework to examine large-scale policies to promote SHW. Both the economic framework and the policy modeling are most relevant to New Zealand policy, but they provide a methodology for applications around the world. The investigation into the economic efficiency of SHW policy points to the critical importance of the global climate change externality underpinning the rationale for policy. This is particularly salient to policy in New Zealand, for a successful economy-wide greenhouse gas cap-and-trade program would internalize this externality, removing much of the motivation for SHW policy. Energy security, learning-by-doing, and average-cost pricing market failures provide much weaker motivation than the environmental externality. The examination of large-scale SHW policies indicates that even under the most extreme case – mandated SHW systems on all homes – SHW will still only reduce demand by 9% of the 2006 New Zealand electricity consumption. Moreover, policies mandating SHW systems on all homes and all new homes do not appear to be justifiable on economic efficiency grounds. However, SHW systems are currently marginally financially attractive with an IRR of 10% for a typical family home. The IRR increases to a very attractive 18% for family homes with a substantial subsidy of NZ$1500, which was chosen to match the increase in the upper bound of the range of prices between 2001 and 2006. The modeling results indicate that a large-scale subsidy program in concert with informational policies that lead to a sustainable SHW market could be economic efficiency-improving under reasonable assumptions of the magnitude of the environmental externality. This result is quite robust to most major parameters, but is dependent on the assumed form of diffusion. These results imply that if New Zealand policymakers do not implement a cap-and-trade policy, then a large-scale subsidy and informational policy to promote SHW may be worth considering. Future research may shed light on the importance of the average-cost pricing market failure, which could provide motivation for solar policy absent a climate change externality. On the other hand, shifting to real-time-pricing or time-of-use pricing may internalize this market failure, and provide greater benefits for load-management and reducing peak loads. Finally, broadening the scope of SHW policies to commercial and industrial buildings may increase the total potential for energy savings from SHW systems.